Article

A ‘dynamic’ landscape of fear: prey responses to spatiotemporal variations in predation risk across the lunar cycle

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Abstract

Ambiguous empirical support for ‘landscapes of fear’ in natural systems may stem from failure to consider dynamic temporal changes in predation risk. The lunar cycle dramatically alters night-time visibility, with low luminosity increasing hunting success of African lions. We used camera-trap data from Serengeti National Park to examine nocturnal anti-predator behaviours of four herbivore species. Interactions between predictable fluctuations in night-time luminosity and the underlying risk-resource landscape shaped herbivore distribution, herding propensity and the incidence of ‘relaxed’ behaviours. Buffalo responded least to temporal risk cues and minimised risk primarily through spatial redistribution. Gazelle and zebra made decisions based on current light levels and lunar phase, and wildebeest responded to lunar phase alone. These three species avoided areas where likelihood of encountering lions was high and changed their behaviours in risky areas to minimise predation threat. These patterns support the hypothesis that fear landscapes vary heterogeneously in both space and time.

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... We present a framework for understanding dynamic landscapes of fear (dynamic LOFs) [11,35] to guide future research on how prey perceive and respond to predation risk across both space and time simultaneously (Figures 1 and 3). The dynamic LOF integrates temporal variation and spatial heterogeneity to derive predictions about prey behavioral decision-making (e.g., distribution, activity levels, vigilance, association patterns [11,33,36]) and its potential consequences for individual fitness [32], species interactions and coexistence [37], and broader ecological processes [38]. ...
... We might expect spatial variation in predation risk perception to impose strong costs on prey if antipredator behaviors interfere with foraging opportunities, with possible cascading effects of predator avoidance on other trophic levels [2,3]. However, temporal cycles of predator activity may enable prey to modulate their spatial activity in time, for instance, by utilizing temporal refuges to access otherwise dangerous areas [33,35,36]. If so, then strong antipredator responses might not trigger non-consumptive effects [32,37] or behaviorally mediated trophic cascades [38] (Figure 2 and Table 1). ...
... Lunar cycles Lunar cycles moderate nocturnal predator success and prey vulnerability via light levels [50]. For visual animals, full-moon nights can aid predators in detecting prey [47] and/or prey in detecting predators [35]. Periodicity in nocturnal brightness can affect predator space use, activity, and hunting success; for example, noctule bats (Nyctalus noctula) hunt in forests on dark nights and open grasslands on bright nights [51]. ...
Article
The landscape of fear (LOF) concept posits that prey navigate spatial heterogeneity in perceived predation risk, balancing risk mitigation against other activities necessary for survival and reproduction. These proactive behavioral responses to risk can affect individual fitness, population dynamics, species interactions, and coexistence. Yet, antipredator responses in free-ranging prey often contradict expectations, raising questions about the generality and scalability of the LOF framework and suggesting that a purely spatial, static LOF conceptualization may be inadequate. Here, we outline a ‘dynamic’ LOF framework that explicitly incorporates time to account for predictable spatiotemporal variation in risk–resource trade-offs. This integrated approach suggests novel predictions about predator effects on prey behaviors to refine understanding of the role predators play in ecological communities.
... Likewise, group size can be defined as the number of detected individuals for a certain species at a particular time and lick (Clayton and MacDonald, 1999;and Journeaux et al., 2018). Duration of a species or an individual of the given species to a mineral lick is regarded as the visitation duration, even though this duration is highly dependent on the time interval used by the researchers in minimizing the temporal autocorrelation of photographic events (Palmer et al., 2017;Bernard et al., 2019;and Griffiths et al., 2020). Henceforth, only the individuals of the same species that are detected at a specific lick beyond the fixed time intervals (e.g., 30 mins or 60 mins) are assumed as non-identical individuals in recent studies (e.g., Matsubayshi et al., 2007a andMatsuda et al., 2015;. ...
... Nonetheless, this species, together with Red Brocket Deer (Mazama americana), Paca (Cuniculus paca), and Brazilian Porcupine (Coendou prehensilis) were verified by Griffiths et al., (2020) to visit the mineral licks in Peruvian Amazonia forests, during the nights with high nocturnal luminosity, individually and/or as a group, and vice versa. The current population density of predator species is the main cause of this contradiction in findings, in which a low abundance of predator allows the prey species to forage and geophagy at the given mineral licks without fear of being hunted, while high predator abundance puts these prey species at a high predation risk when using the licks, during the nights with high lunar illumination, and vice versa (Prugh and Golden, 2014;Traill et al., 2016;and Palmer et al., 2017). Therefore, the degree of influence of the seasonal change in nocturnal luminosity towards group size, visitation duration and frequency of a specific species is dictated by the prey-predator relationship presented at a certain mineral lick. ...
... Hourly changes in ambient temperature, cloud cover, luminosity, and precipitation only have prominent effects on certain species, while the influence of wind speed is detrimental on the visitation frequencies of terrestrial mammals at the licks (Tankersley and Gasaway, 1983;and Link et al., 2011). Variation in the moon phase, as well as the hourly variation in weather condition, can modify the nocturnal luminosity emitted to a certain mineral lick and at a given time (Prugh and Golden, 2014;and Palmer et al., 2017). Then, the feeding guild defines the role of a given mammal species as prey or predator, which results in a prey-predator relationship between two or more species, and then this relationship can be influenced significantly by the anthropogenic disturbance (Hon and Shibata, 2013;and Matsuda et al., 2015). ...
Chapter
This chapter reviews relevant past studies and publications to provide a holistic understanding of the relationship between terrestrial mammals and mineral licks in the tropical rainforest ofMalaysia. Sodium deficiency in the vegetation of inland tropical rainforest has caused the terrestrial mammals with plants-based diets to depend on both natural and artificial licks for sodium intake on a regular basis. Mineral licks help terrestrial mammals to maintain homeostasis of minerals and neutralize toxicities accumulated in their bodies. Presently, 56 species of terrestrial mammals are observed at the mineral licks in Malaysia, where ungulates remain as the main visitors of the local licks. However, arboreal primate, rodent, fruit-eating bat, and predator species can be detected at the given licks as well, because their respective visitation pattern can be affected by various explanatory variables. These variables are categorized into five major groups in this chapter, such as the 1) Anthropogenic disturbance; 2) Bio-physiochemical properties; 3) Weather conditions 4) Species traits, and; 5) Surrounding habitat conditions, of the licks. This chapter manages to identify the complex interrelationships between the given explanatory variables in impacting the mammalian visitation patterns to mineral licks in Malaysia. Visitation patterns of terrestrial mammals to mineral licks are frequently investigated by researchers through seven different aspects, for both individual species and all species as a whole. These parameters are: 1) Diel activity pattern; 2) Species composition; 3) Group size; 4) Species diversity; 5) Relative abundance; 6) Visitation duration, and; 7) Visitation frequency of detected species. However, the research trend of this field of study focuses on employing explanatory variables that are frequently applied by researchers, thus the degrees of influences of many explanatory variables towards mammalian visitation pattern to the licks in Malaysia remain uncertain at this moment. Besides that, several variables with potential impacts on the given matter have been identified in this chapter as well. In other words, various opportunities remain available for future researchers to fill up research gaps, as highlighted in this chapter.
... Alternatively, behaviorallymediated trophic cascades may be generated by increased vigilance at the expense of foraging behavior, reducing deer impacts on plants and soils as described above even if deer continued to visit 'risky' sites. However, we predicted that a trophic cascade would not materialize if deer responded to perceived predation risk by altering spatiotemporal patterns of habitat use, visiting risky sites at a rate comparable to safe locations but only during times of day perceived less dangerous based on experience with resident wolves (see Palmer et al. 2017;Kohl et al. 2018;Smith et al. 2019). ...
... Behavioral responses to temporal fluctuations in predation risk have been studied for decades (reviewed in Kronfeld-Shor and Dayan 2003), but only recently have we begun examining prey temporal risk-sensitivity within a spatially structured risk framework (i.e., exploring the idea that spatially structured predation risk that is perceived as more or less threatening depending on temporal fluctuations in risk from the same predator; Palmer et al. 2017;Kohl et al. 2018;Smith et al. 2019). Adaptive allocation of foraging across the landscape during periods of high and low predator activity is proposed to be a mechanism by which prey mitigate fitness trade-offs, reducing the ecological impact of the landscape of fear (Kohl et al. 2018). ...
... Our work provides the first demonstration of spatiotemporal sensitivity to wolf predation risk in white-tailed deer and is one of the first studies to examine how this spatiotemporal sensitivity may impact community dynamics in a trophic cascade context. Work in other carnivore-ungulate systems suggests these types of prey may be sensitive to risk structured across both time and space (Palmer et al. 2017;Kohl et al. 2018;Smith et al. 2019). In our system, deer navigation of this dynamic landscape of fear appears to have reduced the cascading impact of non-consumptive predator effects; the weakness of this pathway may provide a potential explanation for why trophic cascades often fail to materialize in terrestrial mammalian systems (Borer et al. 2005). ...
Article
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The mere threat of predation may incite behavioral changes in prey that lead to community-wide impacts on productivity, biodiversity, and nutrient cycling. The paucity of experimental manipulations, however, has contributed to controversy over the strength of this pathway in wide-ranging vertebrate systems. We investigated whether simulated gray wolf (Canis lupus) presence can induce behaviorally-mediated trophic cascades, specifically, whether the ‘fear’ of wolf olfactory cues alone can change deer foraging behavior in ways that affect plants and soils. Wolves were recently removed from the Cedar Creek Ecosystem Science Reserve (Minnesota, USA), such that consumptively mediated predator effects were negligible. At 32 experimental plots, we crossed two nested treatments: wolf urine application and herbivore exclosures. We deployed camera traps to quantify how white-tailed deer (Odocoileus virginianus) adjusted their spatiotemporal habitat use, foraging, and vigilance in response to wolf cues and how these behavioral changes affected plant productivity, plant communities, and soil nutrients. Weekly applications of wolf urine significantly altered deer behavior, but deer responses did not cascade to affect plant or soil properties. Deer substantially reduced crepuscular activity at wolf-simulated sites compared to control locations. As wolves in this area predominantly hunted during mornings and evenings, this response potentially allows deer to maximize landscape use by accessing dangerous areas when temporal threat is low. Our experiment suggests that prey may be sensitive to ‘dynamic’ predation risk that is structured across both space and time and, consequentially, prey use of risky areas during safe times may attenuate behaviorally-mediated trophic cascades at the predator–prey interface.
... both nocturnal and diurnal species (Miller, 2006, Kronfeld-Schor et al., 2013, Owens & Lewis, 2018, with a wide range of effects on sleep patterns (Van Hasselt et al., 2020), reproduction (Foster, Heyward, & Gilmour, 2018;Gaston & Bennie, 2014;Jackson, 1985;York, Young, & Radford, 2014), predation risk (Griffin, Griffin, Waroquiers, & Mills, 2005;Haddock, Threlfall, Law, & Hochuli, 2019;Mougeot & Bretagnolle, 2000;Palmer, Fieberg, Swanson, Kosmala, & Packer, 2017), and foraging behavior (Kotler, Brown, Mukherjee, Berger-Tal, & Bouskila, 2010;Ravache et al., 2020;Roeleke, Teige, Hoffmeister, Klingler, & Voigt, 2018;San-jose et al., 2019;Da Silva, Valcu, & Kempenaers, 2015). Previous work has shown that artificial night light can disrupt these predictable lunar cues in insects (Altermatt & Ebert, 2016), amphibians (Baker & Richardson, 2006), reptiles (Brei, Pérez-Barahona, & Strobl, 2016), mammals (Spoelstra et al., 2015), and birds (Rodríguez et al., 2017). ...
... Our study confirms earlier observations of lunar-associated behavior in nightjars (see below), but it remains to be shown whether circadian and circalunar rhythms play a role.Variation in moonlight (affected by the moon's altitude and phase) is known to influence predation risk, foraging behavior, habitat use and reproduction of many terrestrial taxa(Kronfeld- Schor et al., 2013). Predator avoidance is typically observed in prey species around full moon(Griffin et al., 2005;Harmsen, Foster, Silver, Ostro, & Doncaster, 2011;Navarro-Castilla & Barja, 2014;Palmer et al., 2017;Smith, Tulp, Schekkerman, Gilchrist, & Forbes, 2012), whereas other taxa exploit better ...
Article
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Biological rhythms of nearly all animals on earth are synchronized with natural light and are aligned to day‐and‐night transitions. Here, we test the hypothesis that the lunar cycle affects the nocturnal flight activity of European Nightjars (Caprimulgus europaeus). We describe daily activity patterns of individuals from three different countries across a wide geographic area, during two discrete periods in the annual cycle. Although the sample size for two of our study sites is small, the results are clear in that on average individual flight activity was strongly correlated with both local variation in day length and with the lunar cycle. We highlight the species’ sensitivity to changes in ambient light and its flexibility to respond to such changes in different parts of the world. Predictable, recurring environmental changes, such as the daily light‐dark cycles, influence both nocturnal and diurnal species and have wide‐ranging effects on their behavior. We describe daily activity patterns of European Nightjars from three extremes of the species’ breeding range, during two discrete periods in the annual cycle. Our study highlights the species’ sensitivity to changes in ambient light and its flexibility to respond to such changes in different parts of the world.
... However, past studies have suggested prey may in fact be more likely to avoid specific habitats or landscape features that increase their vulnerability to predation (Hopcraft, Sinclair, & Packer, 2005;Kauffman et al., 2007;Kohl et al., 2018). Predation risk may also vary over time, such as increase during times of the day when predators are more active or have higher hunting success rates (Gehr et al., 2018;Kohl et al., 2018;Palmer, Fieberg, Swanson, Kosmala, & Packer, 2017). In this context, Moll et al. (2017) recently recommended the use of multiple metrics in studies of predation risk. ...
... Recent work on the responses of prey to predators has highlighted the importance of time in modulating spatial relationships between prey movements and predation risk (Creel et al., 2008;Palmer et al., 2017). In particular, Kohl et al. (2018) hour of the day. ...
Preprint
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The extent to which prey space use actively minimises predation risk continues to ignite controversy. Methodological reasons that have hindered consensus include inconsistent measurements of predation risk, biased spatiotemporal scales at which responses are measured, and lack of robust null expectations. We addressed all three challenges in a comprehensive analysis of the spatiotemporal responses of adult female elk ( Cervus elaphus ) to the risk of predation by grey wolves ( Canis lupus ) during winter in northern Yellowstone, USA. We quantified spatial overlap between the winter home ranges of GPS-collared elk and three measures of predation risk: the intensity of wolf space use, the distribution of wolf-killed elk and vegetation openness. We also assessed whether elk varied their use of areas characterised by more or less predation risk across hours of the day, and estimated encounter rates between simultaneous elk and wolf pack trajectories. We determined whether observed values were significantly lower than expected if elk movements were random with reference to predation risk using a null model approach. Although a small proportion of elk did show a tendency to minimise use of open vegetation at specific times of the day, overall we highlight a notable absence of spatiotemporal response by female elk to the risk of predation posed by wolves in northern Yellowstone. Our results suggest that predator-prey interactions may not always result in strong spatiotemporal patterns of avoidance.
... Camera trap monitoring within each protected area provides continuous, fine-scale data on mammal and bird species >1 kg (O'Connell et al., 2010;Wearn & Glover-Kapfer, 2017). Data generated by Snapshot Safari are being used by government agencies, conservation organizations, protected area managers, and academic institutions to understand patterns of wildlife movement, behavior, and interactions and to examine how these trends change across environmental gradients and in the face of anthropogenic perturbations (e.g., Anderson et al., 2016;Swanson et al., 2016b;Palmer et al., 2017Palmer et al., , 2019Allen et al., 2018;Muzena et al., 2019). ...
... Due to the image-level labeling of the camera trap captures, another drawback with our current approach is that our AI cannot identify more than one species per capture event. While <2% of Snapshot Safari images overall contain multiple species (Norouddezzah et al., 2018;Willi et al., 2019; Figure 2D), these images contain valuable information about species interactions such as mutualisms, facilitation, competition, and predator-prey relationships (e.g., Palmer et al., 2017;Beaudrot et al., 2020). ...
Article
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Camera traps - remote cameras that capture images of passing wildlife - have become a ubiquitous tool in ecology and conservation. Systematic camera trap surveys generate ‘Big Data’ across broad spatial and temporal scales, providing valuable information on environmental and anthropogenic factors affecting vulnerable wildlife populations. However, the sheer number of images amassed can quickly outpace researchers’ ability to manually extract data from these images (e.g., species identities, counts, and behaviors) in timeframes useful for making scientifically-guided conservation and management decisions. Here, we present ‘Snapshot Safari’ as a case study for merging citizen science and machine learning to rapidly generate highly accurate ecological Big Data from camera trap surveys. Snapshot Safari is a collaborative cross-continental research and conservation effort with 1500+ cameras deployed at over 40 eastern and southern Africa protected areas, generating millions of images per year. As one of the first and largest-scale camera trapping initiatives, Snapshot Safari spearheaded innovative developments in citizen science and machine learning. We highlight the advances made and discuss the issues that arose using each of these methods to annotate camera trap data. We end by describing how we combined human and machine classification methods (‘Crowd AI’) to create an efficient integrated data pipeline. Ultimately, by using a feedback loop in which humans validate machine learning predictions and machine learning algorithms are iteratively retrained on new human classifications, we can capitalize on the strengths of both methods of classification while mitigating the weaknesses. Using Crowd AI to quickly and accurately ‘unlock’ ecological Big Data for use in science and conservation is revolutionizing the way we take on critical environmental issues in the Anthropocene era.
... which has operated continuously since 2010, is a flagship example of a long-term camera-trap monitoring programme. Over the past decade, this survey has gathered unprecedented longitudinal data that have substantially enhanced our understanding of the seasonal and inter-annual dynamics of the Serengeti ecosystem 16,19,20 . Projects of this magnitude have become increasingly common across eastern and southern Africa 18 and around the world 1 . ...
... This need is likely to grow exponentially over the coming decades as more monitoring sites are set up. Although only one or two experts are needed to validate each wildlife image, it is common practice that multiple (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) volunteers or citizen scientists look at each image to produce a high-accuracy 'consensus' classification (~97% accurate compared to expert identifications 16 ). This duplication of effort needed to generate accurate results using volunteers further perpetuates the classification bottleneck. ...
Article
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Camera trapping is increasingly being used to monitor wildlife, but this technology typically requires extensive data annotation. Recently, deep learning has substantially advanced automatic wildlife recognition. However, current methods are hampered by a dependence on large static datasets, whereas wildlife data are intrinsically dynamic and involve long-tailed distributions. These drawbacks can be overcome through a hybrid combination of machine learning and humans in the loop. Our proposed iterative human and automated identification approach is capable of learning from wildlife imagery data with a long-tailed distribution. Additionally, it includes self-updating learning, which facilitates capturing the community dynamics of rapidly changing natural systems. Extensive experiments show that our approach can achieve an ~90% accuracy employing only ~20% of the human annotations of existing approaches. Our synergistic collaboration of humans and machines transforms deep learning from a relatively inefficient post-annotation tool to a collaborative ongoing annotation tool that vastly reduces the burden of human annotation and enables efficient and constant model updates.
... day/night/dawn/dusk) and/or year (e.g. seasons), can influence the probability of predation process stages depending on predator hunting technique (Cozzi et al., 2012), changes in seasonal prey abundance (Kittle et al., 2016), environmental conditions (Van Orsdol, 1984) and prey activity patterns (Palmer et al., 2017). Where on the landscape predation process stages occur can be affected by prey distribution (Lendrum et al., 2018), the location of key landscape features (Gese et al., 1996) and habitat attributes that increase prey vulnerability (Hopcraft et al., 2005). ...
... Several external factors may have influenced results in this study. First, the lunar phase (full moon) during nocturnal observations, for although lions do not alter their movement activities under moonlight (Preston et al., 2019), prey species often do, with those relying on non-visual cues typically reducing activity (Prugh & Golden, 2014), and others increasing their use of high lion-encounter areas (wildebeest and zebra) or congregating in greater abundance in low-risk areas (buffalo and gazelle; Palmer et al., 2017). African lions also have higher hunting success on nights when the moon is absent or obscured, in open (Funston et al., 2001;Packer et al., 2011;Van Orsdol, 1984) and wooded areas (Preston et al., 2019). ...
Article
Predation is a fundamental ecological process influencing the distribution and abundance of animal populations and underlying how prey species perceive risk. The predation process is composed of four sequential stages – search, encounter, attack and kill – each of which has been used to describe risk across the landscape. Here, we used direct observational data of free‐ranging, radio‐collared African lions in Serengeti National Park's western corridor to (1) investigate daily and seasonal predation stage probabilities and (2) using two analytical approaches, compare four mechanisms – prey distribution, intra‐specific competition, spatially anchored landscape features and predator hunting method – that potentially drive spatial predation stage patterns. Results showed that lions encountered potential prey at night significantly less than during diurnal or crepuscular periods. Nocturnal observations were predominantly during full‐moon phases, so if this lower nocturnal encounter rate was due to moon phase it may contribute to lions' typically poor full‐moon hunting success. Predation stage probabilities did not differ between seasons despite high variability in seasonal prey abundance. Spatially, lions encountered potential prey in prey‐rich, open areas near water and spatial range centres. Compared with available areas within seasonal ranges, lion attacks were more likely where prey abundance was high, and kill locations were associated with prey‐rich areas near water and range centres, collectively suggesting opportunistic hunting. However, compared with preceding predation stage locations, attacks occurred near range peripheries and kills where hunting cover was greater, suggesting ambush predation. Our results indicate substantial temporal and spatial variation across the different stages of the predation process. They also highlight first, that results can vary in important ways depending on how analyses are approached, and second, that understanding predator‐prey dynamics depends on analyses of the different stages of predation. This study used direct observational data of African lions in Serengeti National Park's western corridor to (1) investigate daily and seasonal predation stage probabilities and (2) compare, using two analytical approaches, four mechanisms ‐ prey distribution, intra‐specific competition, spatially anchored landscape features and predator hunting method ‐ that potentially drive spatial predation stage patterns. Results indicate substantial temporal and spatial variation across the different stages of the predation process, and highlight that results can vary in important ways depending on how analyses are approached, and that understanding predator‐prey dynamics depends on analyses of the different stages of predation.
... The threat of predation is not uniform in natural systems but varies both spatially and temporally due to changes in environmental conditions (Penteriani et al. 2013;Palmer et al. 2017). We found that both seasonal and interannual bottlenecks in water availability corresponded with increased prey presence (i.e., macropods, pigs, cattle, and buffalo) at savanna waterholes, similar to previous findings from Africa (Thrash et al. 1995). ...
... Predation threat can also vary with changes in night-time illumination (Harmsen et al. 2011;Penteriani et al. 2011Penteriani et al. , 2013Palmer et al. 2017). We found that dingo activity around waterholes increased on moonless nights, suggesting that dingo hunting success may improve under low light conditions, as has been shown for other savanna predators (e.g., lions: Funston et al. 2001;Packer et al. 2011). ...
Article
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When exotic species are introduced to new environments, they often have a competitive advantage over native species. In northern Australia, pigs, cattle, and water buffalo have established widespread, feral populations. As ungulates have high water requirements, they typically congregate near waterpoints. We used a fencing experiment to test whether native macropods preferentially visited savanna waterholes where large ungulates were excluded. We also investigated whether water scarcity affected the visitation behaviour and temporal activity patterns of herbivores at waterholes and whether increasing prey aggregation at waterholes increased dingo presence. We found that macropods did not use fenced waterholes preferentially over unfenced ones. Cattle presence at waterholes increased as water became scarce, while macropod and pig presence peaked in the middle of the dry season. Macropod activity declined rapidly at the end of the dry season when cattle activity was greatest, suggesting that macropods may avoid waterholes in areas utilised by cattle when competition for resources is high. Macropods and all ungulates visited waterholes more during a drought year compared to an average rainfall year. Despite increasing prey activity, dingo presence at waterholes did not increase when water became scarce. However, dingo presence increased significantly on moonless nights. Our results suggest that competition between macropods and ungulates may intensify during periods of water scarcity. Climate change and pastoral intensification are likely to increase competition for resources between ungulates and macropods in Australian savannas, potentially threatening macropod populations across the landscape in the future. Significance statement In northern Australia, feral populations of pigs, cattle, and water buffalo compete with native wildlife for access to water sources. As interspecific competition favours species with a size advantage, we tested whether kangaroos and wallabies (macropods) preferentially use waterholes where large ungulates (cattle and buffalo) were excluded. We found that macropods avoided waterholes when cattle presence was high but did not preferentially use waterholes where livestock were excluded. When water scarcity peaked during a drought, macropods and all three feral ungulate species visited waterholes more. However, increased prey presence at waterholes during the drought did not correspond with increased predator (dingo) presence. Our study advances the understanding of behavioural interactions between invasive and native species at important shared resources, and how this may affect wildlife conservation in an increasingly unpredictable environment.
... Using the disturbance layer, we then calculated the Euclidian distance to disturbance at each mule deer GPS location. Because animal responses to human disturbance can vary depending on spatial scales, landscape features and intensity of disturbance (Northrup et al., 2015;Palmer et al., 2017;Polfus et al., 2011;Sawyer et al., 2009), we also summarized metrics of exposure to human disturbance for each collared animal in each year while they were on winter range ( Table 1). Metrics of exposure to human disturbance for each individual included the number of days spent within 50, 100 and 200 m of a disturbance feature, mean distance to disturbance of all locations throughout the winter, the percent of disturbance within each home range and density of disturbance within each home range. ...
... Similar to other studies Stankowich, 2008;Wyckoff et al., 2018), animals increased movement rates near human disturbance overall but with much variation among individuals and such movements failed to influence nutritional condition over winter; thus, suggesting that animals were able to, in part, mitigate energetic costs of perceived risk in the short term. Prey species often adjust behaviours on multiple spatiotemporal scales to mediate the lethal and nonlethal effects of predation, allowing populations to persist among a dynamic 'landscape of fear' (Gaynor et al., 2019;Latombe et al., 2014;Middleton et al., 2013;Palmer et al., 2017;Proffitt et al., 2013). For example, animals can mitigate risk effects of human disturbance by dampening behaviours of perceived risk at night, when disturbance is attenuated (Gaynor et al., 2018;Northrup et al., 2015). ...
Article
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According to risk‐sensitive foraging theory, animals should make foraging decisions that balance nutritional costs and gains to promote fitness. Human disturbance is a form of perceived risk that can prompt avoidance of risky habitat over acquisition of food. Consequently, behavioral responses to perceived risk could induce nutritional costs. Population declines often coincide with increases in human disturbance, which likely is associated with direct and indirect habitat loss. Nevertheless, behavioral and physiological responses to perceived risks associated with human disturbance could be an added nutritional deficit with population‐level repercussions. Using GPS‐collar data from three populations of migratory mule deer (Odocoileus hemionus) exposed to a gradient of established industrial energy development on winter ranges where direct and indirect habitat loss were well documented, we evaluated whether exposure and behavioral responses to human disturbance alter changes in nutritional condition (i.e., fat reserves) over winter. Although animals exhibited behaviors indicative of perceived risk of human disturbance, such as increased movement rates and avoidance of infrastructure, exposure and behavioral responses to human disturbance had little to no measurable effect on fat loss over a winter. Instead, catabolism of fat reserves occurred primarily as a function of the amount of fat animals had entering winter, suggesting that, in the short‐term, animals were able to mitigate the energetic costs of perceived risk of human disturbance over winter. Animals, however, did not appear to overcome persistent food limitations, and animals with less food availability lost more fat over winter. Our findings heed caution in using short‐term behavioral and physiological responses to inform long‐term nutritional consequences of human disturbance. Although animals appear to mitigate the energetic costs of perceived risk, food limitations exacerbated by broader‐scale avoidance of food near human disturbance may be the primary pathway causing the frequently observed population declines following human disturbance to pristine landscapes.
... Perceived predation risk is not a fixed spatial pattern and typically changes across much shorter timescales than forage quantity or quality. Large herbivores are expected to adaptively change their habitat selection across the diel cycle as local predation risk in specific habitats increases or decreases, for example, due to changes in the activity of predators (Kohl et al., 2018;Palmer et al., 2017;Veldhuis et al., 2020). Masai pastoralist activities in village lands add to this dynamic landscape of fear. ...
... To minimize double-counting of individuals that remained within the camera's field of view for prolonged periods, we used 10-min time slots in which we used the image within each sequence with the most individuals for scoring. This ensures statistical independence of measurements as individual animals are unlikely to stay in the same place (in front of cameras) longer than 4-5 min in these systems (Palmer et al., 2017). ...
Article
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The rapid expansion of human populations in East Africa increases human‐wildlife interactions, particularly along borders of protected areas (PAs). This development calls for a better understanding of how human‐modified landscapes facilitate or exclude wildlife in savannas and whether these effects change through time. Here, we used camera traps to compare the distribution of 13 large herbivore species in Serengeti National Park with adjacent village lands used by livestock and people at both seasonal and diel cycle scales. The results show that body weight and feeding guild predict habitat use. Smaller sized grazers and mixed‐feeders occurred more in village lands than larger herbivores. Across seasons, mixed‐feeders and large browsers used edge areas year‐round, while grazers were largely excluded during the dry season. At the diel cycle scale, wild herbivores' activity shifts towards the night in village lands compared to the protected area. A closer look revealed that wildebeest (Connochaetes taurinus) and zebra (Equus quagga) mainly used village lands from pre‐dusk to midnight when pastoralists and their livestock were absent. Wildebeest and zebra activity in village lands peaked around dusk, which overlapped with peaks in predator activity. These results suggest that edge areas of PAs can provide valuable habitat to native herbivores. Intensive use of village lands by grazing herbivores during the wet season – particularly at night – suggests grazers benefit from high‐quality grazing lawns and increased safety from predators during part of the year. Herbivores that (also) forage on browse can benefit year‐round from both food availability and decreased predation risk. We further note that excluding nighttime observations in similar studies may underestimate the use of edge areas by wildlife. Understanding how edge areas fit into the risk‐resource landscape will help identify the unique benefits of edge areas to wildlife and promote coexistence of people and wildlife around protected areas.
... Since predation risk can vary over space (e.g. risky vs. safe habitats) and time (e.g. times of day), prey commonly face situations with varied levels of risk (Hebblewhite et al. 2005, Kauffman et al. 2007, Laundré et al. 2010, Palmer et al. 2017. Natural selection may choose for prey that are able to perceive this heterogeneity in risk and to react accordingly in a way that minimizes fitness consequences of the costs associated with anti-predator behaviours (Lima andDill 1990, Lima 1998). ...
... The landscape of fear concept assumes that a prey individual moves across a landscape with various levels of risk in keeping with the risk-related trade-off (Laundré et al. 2010). Prey are therefore expected to adjust their proactive behaviours to the spatio-temporal variations in predation risk (Laundré et al. 2001, Palmer et al. 2017) and the magnitude of the baseline predation risk ('threat sensitivity hypothesis'; Helfman 1989). ...
Thesis
Les effets des changements globaux sur les habitats naturels sont de plus en plus perceptibles, et comprendre comment les animaux y répondent est nécessaire pour une meilleure gestion de leurs populations. C’est en effet à travers leur impact sur l’environnement, et essentiellement sur les habitats, que les activités humaines ont souvent le plus grand effet sur les écosystèmes, à travers le changement climatique, la fragmentation, la destruction de l'habitat, les changements dans l'utilisation des terres ou la surexploitation des ressources. Les ongulés constituent un exemple marquant de progression numérique et spatiale d’une guilde d’espèces dans des écosystèmes impactés par l’Homme. Cet essor démographique est à l’origine d’un nombre croissant d’interactions entre Homme et faune et place la gestion de ces espèces au cœur des préoccupations des politiques publiques. Dans ce contexte, j’ai étudié cinq espèces de grands ongulés sauvages : le chamois, le mouflon, le bouquetin, le chevreuil et le cerf, dans le cadre du projet Mov-It (Ungulates MOVing across heterogeneous landscapes: identifying behavioural processes linking global change to spatially-explicIT demographic performance and management), soutenu par l’Agence Nationale de la Recherche (ANR). Dans un premier temps, je mets en évidence les liens entre variations intraspécifiques de la taille du domaine vital saisonnier des ongulés, le paysage (i.e. les ressources, le risque et l’hétérogénéité) et les traits d’histoire de vie de ces espèces. Je me suis ensuite intéressée plus particulièrement à l’influence des structures linéaires anthropiques et naturelles du paysage sur l'utilisation individuelle de l'espace. Je montre ainsi que les grands herbivores utilisent des structures linéaires du paysage pour délimiter leur domaine vital mensuel, mais que l'importance relative de ces structures linéaires dans la délimitation du domaine vital mensuel diminuait à mesure que leur densité augmentait dans le paysage local. Je mets également en évidence le caractère risqué des structures anthropiques pour les ongulés, en particulier l'effet de l'intensité de l’utilisation humaine de ces structures sur le nombre de traversées par les mouflons. Enfin, l’importance de la prise en compte du paysage du risque et des ressources sur l’organisation sociale est démontré. En effet, la formation de dyades (i.e. paires d’individus) est plus probable dans les milieux ouverts riche en ressources et lorsque le risque, incluant prédation et dérangement, est le plus fort (i.e. le jour). L’ensemble des résultats présentés dans ce travail de thèse a permis d’améliorer notre compréhension des effets de la structure du paysage et de la socialité sur la sélection d’habitat et le mouvement chez différentes espèces d’ongulés.
... Prior validation of volunteer classifications against expert-identified subset of the data demonstrated the consolidated classifications agreed with the 'correct' classifications 97% of the time, and we improved this accuracy to 99% by limiting analyses to classifications with at least 60% agreement among volunteers (Swanson et al. 2016b). To prevent inflated counts of animals remaining in front of the camera traps for extended periods (e.g., triggering multiple images), consecutive captures from a camera within 10-minutes of each other containing the same species were consolidated into a single capture event (Palmer et al. 2017). ...
... Territory boundaries were defined as the 75% volume contour of kernel density estimates derived from VHF radio collar telemetry relocations; these values were weighted by both the number of lions in the pride and the duration of pride persistence in years between 2009-2014. The Serengeti Lion Project has traditionally used a 75% threshold(Mosser et al. 2009, Palmer et al. 2017) because of the potential sensitivity of kernel density estimates to sample size(Harris et al. 1990). Where territories overlapped, these values were summed at a 1 km 2 scale, and the final values were scaled based on the mean value of lion density across the entire study area. ...
Article
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Understanding the role of species interactions within communities is a central focus of ecology. A key challenge is to understand variation in species interactions along environmental gradients. The stress‐gradient hypothesis posits that positive interactions increase and competitive interactions decrease with increasing consumer pressure or environmental stress. This hypothesis has received extensive attention in plant community ecology, but only a handful of tests in animals. Furthermore, few empirical studies have examined multiple co‐occurring stressors. Here we test predictions of the stress‐gradient hypothesis using the occurrence of mixed‐species groups in six common grazing ungulate species within the Serengeti‐Mara ecosystem. We use mixed‐species groups as a proxy for potential positive interactions because they may enhance protection from predators or increase access to high quality forage. Alternatively, competition for resources may limit the formation of mixed‐species groups. Using more than 115,000 camera trap observations collected over five years, we found that mixed‐species groups were more likely to occur in risky areas (i.e., areas closer to lion vantage points and in woodland habitat where lions hunt preferentially) and during time periods when resource levels were high. These results are consistent with the interpretation that stress from high predation risk may contribute to the formation of mixed‐species groups, but that competition for resources may prevent their formation when food availability is low. Our results are consistent with support for the stress gradient hypothesis in animals along a consumer pressure gradient while identifying the potential influence of a co‐occurring stressor, thus providing a link between research in plant community ecology on the stress gradient hypothesis, and research in animal ecology on trade‐offs between foraging and risk in landscapes of fear.
... Predator hunting success may vary not only in space but on a diel cycle, and as such temporal variation in encounter and capture probabilities has long been appreciated as a significant component of predation risk patterns and predator-prey interactions across taxa (Hampton 2004, Hrabik et al. 2006, Ory et al. 2014, and more recently in large vertebrates (Palmer et al. 2017, Courbin et al. 2019, Smith et al. 2019a. Temporal patterns of wolf predation on moose, for example, are not constant throughout the day but are better predicted by wolf movement rates than light availability (Vander Vennen et al. 2016). ...
... Because vicuñas are reliant on visual cues to detect predators (and visual detection is reduced at night, limiting the efficacy of vigilance behaviors; Sarno et al. 2008), we assumed that intrinsic catchability given an encounter was a function of darkness, which we calculated as the inverse sun angle by time of day (package oce; Kelley and Richards 2018). Although moon illumination can also influence intrinsic risk as a function of darkness (Kotler et al. 2010, Packer et al. 2011, Prugh and Golden 2014, Palmer et al. 2017, we were primarily interested in broader diel patterns of predation behavior, whereby the night is always darker than the day regardless of lunar period. ...
Article
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Predator-prey games emerge when predators and prey dynamically respond to the behavior of one another, driving the outcomes of predator-prey interactions. Predation success is a function of the combined probabilities of encountering and capturing prey, which are influenced by both prey behavior and environmental features. While the relative importance of encounter and capture probabilities have been evaluated in a spatial framework, temporal variation in prey behavior and intrinsic catchability are likely to also affect the distribution of predation events. Using a single-predator-single-prey (puma-vicuña) system, we evaluated which factors predict predation events across both temporal and spatial dimensions of the components of predation by testing the prey-abundance hypothesis (predators select for high encounter probability) and the prey-catchability hypothesis (predators select for high relative capture probability) in time and space. We found that for both temporal and spatial analyses, neither the prey-abundance hypothesis nor the prey-catchability hypothesis alone predicted kill frequency or distribution; puma kill frequency was static throughout the diel cycle and pumas consistently selected a single habitat type when hunting, despite temporal and spatial variation in encounter rates and intrinsic catchability. Our integrated spatiotemporal analysis revealed that an interaction between time of day and habitat influences kill probability, suggesting that trade-offs in the temporal and spatial components of predation drive the probability of predation events. These findings reinforce the importance of examining both the temporal and spatial patterns of the components of predation, rather than unidimensional measures of predator or prey behavior, to comprehensively describe the feedbacks between predator and prey in the predator-prey game.
... Also, environments that favor parasites may suppress the distribution of their hosts locally, resulting in the absence of the host species from areas that may otherwise be optimal for their survival (Giannini, Chapman, Saraiva, Alves-dos-Santos, & Biesmeijer, 2013). Despite the potential importance of risk layers in shaping species distributions, they are rarely included in species distribution models because actual and perceived risks tend to be dynamic processes that are difficult to quantify (Palmer, Fieberg, Swanson, Kosmala, & Packer, 2017). ...
Book
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Ecologists develop species-habitat association (SHA) models to understand where species occur, why they are there and where else they might be. This knowledge can be used to designate protected areas, estimate anthropogenic impacts on living organisms and assess risks from invasive species or disease spill-over from wildlife to humans. Here, we describe the state of the art in SHA models, looking beyond the apparent correlations between the positions of organisms and their local environment. We highlight the importance of ecological mechanisms, synthesize diverse modelling frameworks and motivate the development of new analytical methods. Above all, we aim to be synthetic, bringing together several of the apparently disconnected pieces of ecological theory, taxonomy, spatiotemporal scales, and mathematical and statistical technique in our field. The first edition of this ebook reviews the ecology of species-habitat associations, the mechanistic interpretation of existing empirical models and their shared statistical foundations that can help us draw scientific insights from field data. It will be of interest to graduate students and professionals looking for an introduction to the ecological and statistical literature of SHAs, practitioners seeking to analyse their data on animal movements or species distributions and quantitative ecologists looking to contribute new methods addressing the limitations of the current incarnations of SHA models.
... The variety of Snapshot locations provides numerous opportunities to answer questions in wildlife ecology and conservation, test ecological hypotheses and analytical methods, and measure the impacts of anthropogenic disturbances across multiple spatiotemporal scales. For example, the data produced by the camera traps running continuously in the Serengeti provided the basis for papers on spatiotemporal partitioning [15][16][17] , behavioural interactions [18][19][20] , and advancing modelling techniques used with the camera trap data 11,19,21 . ...
Article
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Nature is experiencing degradation and extinction rates never recorded before in the history of Earth.1,2 Consequently, continuous large-scale monitoring programmes are critical, not only to provide insights into population trends but also to aid in understanding factors associated with altering population dynamics at various temporal and spatial scales.3 Continuous monitoring is important not only for tracking rare or threatened species but also to detect the increase of potentially invasive species4, and the trends in the populations of common species, which in some regions are declining even more rapidly than are rare species2. The combination of citizen science and cutting-edge technologies has improved monitoring programmes.5 In this regard, camera traps have become a popular tool to engage with society while obtaining accurate scientific data.3 The importance of advances in technological monitoring has even been highlighted by the United Nations Environment Programme (UNEP) through the proposed ‘Digital Ecosystem framework’, a complex distributed network or interconnected socio-technological system.6 Monitoring species and ecosystems is critical to Africa – a highly biodiverse continent with numerous mammal species threatened by human activities such as poaching, overhunting, and climate and land-use change.7 Over half the terrestrial mammals in Africa have experienced range contractions of as much as 80% on average, including predator species such as lions (Panthera leo) and large ungulates.2 In sub-Saharan Africa, human impacts are projected to increase, and trigger an increased extinction risk.7 However, information on the conservation status of many species is limited, and many areas in Africa lack the baseline biodiversity data necessary to assess the outcomes of existing conservation programmes.5 Further, the lack of standardised methods to assess biodiversity patterns limits our ability to detect and respond to changes in mammal populations caused by environmental and anthropogenic factors.8 In attempting to address some of the above challenges, we have formed the Snapshot Safari Network (www. snapshotsafari.org) – a large-scale international camera trap network to study and monitor the diversity and ecological dynamics of southern and eastern African mammals. Snapshot Safari (hereafter Snapshot) is one of the largest camera trap networks in the world. It began in 2010 with a single camera trap grid in Serengeti National Park, Tanzania9, and the model and protocols have since been expanded in Tanzania as well as into five other countries: Botswana, Kenya, Mozambique, South Africa, and Zimbabwe (Figure 1). Participating locations represent a wide variety of habitats, wildlife communities, management types and protected area sizes. Here, we introduce this multidisciplinary initiative which combines citizen science and advanced machine learning techniques for the analysis of millions of animal photographs. We also introduce a set of high priority research questions emanating from expert consultation in 2019.
... Negative interactions have been the most studied, with predators not only competing through depletion of common prey but also posing threats to each other through kleptoparasitism (Höner et al. 2002;Trinkel and Kastberger 2005) and direct interference during aggressive interactions with risk of injury (Linnell and Strand 2000) and intraguild predation (Palomares and Caro 1999). These negative interactions can cause subordinate species to spatially and/ or temporally avoid dominant ones (Durant 2000;Vanak et al. 2013), similarly to the ecology of fear in predator-prey interactions (Courbin et al. 2013;Palmer et al. 2017;Kohl et al. 2019). However, this is not always the case, and evidence has accumulated on the absence of spatial and temporal avoidance between sympatric apex predators (Cozzi et al. 2012;Miller et al. 2018). ...
Article
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Apex predators play important roles in ecosystem functioning and, where they coexist, intraguild interactions can have profound effects on trophic relationships. Interactions between predators range from intraguild predation and competition to facilitation through scavenging opportunities. Despite the increased availability of fine-scale GPS data, the determinants and outcomes of encounters between apex predators remain understudied. We used simultaneous GPS data from collared spotted hyaenas (Crocuta crocuta) and African lions (Panthera leo) in Hwange National Park, Zimbabwe, to determine the environmental conditions of the encounters between the two species, which species provoked the encounter, and which species dominated the encounter. Our results show that encounters between hyaenas and lions are mostly resource-related (over a carcass or around waterholes). In the wet season, encounters mainly occur at a carcass, with lions being dominant over its access. In the dry season, encounters mainly occur in the absence of a carcass and near waterholes. Movements of hyaenas and lions before, during, and after these dry-season encounters suggest two interference scenarios: a passive interference scenario whereby both predators would be attracted to waterholes but lions would leave a waterhole used by hyaenas because of prey disturbance, and an active interference scenario whereby hyaenas would actively chase lions from waterhole areas, which are prime hunting grounds. This study highlights the seasonal dynamics of predator interactions and illustrates how the relative importance of negative interactions (interference competition during the dry season) and positive interactions (scavenging opportunities during the wet season) shifts over the course of the year.
... Natural cycles of lunar light intensity also affect the nocturnal activity patterns of mammals in a variety of complex ways (Colino-Rabanal et al., 2018;Palmer et al., 2017;Prugh and Golden, 2014). For example, the effects of moonlight on nocturnal predator activity can be shaped by the quality of their preferred hunting strategy (Carnevali et al., 2016). ...
Article
Natural cycles of light and darkness shift the balance of risks and gains for animals across space and time. Entrainment to photic cycles allows animals to spatiotemporally adapt their behavioural and physiological processes in line with interplaying ecological factors, such as temperature, foraging efficiency and predation risk. Until recently, our understanding of these chronobiological processes was limited by the difficulties of 24 hr observations. Technological advances in GPS biotelemetry however are now allowing us unprecedented access to long-term, fine-scale activity data. Here we use data derived from frontline technology to present the first large-scale investigation into the effects of natural fluctuations of light and darkness on the locomotor activity patterns of a threatened African mega-herbivore, the giraffe (Giraffa spp.). Using data from a remote population of Angolan giraffe (G. g. angolensis) in the northern Namib Desert, Namibia, we reveal the first full picture of giraffe chronobiology in a landscape of fear. Furthermore, we present clear evidence of the effect of moonlight on the nocturnal activity patterns of large ungulates. Our results are in line with recent research demonstrating that, rather than a fixed internal representation of time (circadian clock), many surface-dwelling ungulates have plastic activity patterns that are vulnerable to modification by external factors including light and temperature. Relatedly, we highlight important conservation management implications of rising temperatures and increasing light pollution on the chronobiology of surface-dwelling mammals.
... Temporal variation in cue availability arises from the activity patterns of predators (Palmer et al. 2017) and the persistence of cues (especially of odors) in the environment (Turner and Montgomery 2003). Some prey animals respond to temporal variation in predator cues by seeking shelter when the perceived risk of predation is high; meanwhile, prey take advantage of periods of relative safety to forage and be active (Lima and Bednekoff 1999). ...
Article
Full-text available
Abstract The threat‐sensitive predator avoidance hypothesis suggests that prey animals should minimize the costs of antipredator behaviors by only responding to predators that pose a potentially lethal threat. Thus, prey must use risk assessment strategies to determine which predators present a great enough threat to merit a response. A rich literature demonstrates that chemical signals can communicate information about predator identity, diet, and size. However, the relationship between predator size and prey size has been largely overlooked. What remains unknown is how prey respond to odors from predators along a continuum of relative size. Here, we tested the responses of crayfish (prey) to odor cues from two species of predatory fish along a gradient of relative size relationships. Crayfish and fish were paired according to crayfish carapace width and the fish’s gape width to represent different relative size pairings. Foraging and shelter use video assays were used to evaluate changes in crayfish behavior under the different levels of threat presented. The analysis revealed significant increases in macrophyte consumption, foraging effort, and overall activity among crayfish that were small relative to their predators, independent of the absolute size of fish or crayfish size. Crayfish that were small relative to predator size showed significantly less shelter use than crayfish that were large relative to predator gape size. The results demonstrate that the crayfish are assessing threat based on their size relative to the predator gape size solely using chemical signals. As a result of this assessment, crayfish are changing their resource use to potentially grow larger to limit future predatory threats. Overall, this research supports the threat‐sensitive predator avoidance hypothesis and provides an opportunity to refine the landscape of fear concept to accommodate more detailed risk assessments by prey.
... We hypothesize that these effects result in the lunar patterns of growth for larval sixbars. Influxes of both prey and predators may be relatively high during the new moon, and predation risk may prevent larval fish from capitalizing on increased prey biomass [75] (figure 4a). Predator and prey DVMs may both be suppressed during the full moon, leading larval fish to be relatively free of risk, but with relatively little food in the surface waters, resulting in no net growth advantage (figure 4c). ...
Article
Growth and survival of larval fishes is highly variable and unpredictable. Our limited understanding of this variation constrains our ability to forecast population dynamics and effectively manage fisheries. Here we show that daily growth rates of a coral reef fish (the sixbar wrasse, Thalassoma hardwicke ) are strongly lunar-periodic and predicted by the timing of nocturnal brightness: growth was maximized when the first half of the night was dark and the second half of the night was bright. Cloud cover that obscured moonlight facilitated a ‘natural experiment’, and confirmed the effect of moonlight on growth. We suggest that lunar-periodic growth may be attributable to light-mediated suppression of diel vertical migrations of predators and prey. Accounting for such effects will improve our capacity to predict the future dynamics of marine populations, especially in response to climate-driven changes in nocturnal cloud cover and intensification of artificial light, which could lead to population declines by reducing larval survival and growth.
... The perceived costs and benefits of particular environments can vary both spatially and temporally, especially in highly seasonal systems. For example, light conditions can alter predation risk (Palmer et al. 2017) and energetic costs of movement can increase with seasonal snow cover (Crête and Larivière 2003). Carnivores, particularly apex predators, have a fundamentally different relationship with their environment than other species because they are not directly reliant on vegetation to meet their energetic demands and, excluding human exploitation, Communicated by Mathew Samuel Crowther. ...
Article
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The dynamic environmental conditions in highly seasonal systems likely have a strong influence on how species use the landscape. Animals must balance seasonal and daily changes to landscape risk with the underlying resources provided by that landscape. One way to balance the seasonal and daily changes in the costs and benefits of a landscape is through behaviorally-explicit resource selection and temporal partitioning. Here, we test whether resource selection of coyotes (Canis latrans) in Cape Breton Highlands National Park, Nova Scotia, Canada is behaviorally-explicit and responsive to the daily and seasonal variation to presumed costs and benefits of moving on the landscape. We used GPS data and local convex hulls to estimate space use and Hidden Markov Models to estimate three types of movement behavior: encamped, foraging, and traveling. We then used integrated step-selection analysis to investigate behaviorally explicit resource selection across times of day (diurnal, crepuscular, and nocturnal) and season (snow-free and snow). We found that throughout the day and seasonally coyotes shifted foraging behavior and altered behavior and resource choices to avoid moving across what we could be a challenging landscape. These changes in behavior suggest that coyotes have a complex response to land cover, terrain, and linear corridors that are not only scale dependent but also vary by behavior, diel period, and season. By examining the resource selection across three axes (behavior, time of day, and season), we have a more nuanced understanding of how a predator balances the cost and benefits of a stochastic environment.
... The landscape of fear model predicts prey animals perceive and respond to spatial variation in predation risk and adjust their antipredator behaviors accordingly to minimize the risk of predation (Laundr e et al. 2001(Laundr e et al. , 2010. The landscape of fear experienced by individuals can be dynamic across multiple timescales, for instance due to changes in daily predator activity (Kohl et al. 2018) or shifting risk from lunar cycles (Palmer et al. 2017). Moreover, the landscape of fear for prey populations can be dynamic over generational timescales because of longer-term structural changes to habitats (Wheeler andHik 2014, Riginos 2015). ...
Article
Full-text available
Shrub encroachment is transforming arid and semiarid grasslands worldwide. Such transitions should influence predator-prey interactions because vegetation cover often affects risk perception by prey and contributes to their landscape of fear. We examined how the landscape of fear of two desert lago-morphs (black-tailed jackrabbit, Lepus californicus; desert cottontail, Sylvilagus audubonii) changes across grassland-to-shrubland gradients at Jornada Basin Long Term Ecological Research site in the Chihuahuan Desert of southern New Mexico. We test whether shrub encroachment shapes risk differently for these two lagomorphs because of differences in body size and predator escape tactics. We also examine whether an ecosystem engineer of grasslands (banner-tailed kangaroo rat, Dipodomys spectabilis) mediates risk perception through the creation of escape refuge and whether trade-offs exist between shrub encroachment and the local reduction of banner-tailed kangaroo rats caused by shrub expansion. We measured perceived pre-dation risk with flight initiation distances (FIDs) and then used structural equation modeling to tease apart the hypothesized direct and indirect pathways for how shrub encroachment could affect perceived risk. A total negative effect of shrub cover on FID was supported for jackrabbits and cottontails, suggesting both species perceive shrubbier habitat as safer. Increases in fine-scale concealment also reduced risk for cotton-tails, but not jackrabbits, likely because cottontails rely on crypsis to avoid predator detection whereas jackrabbits rely on speed and agility to outrun predators. Perceived risk was reduced when individuals were near kangaroo rat mounds only for cottontails because the smaller species can use banner-tailed kangaroo rat mounds as refuge. Shrub encroachment greatly reduced the availability of mounds. Thus, a trade-off exists for cottontails in which shrub encroachment directly reduced perceived risk, but indirectly increased perceived risk through the local extirpation of an ecosystem engineer. Our work illustrates how the expansion of shrub encroachment can create a dynamic landscape of fear for populations of prey species involving direct and indirect pathways contingent on prey body size, escape tactics, and activities of an ecosystem engineer.
... The apparent reluctance of the lake-tagged trout to move through transitional habitat around the full moon reflects previous observations of trout moving smaller distances during the full than the new moon (Slavik, Horky, Randak, Balvin, & Bíly, 2012;Slavik, Horky, Maciak, Horka, & Langrova, 2018). Analogous patterns of reduced activity or presence within exposed habitats during the full moon have been recorded in terrestrial rodents (Daly, Behrends, Wilson, & Jacobs, 1992;Kotler et al., 1991;Lockard & Owings, 1974), catadromous eels (Poole, Reynolds, & Moriarty, 1990;Sandlund et al., 2017), marine fishes (Hammerschlag et al., 2017), bats (Morrison, 1978), armadillos (Pratas-Santiago, Gonçalves, Nogueira, & Spironello, 2017), ungulates (Palmer, Fieberg, Swanson, Kosmala, & Packer, 2017) and zooplankton (Last et al., 2016). Such 'lunar phobia' is regarded as an evolved response that reduces exposure to visually oriented predators. ...
Article
Full-text available
Animals often exhibit extensive flexibility in movement behaviours on a range of temporal and spatial scales in response to cues that reliably predict fitness outcomes. The annual timing of movements between distinct habitats can be crucial, particularly in seasonal environments with narrow ecological windows of opportunity. In polygamous species, sexual selection may further shape sex-specific phenology and movement behaviours. Here, we characterized seasonal, daily and diel movement patterns in adult brown trout, Salmo trutta, between a lake feeding habitat and two spawning streams in northwestern Ireland, using passive integrated transponder (PIT) telemetry. Antennae positioned at the inflow and outflow of the lake were used to monitor movements of 197 lake-tagged adults between lake and stream habitats. Across 2 years in both streams, movements were overwhelmingly nocturnal and exhibited distinct seasonality, with a peak in daily detections close to the winter solstice. In both streams, seasonal movement activity of males began and peaked before that of females (protandry). Daily detection probabilities for both sexes increased as the moon waned (decreasing lunar illumination) and as river depth increased, the latter being associated with reduced water clarity. These findings are consistent with fish favouring movement between fluvial and lacustrine habitats when light (both solar and lunar) or hydrological conditions decrease their exposure to visually oriented predators. The observed protandry also suggests a role for intrasexual male competition, whereby earlier male arrival could increase mating opportunities.
... Chart relationships delineated with heavy lines represent instances where 4 representative CARTs agreed while relationships delineated with lighter lines represent instances where at least half but not all constituent CARTs agreed. See Section S, Figure S4 in supplementary materials (ESM 3) for detailed CARTs synthesized here Theor Ecol local primary productivity and prey for apex predators that deposit nutrient-rich carcasses along migration routes (e.g., lions, crocodiles) (Palmer et al. 2017;Subalusky et al. 2017). Socially cued wildebeest aggregation and migration therefore spread nutrient subsidy impacts like nutrient and vegetation hotspots from initial aggregation locations along migration routes. ...
Article
Full-text available
Animal sociality (i.e., conspecific attraction or avoidance) can influence how animals move (i.e., sinuous to straight) across landscapes. Active subsidies are animal-transported resources (e.g., nutrients, detritus, prey) or consumers (e.g., predators, parasites, pathogens) across ecosystem boundaries and can affect ecosystem function. Animal movement has been shown to affect the spatial distributions of active subsidies. However, there is limited research on how conspecific interaction affects active subsidy distributions through animal movement. Based on dispersal from a donor to recipient ecosystem, we constructed a spatially explicit individual-based model (IBM) to quantify the effect of variation in conspecific interaction in three scenarios (attraction, avoidance, no interaction) and movement behavior as a correlated random walk on living and dead subsidy displacement, density, and clustering. In each conspecific interaction scenario, we examined emergent subsidy distributions from varying the straightness of movement path and the settlement probability as a function of settled conspecifics within dispersers’ perceptual range. Movement behavior predicted subsidy displacement, and conspecific interaction determined subsidy density and clustering patterns. We found that avoidance spread subsidies farther and at lower densities in the recipient ecosystem, generating more spread-out dead subsidy clusters. Attraction resulted in fewer, smaller, and denser living subsidy clusters closer to the ecosystem boundary. Higher settlement probability constrained living subsidy displacement with increased subsidy density and clustering across conspecific interaction scenarios. Subsidy density and clustering increased with perceptual range in attraction scenarios, limiting subsidy displacement. Subsidy displacement increased with perceptual range in avoidance scenarios, reducing subsidy density and clustering. This work is the first systematic simulation study on the influence of animal movement interactions with sociality on spatial subsidies across a broad parameter space. Our work provides context for empirical studies of active subsidy distribution and impact for a variety of taxa and ecosystems.
... The landscape of fear is an established concept in predator-prey interaction studies [19][20][21] . It posits that animals learn about spatiotemporal variations in risk through predation escapes, and the learnt fear shapes their decisions over where and when to feed, travel and rest 22 . ...
Article
Full-text available
Human-wildlife coexistence is possible when animals can meet their ecological requirements while managing human-induced risks. Understanding how wildlife balance these trade-offs in anthropogenic environments is crucial to develop effective strategies to reduce risks of negative interactions, including bi-directional aggression and disease transmission. For the first time, we use a landscape of fear framework with Bayesian spatiotemporal modelling to investigate anthropogenic risk-mitigation and optimal foraging trade-offs in Critically Endangered western chimpanzees ( Pan troglodytes verus ). Using 12 months of camera trap data (21 camera traps, 6722 camera trap days) and phenology on wild and cultivated plant species collected at Caiquene–Cadique, Cantanhez National Park (Guinea-Bissau), we show that humans and chimpanzees broadly overlapped in their use of forest and anthropogenic parts of the habitat including villages and cultivated areas. The spatiotemporal model showed that chimpanzee use of space was predicted by the availability of naturalised oil-palm fruit. Chimpanzees used areas away from villages and agriculture more intensively, but optimised their foraging strategies by increasing their use of village areas with cultivated fruits when wild fruits were scarce. Our modelling approach generates fine-resolution space–time output maps, which can be scaled-up to identify human-wildlife interaction hotspots at the landscape level, informing coexistence strategy.
... Behavioural responses of animals to perceived risk are manifold; they vary between species, with intensity, spatial and temporal distribution and predictability of predation risk, and with the expected gain from foraging (Lima and Dill 1990, Houston and McNamara 1999, LaManna and Martin 2016. Moreover, animals can learn to adjust their behaviour in response to changing risks (DePasquale et al. 2014, Palmer et al. 2017, Aguilar-Argüello et al. 2019. ...
Article
Full-text available
One of the strongest determinants of behavioural variation is the tradeoff between resource gain and safety. Although classical theory predicts optimal foraging under risk, empirical studies report large unexplained variation in behaviour. Intrinsic individual differences in risk‐taking behaviour might contribute to this variation. By repeatedly exposing individuals of a small mesopredator to different experimental landscapes of risks and resources, we tested 1) whether individuals adjust their foraging behaviour according to predictions of the general tradeoff between energy gain and predation avoidance and 2) whether individuals differ consistently and predictably from each other in how they solve this tradeoff. Wild‐caught individuals (n = 42) of the jumping spider Marpissa muscosa, were subjected to repeated release and open‐field tests to quantify among‐individual variation in boldness and activity. Subsequently, individuals were tested in four foraging tests that differed in risk level (white/dark background colour) and risk variation (constant risk/variable risk simulated by bird dummy overflights) and contained inaccessible but visually perceivable food patches. When exposed to a white background, individuals reduced some aspects of movement and foraging intensity, suggesting that the degree of camouflage serves as a proxy of perceived risk in these predators. Short pulses of acute predation risk, simulated by bird overflights, had only small effects on aspects of foraging behaviour. Notably, a significant part of variation in foraging was due to among‐individual differences across risk landscapes that are linked to consistent individual variation in activity, forming a behavioural syndrome. Our results demonstrate the importance of among‐individual differences in behaviour of animals that forage under different levels of perceived risk. Since these differences likely affect food–web dynamics and have fitness consequences, future studies should explore the mechanisms that maintain the observed variation in natural populations.
... Information therefore affects organismal abundance and genetic composition in connected ecosystems across a landscape, and ultimately influences the transfer of materials and information among ecosystems (see Figure 3), which in turn may feed back to reinforce ecosystem heterogeneity (Monk et al. 2020). Light is a cue for development (Fankhauser & Chory 1997) and behavior (Karban 2008); visibility affects trophic interactions (Gliwicz 1986) and perceived risk thereof (Palmer et al. 2017 Animals use a variety of information sources to decide where to settle after migration, e.g. infochemicals (Dittman & Quinn 1996) or social information (Doligez 2002) In addition to abiotic information and structural cues, both conspecific (Greene & Stamps 2001) and heterospecific (Goodale et al. 2010) presence and performance can provide information about habitat quality (Parejo et al. 2005). ...
Preprint
Fluxes of matter, energy, and information over space and time contribute to ecosystems’ functioning. The meta-ecosystem framework addresses the dynamics of ecosystems linked by these fluxes, however, to date, meta-ecosystem research focused solely on fluxes of energy and matter, neglecting information. This is problematic due to organisms’ varied responses to information, which influence local ecosystem dynamics and can alter spatial flows of energy and matter. Furthermore, information itself can move between ecosystems. Therefore, information should contribute to meta-ecosystem dynamics, such as stability and productivity. Specific subdisciplines of ecology currently consider different types of information (e.g., social and cultural information, natural and artificial light or sound, body condition, genotype, and phenotype). Yet neither the spatiotemporal distribution of information nor its perception are currently accounted for in general ecological theories. Here, we provide a roadmap to synthesize information and meta-ecosystem ecology. We begin by defining information in a meta-ecological context. We then review and identify challenges to be addressed in developing information meta-ecology. Finally, we present new hypotheses for how information could impact dynamics across scales of spatio-temporal and biological organization.
... In this predator-prey game around waterholes with low vegetation cover, the moon phase may have had a particular influence [58]. Only the snow leopard and Eurasian lynx (the species with a greater degree of activity overlap) showed an activity pattern moderately influenced by the lunar phase, suggesting a potential influence on predator-prey behavioral decisions [54]. However, the lowest influence of the moon phase was found among the prey species (herbivores). ...
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Background Animal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics. Results Complex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species. Conclusions Altogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies.
... ;Kuijper et al., 2015; Gallager et al., 2017;Gaynor et al., 2019;Zanette and Clinchy, 2019). These factors fluctuate in time, as well as space, creating fluid, dynamic situations where localities can change quickly from being safe to dangerous, and vice-versa(Courbin et al., 2019;Kohl et al., 2018;Palmer et al., 2017;Smith et al., 2019;Swanson et al., 2016;Zeller et al., 2019). Birds often respond to increased interspecific aggression by decreasing frequency of visits and time spent ...
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Fear of humans and its effect on animal behavior is increasingly being recognized as an important structuring force in ecological landscapes, with consequences for ecological interactions and communities. When aggressive, physically dominant species are displaced by anthropogenic disturbance, physically weaker species exploit competitor and predator downtimes to forage in previously risky places. Birds feeding at outdoor restaurants and cafés in association with humans are exposed to fluctuating levels of perceived danger caused by frequently changing densities of human diners. Consequently, birds must make decisions about which dining tables to visit based on trade‐offs between foraging gain and perceived danger from avian competitors and humans. We tested the hypothesis that interspecific differences in response to perceived danger, combined with varying densities of human diners, dynamically alter which bird species predominates at dining tables. We found that house sparrows (Passer domesticus) tolerated higher human diner‐densities than larger‐sized, more physically dominant Eurasian jackdaws (Coloeus monedula). Sparrows were usually the first birds to visit diner‐occupied tables and spent more time there than jackdaws. However, at diner‐abandoned tables, this pattern changed: During low diner‐densities at surrounding tables, jackdaws were usually the predominant species in first visits and minutes spent visiting, while at high diner‐densities sparrows usually predominated. Moreover, along a gradient of increasing human diner‐density, sparrows gradually replaced jackdaws as the predominant species in first visits and time at abandoned tables. However, at diner‐occupied tables, once a sparrow chose which table to visit, factors other than diner‐density influenced its choice of where to forage there (table‐top or ground). To our knowledge, our research is the first scientific study of table‐visiting behavior by birds at outdoor restaurants and cafés, and the first to reveal interspecific differences in table‐visiting behavior by birds there. We tested the hypothesis that interspecific differences in response to perceived danger, combined with varying densities of human diners, dynamically alter which bird species predominates at dining tables. House sparrows (Passer domesticus) tolerated higher human diner‐densities than Eurasian jackdaws (Coloeus monedula). Sparrows were usually the first birds to visit diner‐occupied tables and spent more time there than jackdaws. However, at diner‐abandoned tables, this pattern changed: during low diner‐densities at surrounding tables, jackdaws were usually the predominant species in first visits and minutes spent visiting. However, along a gradient of increasing human diner‐density, sparrows gradually replaced jackdaws as the predominant species in first visits and time at abandoned tables.
... For example, in pronghorns (Antilocapra americana), Kitchen (1974) showed a positive correlation between forage quality in a territory and either the average number of females present or the mating success of males. With respect to top-down mechanisms, species can alter their habitat use in response to predation risk, avoid areas of high quality or quantity of forage to increase safety (Creel et al. 2005), change temporal and spatial patterns of habitat use (Valeix et al. 2009;Riginos 2015;Palmer et al. 2017), increase vigilance and reduce foraging time (Creel et al. 2014) and change group size (Makin et al. 2017). ...
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The factors that regulate the abundance and distribution of wild herbivores are key components of a species’ ecology and include bottom-up and top-down mechanisms, as well as aspects related to social organization. In territorial ungulates, males distribute themselves to enhance access to females by anticipating how resources will influence female distribution. Although the variables that influence the distribution of territorial males have implications for mating opportunities and reproductive success, these relationships remain largely unknown. We assessed how bottom-up, top-down and social factors influence the spatial distribution of territorial male guanacos (Lama guanicoe) in a semiarid ecosystem during three periods of the reproductive season, in a population with two alternative mating tactics: a resource-defence tactic adopted by family group males and a clustered territorial tactic adopted by solitary males. We conducted ground surveys of males from both social units and used density surface models to assess the influence of primary productivity, predation risk and female grouping on their spatial distribution. Our results showed that territorial males were more abundant in areas of increased primary productivity during the group formation period in years of good plant growth and higher number of females/female groups throughout the reproductive season, suggesting that both bottom-up and social traits regulate their spatial distribution. Predation risk did not significantly influence the abundance of territorial males. Overall, our research contributes to the understanding of territorial systems in ungulates and reinforces the current theory that bottom-up processes are relatively more important than top-down processes in regulating populations of large herbivores. Significance statement Many factors operate together to regulate the abundance and spatial distribution of territorial ungulates. Understanding these relationships has implications for mating opportunities and reproductive success. In this study, we combined field data with density surface models to assess the influence of bottom-up, top-down and social factors on the spatial distribution of a territorial ungulate during the reproductive season. We used the guanaco (Lama guanicoe), the main wild ungulate of the southern region of South America, as a study model. Our results suggest that in low-productivity environments, bottom-up (primary productivity) and social traits (female grouping) predominate in regulating the spatial distribution of territorial male guanacos, rather than top-down factors (predation risk). We highlight the possibility that different populations of herbivores respond differently depending on environmental conditions that shape both the quality and quantity of forage and predation.
... More generally, this modeling framework could be used to explore the evolution of specific growth patterns under different size-dependent predation pressures. For example, prey with gape-limited predators sometimes have rapid initial grow to escape predation (Urban 2007;Nowlin et al. 2006), rodents use moon light cues as a proxy for bird predation and stop foraging more on moon-lit nights (Palmer et al. 2017), copepods have daily movement up and down in the water column to decrease predation (Bollens and Stearns 1992), and younger, smaller prey respond more strongly to predators than older, less vulnerable conspecifics (Thaler and Griffin 2008). This modeling framework could be applied to consider how specific predation pressures might lead to the evolution of different prey growth patterns. ...
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Prey species make choices about whether to employ costly predator avoidance behaviors throughout their growth and lifecycle. Here, we explore the effects of prey size at a given age (ontogenetic size) and prey growth on optimal behavior using a dynamic optimization model. Under the assumption that prey experience greatest predation risk at intermediate or large sizes, and that growth is fastest at intermediate or large sizes, we find that prey should generally forage when they are small in size and hide when they are larger due to a critical strategy switching size threshold. But this is dependent both on the mortality risks and on the rate of growth. Higher background mortality rates or lower predator-induced detection costs of foraging reduce the size at which prey switches from foraging to hiding. Rapid initial growth leads to decreased overall survival and a wider range of conditions under which the prey hides from the predator. As a test case, the model is parametrized with data and applied to understand differing risk-reducing behaviors between cannibal and non-cannibal Leptinotarsa decemlineata, Colorado potato beetle, larvae. The model predicts that a wide range of parameter values lead to differing behaviors of cannibals and non-cannibals of the same age due to differences in ontogenetic size. We also see that individuals with swifter early growth switch to hiding at larger sizes but will often have earlier strategy switching times. This increases survival of cannibals to the critical pupation size with the largest increases occurring when the baseline death rate is high. Our findings suggest that ecological factors that affect the rate of growth during development, even if final size is not affected, may have an important role in prey responses to predators.
... An alternative or additional solution to shifting space use could be to alter activity patterns when activity of predators or competitors is highest or when hunting success of predators is maximized (Crawford et al., 2021;Gaynor, 2019;Kohl et al., 2018;Palmer et al., 2017;Smith et al., 2019). For instance, coursing predators who rely on visual cues are more likely to hunt during dawn and dusk, whereas ambush predators who rely on being undetected may hunt in darkness (Kohl et al., 2018(Kohl et al., , 2019Pierce et al., 2004). ...
Article
Understanding factors that influence animal behavior is central to ecology. Basic principles of animal ecology imply that individuals should seek to maximize survival and reproduction, which means carefully weighing risk against reward. Decisions become increasingly complex and constrained, however, when risk is spatiotemporally variable. We advance a growing body of work in predator‐prey behavior by evaluating novel questions where a prey species is confronted with multiple predators and a potential competitor. We tested how fine‐scale behavior of female mule deer (Odocoileus hemionus) during the reproductive season shifted depending upon spatial and temporal variation in risk from predators and a potential competitor. We expected female deer to avoid areas of high risk when movement activity of predators and a competitor were high. We used GPS data collected from 76 adult female mule deer, 35 adult female elk, 33 adult coyotes, and six adult mountain lions. Counter to our expectations, female deer exhibited selection for multiple risk factors, however, selection for risk was dampened by the exposure to risk within home ranges of female deer, producing a functional response in habitat selection. Furthermore, temporal variation in movement activity of predators and elk across the diel cycle did not result in a shift in movement activity by female deer. Instead, the average level of risk within their home range was the predominant factor modulating the response to risk by female deer. Our results counter prevailing hypotheses of how large herbivores navigate risky landscapes, and emphasize the importance of accounting for the local environment when identifying effects of risk on animal behavior. Moreover, our findings highlight additional behavioral mechanisms used by large herbivores to mitigate multiple sources of predation and potential competitive interactions.
... In terrestrial environments, prey are known to adjust their social and foraging behaviors across the lunar cycle to minimize visual detection by predators in the night (e.g. Daly et al. 1992;Kotler et al. 2010;Palmer et al. 2017). In addition, the frequency of visual displays to conspecific receivers increases on full moon nights in nocturnal birds (Penteriani et al. 2010;Alonso et al. 2021). ...
Article
Lunar phases might favor the maintenance of color polymorphism via disruptive selection if the different color variants performed differently in terms of prey capture under different moonlight levels. Moonlight, however, may affect prey capture as a side effect of its influence on prey behavior. Here we combine data of parental provisioning and quality of owlets with one ex-situ study of grasshopper activity to test whether Eurasian scops owls (Otus scops) with different plumage color and their prey are differently affected by moonlight. Food provisioning increased from new- to full-moon. However, the effect of moonlight on owlet mass gain and immune response depended on paternal coloration. On the one hand, body mass gain of nestlings of the greyest fathers increased from nights with new- to full-moon, whereas it did not change with moonlight for the brownest fathers. On the other hand, PHA response of nestlings of the brownest fathers increased with high moonlight levels during the first week of life, whereas it did not change with moonlight levels for the greyest fathers. Grasshoppers were more active at new moon than at full or waning moon. Our study provides supporting evidence that moonlight influences the behavior of both scops owls and its prey and suggests that fluctuations in environmental conditions can modulate the advantages of morphs. These results are important because they provide a general insight into a little appreciated mechanism for the maintenance of color polymorphism in natural populations based on the interactive effect of different environmental factors.
... Predation is a key selective force in the evolution of animal behaviour, shaping numerous behavioural adaptations relating to reproduction, sociality and foraging in a wide range of taxa (Schneider 1984;Lima and Dill 1990;Sih 1994;Khater et al. 2016). With respect to foraging, animals must weigh up the need to obtain food while minimising risks of predation, a decision-making process that is further complicated by the fact that predation pressure can vary spatially and temporally (Schartel and Schauber 2016;Palmer et al. 2017;Kohl et al. 2018). How individuals might balance this risk-reward trade-off, whereby they attempt to maximise their net energy intake, is explained in optimal foraging theory (OFT). ...
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Animals are faced with a fundamental risk-reward trade-off when making decisions about foraging in the presence of predation, yet little is known about how social, reproductive and environmental factors mediate this trade-off. In the marine environment, anemonefishes provide a model system for investigating the determinants of risk–reward trade-offs, because they live in size- and sex-structured groups within protective sea anemones tentacles, yet feed predominantly in the water column where they are at risk of predation. Furthermore, exposure to changing tides means the availability of planktonic food covaries with their risk of predation. Therefore, we examined how tide, sex and status, and the presence of eggs influenced the time that Amphiprion mccullochi spent at different distances from their anemone, a proxy for foraging effort and predation risk. We found that individuals significantly adjusted their time spent far and close to the anemone depending on the tide, status and the presence of eggs, and that these adjustments can be explained in light of threat sensitive behaviour. This study illustrates the relative importance of environmental and social factors on intraspecific variation in foraging and antipredator behaviour and bolsters our understanding of the decision’s individuals make to balance the costs and benefits of foraging over temporal and spatial scales.
... Risk-dependent responses of prey to perceived predation risk is indeed a well-studied phenomenon within predator-prey interactions (Miner et al. 2005;Stevens 2016). Given that the intensity of predation risk varies in time and space (Valeix et al. 2009;Palmer et al. 2017) and that antipredatory strategies come at a cost, the threat sensitivity hypothesis predicts that antipredator behavior is scaled in proportion to the magnitude of predation risk (Sih 1986;Helfman 1989). Thus, for animals capable of dynamically elaborating conspicuous mating signals, this hypothesis predicts that the extent of elaboration is inversely related to perceived predation risk from eavesdropping enemies. ...
Article
To thoroughly understand the drivers of dynamic signal elaboration requires assessing the direct and indirect effects of naturally interacting factors. Here, we use structural equation modeling to test multivariate data from in situ observations of sexual signal production against a model of causal processes hypothesized to drive signal elaboration. We assess direct and indirect effects, and relative impacts, of male-male competition and attacks by eavesdropping frog-biting midges (Diptera: Corethrellidae) on call elaboration of male túngara frogs (Engystomops pustulosus). We find that the intensity of attacks by these micropredator flies drives the extent to which frogs elaborate their calls, likely due to a temporal trade-off between signaling and antimicropredator defense. Micropredator attacks appear to dynamically limit a male's call rate and complexity and consequently dampen the effects of intrasexual competition. In accounting for naturally interacting drivers of signal elaboration, this study presents a counterpoint to the mechanisms traditionally thought to drive sexual selection in this system. Moreover, the results shed light on the relatively unexamined and potentially influential role of eavesdropping micropredators in the evolution of sexual communication systems.
... The "landscape of fear" concept, which describes the variation in perceived predation risk and its consequence for prey behavior and ecosystem functioning, is often applied as a framework in ecological studies Brown & Kotler, 2004;Gaynor et al., 2019). Predation risk varies spatially or temporally (Creel et al., 2008;Kohl et al., 2018;Palmer et al., 2017;Tolon et al., 2009), with prey typically facing a trade-off between risk avoidance and food acquisition (Brown & Kotler, 2004;Lima & Dill, 1990;McArthur et al., 2014). In the case of ungulate prey species, their response to their large carnivore predators may include changing their spatial use and activity patterns (Bonnot et al., 2020;Kuijper et al., 2015;Latombe et al., 2014;Lima & Dill, 1990;Valeix et al., 2009), increasing their vigilance and/or group size (Brown, 1999;Delm, 1990;Périquet et al., 2010) or changing the composition of their diet (Churski et al., 2021). ...
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The recolonization of human-dominated landscapes by large carnivores has been followed with considerable scientific interest; however, little is known about their interactive effect on ungulate foraging behavior. This study compared the risks imposed by humans and lynx on ungulate foraging behavior by examining the effects of browsing intensity (at two spatial scales), diet quality, and tree species selection. We hypothesized that: (1) in areas with high risk imposed by humans and lynx browsing intensity would be reduced; (2) risk effects would interact with habitat visibility at a fine scale, resulting in contrasting browsing patterns in response to humans versus lynx risk; (3) ungulates compensate for the higher costs incurred in high-risk areas by switching to a higher diet quality, and (4) browse a higher proportion of more-preferred tree species. These hypotheses were tested by measuring browsing intensity along 48 transects located at different distances from human settlements within the hunted and nonhunted areas of the Bavarian Forest. Dung samples were collected and analyzed as a proxy of diet quality (C:N ratio, fiber). The spatial patterns of browsing intensity, diet quality, and tree species selection were then linked to lynx risk, hunting intensity, recreation intensity, and distance to human settlements. Our results showed that (1) browsing intensity strongly decreased with increasing recreational activities, whereas it increased with lynx risk; (2) only in close proximity to human settlements tree browsing was higher in dense habitats and (3) a higher diet quality was obtained. (4) We found a stronger avoidance of the less preferred tree species in high-hunting intensity areas. In conclusion, our results indicate that the risk effects of human activities outweigh those of a natural large carnivore. Thus, highlighting the importance of taking those activities into account in predicting the impacts of large carnivores on ungulates and their plant-food choices.
... As a complementary approach to understanding the effects of individual variation on model performance, future efforts should test how habitat diversity and heterogeneity affect model performance. Many habitat selection models make the reasonable assumption that the most important habitats are where individuals are currently best adapted (Hebblewhite and Merrill 2009;Dupke et al. 2017;Palmer et al. 2017). But population-level habitat selection is adaptive either when different individuals select the habitats to which they are adapted, or the environment changes to suit their adaptations (Edelaar and Bolnick 2019). ...
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Predicting future space use by animals requires models that consider both habitat availability and individual differences in habitat selection. The functional response in habitat selection posits animals adjust their habitat selection to availability, but population-level responses to availability may differ from individual responses. Generalized functional response (GFR) models account for functional responses by including fixed effect interactions between habitat availability and selection. Population-level resource selection functions instead account for individual selection responses to availability with random effects. We compared predictive performance of both approaches using a functional response in elk (Cervus canadensis) selection for mixed forest in response to road proximity, and avoidance of roads in response to mixed forest availability. We also investigated how performance changed when individuals responded differently to availability from the rest of the population. Individual variation in road avoidance decreased performance of both models (random effects: β = 0.69, 95% CI 0.47, 0.91; GFR: β = 0.38, 95% CI 0.05, 0.71). Changes in individual road and forest availability affected performance of neither model, suggesting individual responses to availability different from the functional response mediated performance. We also found that overall, both models performed similarly for predicting mixed forest selection (F1, 58 = 0.14, p = 0.71) and road avoidance (F1, 58 = 0.28, p = 0.60). GFR estimates were slightly better, but its larger number of covariates produced greater variance than the random effects model. Given this bias-variance trade-off, we conclude that neither model performs better for future space use predictions.
... As a consequence, understanding the behavioral landscape can provide insights into underlying population variation related to predation risk and foraging opportunities, which may subsequently inform management of the system through approaches such as predator control or regulating human disturbance (Dwinnell et al. 2019). SRS plays a critical role in delineating spatial and temporal variation in forage resources, and SW images can be mined to generate behavioral data that are not otherwise available over relevant spatiotemporal scales, with the caveat that the interpretation of still images that are increasingly being used for behavioral analysis (e.g., Palmer et al. 2017) may be imperfect (Appendix S5). Analysis of deer foraging and vigilance behavior derived using crowdsourced classification of SW images (ignoring any proxies for predation risk), and results suggest that deer spend relatively less time foraging in areas with greater land cover diversity and greater remotely sensed plant productivity using annually integrated MODIS enhanced vegetation index as a proxy for annual productivity (Appendix S5). ...
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Biological data collection is entering a new era. Community science, satellite remote sensing (SRS), and local forms of remote sensing (e.g., camera traps and acoustic recordings), have enabled biological data to be collected at unprecedented spatial and temporal scales and resolution. There is growing interest in developing observation networks to collect and synthesize data to improve broad‐scale ecological monitoring, but no examples of such networks have emerged to inform decision‐making by agencies. Here, we present the implementation of one such jurisdictional observation network (JON), Snapshot Wisconsin, which links synoptic environmental data derived from SRS to biodiversity observations collected continuously from a trail camera network to support management decision‐making. We use several examples to illustrate that Snapshot Wisconsin improves the spatial, temporal, and biological resolution and extent of information available to support management, filling gaps associated with traditional monitoring and enabling consideration of new management strategies. JONs like Snapshot Wisconsin further strengthen monitoring inference by contributing novel lines of evidence useful for corroboration or integration. SRS provides environmental context that facilitates inference, prediction, and forecasting, and ultimately helps managers formulate, test, and refine conceptual models for the monitored systems. Although these approaches pose challenges, Snapshot Wisconsin demonstrates that expansive observation networks can be tractably managed by agencies to support decision making, providing a powerful new tool for agencies to better achieve their missions and reshape the nature of environmental decision‐making.
... Burkina Faso hunting concessions have among the highest levels of lion offtake per area in Africa (~15 lions killed per year) compared to exceptionally low offtake or lack of lion hunting altogether in the rest of the region (1-1. 5 ...
Thesis
African lions reside primarily in protected areas, both of which are increasingly threatened by human pressures and subsequent depletion of natural resources and suitable habitat. Management of protected areas as hunting concessions often results in higher revenues and smaller areas compared to national parks, allowing for high quality habitat and stronger regulation of illegal activity. The successful conservation of lions in protected areas where both management types are implemented could depend on the extent to which lions avoid the risks associated with human encounters, which likely depends on distribution of high-quality habitat, water availability and prey resources. We conducted the first camera survey of lions in the W-Arly-Pendjari (WAP) protected area in West Africa, a 26,620-km2 complex which has two primary management types: national parks (NPs) and hunting concessions (HCs). We combined occupancy modeling, which accounts for imperfect detection of lions, and structural equation modeling to disentangle the relative effect sizes (ES) of environmental, ecological, and anthropogenic variables expected to influence lion space use. Lion occupancy (𝜓) did not show a response to management type (𝜓NP = 0.56; 𝜓HC = 0.58), exhibiting no spatial avoidance of hunting concessions. Water availability was higher and habitats were more diverse in hunting concessions, which may negate mortality risks from trophy hunting and higher human occupancy (𝜓NP = 0.49; 𝜓HC = 0.61). Lion occupancy was strongly driven by prey availability (ES = 0.219), which was influenced by edge effects and water availability. Cues of highquality habitat combined with increased human pressures may indicate hunting concessions functioning as ecological traps for lions in WAP. We recommend management interventions (e.g., increasing water availability and patrols near park edges) to provide refuge for lions in national parks by reducing the intersection of lion space use and the risk of human encounters.
... For example, predominantly diurnal warthogs ran from the predator playbacks ( Fig. 2A) while predominantly nocturnal bushbuck, which commonly freeze when they perceive predators 34 , significantly increased their vigilance rather than running (Fig. 2B). Moreover, our results confirm that a better understanding of diel variation in activity may be necessary as it likely plays an important role in mediating the influence of vegetation on large carnivore-ungulate interactions 58,59 . ...
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The fear large carnivores inspire in large ungulates has been argued to have cascading effects down food webs. However, a direct link between ungulate habitat use and their fear of large carnivores has not been experimentally tested. To fill this critical gap, we conducted a bi-factorial experiment in an African savanna. We removed shrub cover and broadcast large carnivore vocalizations (leopard, hyena, dog) or non-threatening control vocalizations in both experimentally cleared and shrubby control sites. We recorded the proactive (frequency of visitation) and reactive (fleeing or vigilance) responses of multiple prey (impala, warthog, nyala and bushbuck). Critically, we found a significant proactive–reactive interaction. Ungulates were 47% more likely to run after hearing a predator vocalization in shrubby control sites than experimental clearings, demonstrating that ungulates perceived less fear from large carnivores in open habitat (clearings). Consistent with this finding, ungulates visited clearings 2.4 times more often than shrubby control sites and visited shrubby control sites less often at night, when large carnivores are most active. Combined with results from previous experiments demonstrating that the disproportionate use of available habitats by large ungulates can alter ecosystem properties, our experiment provides critical evidence that the fear large carnivores inspire in large ungulates can cause trophic cascades.
... which has operated continuously since 2010, is a flagship example of a long-term camera trap monitoring program. Over the last decade, this survey has gathered unprecedented longitudinal data that have significantly enhanced our understanding of the seasonal and inter-annual dynamics of the Serengeti ecosystem [37,3,27]. Projects of this magnitude have become increasingly common across eastern and southern Africa [35] and around the world [36]. ...
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Camera trapping is increasingly used to monitor wildlife, but this technology typically requires extensive data annotation. Recently, deep learning has significantly advanced automatic wildlife recognition. However, current methods are hampered by a dependence on large static data sets when wildlife data is intrinsically dynamic and involves long-tailed distributions. These two drawbacks can be overcome through a hybrid combination of machine learning and humans in the loop. Our proposed iterative human and automated identification approach is capable of learning from wildlife imagery data with a long-tailed distribution. Additionally, it includes self-updating learning that facilitates capturing the community dynamics of rapidly changing natural systems. Extensive experiments show that our approach can achieve a ~90% accuracy employing only ~20% of the human annotations of existing approaches. Our synergistic collaboration of humans and machines transforms deep learning from a relatively inefficient post-annotation tool to a collaborative on-going annotation tool that vastly relieves the burden of human annotation and enables efficient and constant model updates.
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Top predators largely affect ecosystems through trophic interactions, but they also can have indirect effects by altering nutrient dynamics and acting as ecosystem engineers. Arctic foxes ( Vulpes lagopus ) are ecosystem engineers that concentrate nutrients around their dens, creating biogeochemical hotspots with lush vegetation on the nutrient-limited tundra. Red foxes ( V. vulpes ) similarly engineer subarctic environments through their denning behavior, and have recently expanded onto the tundra where they now often occupy historically Arctic fox dens. We evaluated the impact of Arctic and red fox denning behavior on other tundra wildlife by comparing predator and herbivore visits to dens and adjacent control areas using camera traps in northeastern Manitoba, where both fox species are sympatric. Both the capture rates and species richness of wildlife were significantly greater at fox dens relative to control sites. Predators were detected almost exclusively on dens occupied by foxes, suggesting carcass or fox presence attracts predators to den sites. This is supported by observations of predators investigating and scavenging prey remains (carrion, feathers) from the dens. Caribou ( Rangifer tarandus ) visited dens more often than control areas, and we hypothesize they are attracted to the enhanced vegetation typically found on dens. Our results suggest Arctic fox ecosystem engineering has a prolonged, indirect effect on caribou by enriching vegetation at dens, whereas both Arctic and red foxes directly facilitate predators by provisioning resources. Understanding how predators affect other organisms via non-trophic interactions provides an enriched view of their functional roles within ecosystems.
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Individual foraging is under strong natural selection. Yet, whether individuals differ consistently in their foraging success across environments, and which individual and population-level traits might drive such differences, is largely unknown. We addressed this question in a field experiment, conducting over 1,100 foraging trials with nine subpopulations of guppies, Poecilia reticulata , translocating them across environments in the wild. A-priori, we determined the individual social phenotypes. We show that individuals consistently differed in reaching food, but not control, patches across environments. Social individuals reached more food patches than less social ones and males reached more food patches than females. Overall, individuals were, however, more likely to join females at patches than males, which explains why individuals in subpopulations with relatively more females reached, on average, more food patches. Our results provide rare evidence for individual differences in foraging success across environments, driven by individual and population level (sex ratio) traits.
Article
The landscape of fear (LOF) hypothesis is a unifying idea explaining the effects of predators on the space use of their prey. However, empirical evidence for this hypothesis is mixed. Recent work suggests that the LOF is dynamic, depending on the daily activity of predators, which allows prey to utilize risky places during predator down times. While this notion clarifies some discrepancies between predictions and observations, support for a dynamic LOF remains mixed. The underlying assumption of a dynamic LOF is strong predictability in predator activity cycles. Work in multi‐predator systems demonstrates the effect of differential behavior between predator species on the predictions of prey space use. However, none have considered the effect of intraspecific variation in predator behavior. Most, if not all, dynamic LOF studies base inference on the species‐level average activity pattern, implicitly assuming similarity within the predator population. We examined the dynamics and intraspecific variation in activity cycles within a population of coyotes (Canis latrans). We found seasonality in the predictability of coyote behavior, as well as divergent nocturnal and crepuscular activity patterns between individuals during summer. Activity dynamics were not related to range size, sex, body mass, or habitat complexity, but did vary by year. These results suggest that the predictability of activity patterns is seasonally dynamic, and failure to account for intraspecific variation in activity may cloud inference in LOF studies. We argue that future studies should not neglect the potential complexity of predator behavior with simplistic assumptions. By considering intraspecific variation in activity patterns, we may gain a clear picture of LOF dynamics.
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Prey species must often face a trade‐off between acquiring resources and minimizing predation risk. The spatial variation in predation risk across a landscape, as perceived by prey across their foraging or home range, creates a “landscape of fear” by which individuals modify their behavior in response to the level of perceived risk. Here, we explored the influence of perceived predation risk, habitat features associated with risk, and fruit availability, on the spatial variation in behavior of the endangered forest‐dwelling samango monkey (Cercopithecus albogularis schwarzi). We collected behavioral and location data on two habituated samango monkey groups in the Soutpansberg Mountains, South Africa, between 2012 and 2016. We further collected location data of the samango monkey's acoustically distinct alarm call, which has an unambiguous association with aerial predators, to spatially map perceived risk across the landscape. Using generalized linear mixed models, we found that perceived risk from eagles significantly influenced the spatial distribution of critical life‐functioning behaviors, with samango monkeys increasing feeding and foraging in high‐risk areas. To mitigate this risk, samangos increased cohesion between group members, which subsequently reduced vigilance levels. Group cohesion further increased in high‐risk areas with abundant fruit, relative to high‐risk, fruit‐poor areas, demonstrating the monkey's foraging/risk trade‐off. Feeding was also reduced in areas of low canopy height, while vigilance decreased with increasing understory visibility and distance from sleep site, showing the influence of landscape features on risk perception from other predator guilds. Thus, for arboreal species foraging in a 3‐D landscape, risk perception may occur at multiple scales and in response to multiple predator guilds. Only moving was influenced by fruit availability, either due to moving between localized food patches or from escaping high‐risk areas following feeding bouts. These findings highlight that risk‐taking in samango monkeys is only associated with behaviors fundamental to survival at a given location and that increased cohesion between neighbors is the main antipredator response in this species.
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Fluxes of matter, energy and information over space and time contribute to ecosystems' functioning and stability. The meta‐ecosystem framework addresses the dynamics of ecosystems linked by these fluxes but, to date, has focused solely on energy and matter. Here, we synthesize existing knowledge of information's effects on local and connected ecosystems and demonstrate how new hypotheses emerge from the integration of ecological information into meta‐ecosystem theory. We begin by defining information and reviewing how it flows among ecosystems to affect connectivity, local ecosystem function and meta‐ecosystem dynamics. We focus on the role of semiotic information: that which can reduce an individual's – or a group's – uncertainty about the state of the world. Semiotic information elicits behavioral, developmental and life history responses from organisms, potentially leading to fitness consequences. Organisms' responses to information can ripple through trophic interactions to influence ecosystem processes, their local and regional dynamics, and the spatiotemporal flows of energy and matter, therefore information should affect meta‐ecosystem dynamics such as stability and productivity. While specific subdisciplines of ecology currently consider different types of information (e.g. social and cultural information, natural and artificial light or sound, body condition, genotype and phenotype), many ecological models currently account for neither the spatio–temporal distribution of information nor its perception by organisms. We identify the empirical, theoretical and philosophical challenges in developing a robust information meta‐ecology and offer ways to overcome them. Finally, we present new hypotheses for how accounting for realistic information perception and responses by organisms could impact processes such as home range formation and spatial insurance, and thus our understanding of ecological dynamics across spatial and temporal scales. Accounting for information will be essential to understanding how dynamics such as fitness, organismal movement and trophic interactions influence meta‐ecosystem functioning, and predicting how ecosystem processes are affected by anthropogenic pressures.
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This chapter explores the primitive origins of fear in nature and its power to transform and influence ecosystems and human behavior. There are implications for understanding racism and its impact on human ecosystems and behavior.
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The temporal windows during which animals complete essential life processes (i.e. temporal niche) allow animals to match their actions to a given environmental context. When completing seasonal migrations, some migrants switch their activity patterns (e.g. from diurnal to nocturnal in multiple species of migratory birds) to take advantage of better conditions. We tested the temporal niche-switch hypothesis by comparing activity patterns before and during migration for four populations of migratory mule deer, Odocoileus hemionus, in western Wyoming, U.S.A. (2007–2019). We predicted that the physically taxing and risky event of terrestrial migration would prompt shifts in diel activity patterns. In contrast to the niche-switch hypothesis, mule deer did not drastically change their activity patterns during migration. Both before and during migration, mule deer were crepuscular (i.e. most active during twilight hours). When migrating in the spring, however, mule deer tended to concentrate activity near dawn, although they did not concentrate activity near dawn in the autumn, when less snow was present. By moving in the morning during spring migration, mule deer moved when snow was hardest, potentially allowing them to avoid the energetic costs of sinking into deep snow. Mule deer overall maintained a consistent pattern of crepuscular activity, but fine-tuned their activity patterns during migration, which may allow them to better match their behaviours with environmental conditions while completing an important life event. Rather than abandoning activity patterns, animals instead may make subtle alterations in their activity patterns to take advantage of present conditions.
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Most species adjust their behavior to reduce the likelihood of predation. Many experiments have shown that antipredator responses carry energetic costs that can affect growth, survival and reproduction, so that the total cost of predation depends on a trade-off between direct predation and risk effects. Despite these patterns, few field studies have examined the relationship between direct predation and the strength of antipredator responses, particularly for complete guilds of predators and prey. We used scan sampling in 344 observation periods over a four-year field study to examine behavioral responses to the immediate presence of predators for a complete antelope guild (dominated by wildebeest, zebra and oribi) in Liuwa Plains National Park, testing for differences in response to all large carnivores in the ecosystem (lions, spotted hyenas, cheetahs and African wild dogs). We quantified the proportion that each prey species contributed to the kills made by each predator (516 total kills), used distance sampling on systematic line transects to determine the abundance of each prey species, and combined these data to quantify the per-capita risk of direct predation for each predator-prey pair. On average, antelopes increased their vigilance by a factor of 2.4 when predators were present. Vigilance varied strongly among prey species, but weakly in response to different predators. Increased vigilance was correlated with reduced foraging in a similar manner for all prey species. The strength of antipredator response was not detectably related to patterns of direct predation (N = 15 predator-prey combinations with sufficient data). This lack of correlation has implications for our understanding of the role of risk effects as part of the limiting effect of predators on prey. This article is protected by copyright. All rights reserved.
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Herbivores play an important role in determining the structure and function of tropical savannahs. Here, we (i) outline a framework for how interactions among large mammalian herbivores, carnivores and environmental variation influence herbivore habitat occupancy in tropical savannahs. We then (ii) use a Bayesian hierarchical model to analyse camera trap data to quantify spatial patterns of habitat occupancy for lions and eight common ungulates of varying body size across an approximately 1100 km ² landscape in the Serengeti ecosystem. Our results reveal strong positive associations among herbivores at the scale of the entire landscape. Lions were positively associated with migratory ungulates but negatively associated with residents. Herbivore habitat occupancy differed with body size and migratory strategy: large-bodied migrants, at less risk of predation and able to tolerate lower quality food, were associated with high NDVI, while smaller residents, constrained to higher quality forage, avoided these areas. Small herbivores were strongly associated with fires, likely due to the subsequent high-quality regrowth, while larger herbivores avoided burned areas. Body mass was strongly related to herbivore habitat use, with larger species more strongly associated with riverine and woodlands than smaller species. Large-bodied migrants displayed diffuse habitat occupancy, whereas smaller species demonstrated fine-scale occupancy reflecting use of smaller patches of high-quality habitat. Our results demonstrate the emergence of strong positive spatial associations among a diverse group of savannah herbivores, while highlighting species-specific habitat selection strongly determined by herbivore body size. This article is part of the themed issue ‘Tropical grassy biomes: linking ecology, human use and conservation’.
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Moon phase affects nocturnal activity patterns in mammals. Among ungulates, a number of studies have found animals to be more active over full moon nights. This may be because increased luminosity provides increased opportunity to forage and/or increased ability to detect predators; known as the visual acuity hypothesis. Here, we use GPS-derived movement data to test for the influence of moon phase on plains zebra Equus quagga and blue wildebeest Connochaetes taurinus activity in Kruger National Park, South Africa. We compare animal movement (rate and displacement) over full and new moon nights, and consider the effect of lion proximity. We found that lion proximity largely determined the nocturnal movements of zebra and wildebeest, not moon phase. When lions were >1 km away, there was no difference in the nocturnal movement activity of prey animals over full and new moon conditions, contradicting previous findings. When lions were within 1 km of these animals, however, the movement of zebra and wildebeest greatly increased over the new moon, the relatively dark period when lion were most likely hunting. Although we could not explicitly test for predator detection here, our findings suggest that the visual acuity hypothesis does not hold for zebra and wildebeest in Kruger National Park (KNP) given that there is no evidence for increased foraging activity over the full moon. The influence of moon phase on the nocturnal activity of African ungulates may be more complicated than anticipated, and we suggest that this cannot be estimated unless predator proximity is accounted for.
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Citizen science has the potential to expand the scope and scale of research in ecology and conservation, but many professional researchers remain skeptical of data produced by nonexperts. We devised an approach for producing accurate, reliable data from untrained, nonexpert volunteers. On the citizen science website www.snapshotserengeti.org, more than 28,000 volunteers classified 1.51 million images taken in a large-scale camera-trap survey in Serengeti National Park, Tanzania. Each image was circulated to, on average, 27 volunteers, and their classifications were aggregated using a simple plurality algorithm. We validated the aggregated answers against a data set of 3829 images verified by experts and calculated 3 certainty metrics-level of agreement among classifications (evenness), fraction of classifications supporting the aggregated answer (fraction support), and fraction of classifiers who reported "nothing here" for an image that was ultimately classified as containing an animal (fraction blank)-to measure confidence that an aggregated answer was correct. Overall, aggregated volunteer answers agreed with the expert-verified data on 98% of images, but accuracy differed by species commonness such that rare species had higher rates of false positives and false negatives. Easily calculated analysis of variance and post-hoc Tukey tests indicated that the certainty metrics were significant indicators of whether each image was correctly classified or classifiable. Thus, the certainty metrics can be used to identify images for expert review. Bootstrapping analyses further indicated that 90% of images were correctly classified with just 5 volunteers per image. Species classifications based on the plurality vote of multiple citizen scientists can provide a reliable foundation for large-scale monitoring of African wildlife.
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The predator-prey space game and the costs associated with risk effects are affected by prey 1) proactive adjustments (when prey modify their behaviour in response to an a priori assessment of the risk level) and 2) reactive adjustments (when prey have detected an immediate threat). Proactive adjustments are generally well-studied, whereas the frequency, strength and duration of reactive adjustments remain largely unknown. We studied the space use and habitat selection of GPS-collared zebras Equus quagga from 2 to 48 h after an encounter with lions Panthera leo. Lion-zebra encounters generally occurred close to artificial waterholes (< 1 km). Two hours after an encounter, zebras were more likely to have fled than stay when the encounter occurred in more risky bushy areas. During their flight, zebras selected grasslands more than usual, getting great visibility. Regardless of their initial response, zebras finally fled at the end of the night and reached areas located far from waterholes where encounters with lions are less frequent. The large-scale flights (∼4-5 km) of zebras led to a local zebra depression for lions. Zebras that had fled immediately after the encounter resumed their behaviour of coming close to waterholes on the following day. However, zebras that had initially stayed remained far from waterholes for an extra 24 h, remaining an elusive prey for longer. The delay in the flight decision had different short-term consequences on the lion-zebra game. We reveal that the spatial context of the encounter shapes the immediate response of prey, and that encountering predators induces strong behavioural responses: prey flee towards distant, safer, areas and have a constrained use of key resource areas which are at the heart of the predator-prey game at larger spatio-temporal scales. Nighttime encounters were infrequent (once every 35 days on average), zebra responses were short-lived (< 36 h) but occurred over a large spatial scale (several km).
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Camera traps can be used to address large-scale questions in community ecology by providing systematic data on an array of wide-ranging species. We deployed 225 camera traps across 1,125 km(2) in Serengeti National Park, Tanzania, to evaluate spatial and temporal inter-species dynamics. The cameras have operated continuously since 2010 and had accumulated 99,241 camera-trap days and produced 1.2 million sets of pictures by 2013. Members of the general public classified the images via the citizen-science website www.snapshotserengeti.org. Multiple users viewed each image and recorded the species, number of individuals, associated behaviours, and presence of young. Over 28,000 registered users contributed 10.8 million classifications. We applied a simple algorithm to aggregate these individual classifications into a final 'consensus' dataset, yielding a final classification for each image and a measure of agreement among individual answers. The consensus classifications and raw imagery provide an unparalleled opportunity to investigate multi-species dynamics in an intact ecosystem and a valuable resource for machine-learning and computer-vision research.
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Ecological theory predicts that the intensity of antipredator responses is dependent upon the spatiotemporal context of predation risk (the risk allocation hypothesis). However, most studies to date have been conducted over small spatial extents, and did not fully take into account gradual responses to predator proximity. We simultaneously collected spatially explicit data on predator and prey to investigate acute responses of a threatened forest ungulate, the boreal caribou (Rangifer tarandus), to the spatiotemporal dynamics of wolf (Canis lupus) distribution during spring. Movement analysis of GPS-collared individuals from both species revealed high plasticity in habitat-selection decisions of caribou. Female caribou avoided open areas and deciduous forests and moved relatively fast and toward foraging areas when wolves were closer than 2.5 km. Caribou also avoided food-rich areas only when wolves were within 1 km. Our results bridge the gap between long-term perceived risk and immediate flight responses by revealing dynamic antipredator tactics in response to predator proximity.
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Predators alter prey dynamics by direct killing and through the costs of antipredator responses or risk effects. Antipredator behavior includes proactive responses to long-term variation in risk (e.g., grouping patterns) and reactive responses to short-term variation in risk (e.g., intense vigilance). In a 3-year field study, we measured variation in antipredator responses and the foraging costs of these responses for 5 ungulates (zebra, wildebeest, Grant’s gazelle, impala, and giraffe) that comprised more than 90% of the prey community available to the 2 locally dominant predators, lions and spotted hyenas. Using a model-selection approach, we examined how vigilance and group size responded to attributes of the predator, prey, and environment. We found that 1) the strength of antipredator responses was affected by attributes of the predator, prey, and environment in which they met; 2) grouping and vigilance were complementary responses; 3) grouping was a proactive response to the use of dangerous habitats, whereas vigilance was a reactive response to finer cues about predation risk; 4) increased vigilance caused a large reduction in foraging for some species (but not all); and 5) there was no clear relationship between direct predation rates and the foraging costs of antipredator responses. Broadly, our results show that antipredator responses and their costs vary in a complex manner among prey species, the predators they face, and the environment in which they meet.
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Maximum likelihood or restricted maximum likelihood (REML) estimates of the parameters in linear mixed-effects models can be determined using the lmer function in the lme4 package for R. As for most model-fitting functions in R, the model is described in an lmer call by a formula, in this case including both fixed- and random-effects terms. The formula and data together determine a numerical representation of the model from which the profiled deviance or the profiled REML criterion can be evaluated as a function of some of the model parameters. The appropriate criterion is optimized, using one of the constrained optimization functions in R, to provide the parameter estimates. We describe the structure of the model, the steps in evaluating the profiled deviance or REML criterion, and the structure of classes or types that represents such a model. Sufficient detail is included to allow specialization of these structures by users who wish to write functions to fit specialized linear mixed models, such as models incorporating pedigrees or smoothing splines, that are not easily expressible in the formula language used by lmer.
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Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. The importance of predation during evolutionary time is clear, but growing evidence suggests that animals also have the ability to assess and behaviorally influence their risk of being preyed upon in ecological time (i.e., during their lifetime). We develop an abstraction of the predation process in which several components of predation risk are identified. A review of the literature indicates that an animal's ability to assess and behaviorally control one or more of these components strongly influences decision making in feeding animals, as well as in animals deciding when and how to escape predators, when and how to be social, or even, for fishes, when and how to breathe air. This review also reveals that such decision making reflects apparent trade-offs between the risk of predation and the benefits to be gained from engaging in a given activity. Despite this body of evidence, several areas in the study of animal behavior have received little or no attention from a predation perspective. We identify several such areas, the most important of which is that dealing with animal reproduction. Much work also remains regarding the precise nature of the risk of predation and how it is actually perceived by animals, and the extent to which they can behaviorally control their risk of predation. Mathematical models will likely play a major role in future work, and we suggest that modelers strive to consider the potential complexity in behavioral responses to predation risk. Overall, since virtually every animal is potential prey for others, research that seriously considers the influence of predation risk will provide significant insight into the nature of animal behavior.
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Most studies in chronobiology focus on solar cycles (daily and annual). Moonlight and the lunar cycle received considerably less attention by chronobiologists. An exception are rhythms in intertidal species. Terrestrial ecologists long ago acknowledged the effects of moonlight on predation success, and consequently on predation risk, foraging behaviour and habitat use, while marine biologists have focused more on the behaviour and mainly on reproduction synchronization with relation to the Moon phase. Lately, several studies in different animal taxa addressed the role of moonlight in determining activity and studied the underlying mechanisms. In this paper, we review the ecological and behavioural evidence showing the effect of moonlight on activity, discuss the adaptive value of these changes, and describe possible mechanisms underlying this effect. We will also refer to other sources of night-time light ('light pollution') and highlight open questions that demand further studies.
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The elk or wapiti (Cervus elaphus) and bison (Bison bison) of Yellowstone National Park have lived in an environment free of wolves (Canis lupus) for the last 50 years. In the winter of 1994-1995, wolves were reintroduced into parts of Yellowstone National Park. Foraging theory predicts that elk and bison would respond to this threat by in - creasing their vigilance levels. We tested this prediction by comparing vigilance levels of elk and bison in areas with wolves with those of elk still in "wolf-free" zones of the Park. Male elk and bison showed no response to the reintro- duction of wolves, maintaining the lowest levels of vigilance throughout the study (≈12 and 7% of the time was spent vigilant, respectively). Female elk and bison showed significantly higher vigilance levels in areas with wolves than in areas without wolves. The highest vigilance level (47.5 ± 4.1%; mean ± SE) was seen by the second year for female elk with calves in the areas with wolves and was maintained during the subsequent 3 years of the study. As wolves ex- panded into non-wolf areas, female elk with and without calves in these areas gradually increased their vigilance levels from initially 20.1 ± 3.5 and 11.5 ± 0.9% to 43.0 ± 5.9 and 30.5 ± 2.8% by the fifth year of the study, respectively. We discuss the possible reasons for the differences seen among the social groups. We suggest that these behavioural re- sponses to the presence of wolves may have more far-reaching consequences for elk and bison ecology than the actual killing of individuals by wolves. 1409
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Many studies have examined grouping as a form of antipredator behaviour, but relatively few studies have examined how group size responds to natural variation in predation risk across space and through time. We studied the responses of elk, Cervus elaphus, herd size and composition to natural variation in the risk of predation by wolves, Canis lupus, in the Gallatin Canyon of Montana. We found that elk herd size increased as distance to protective cover increased. A positive association between group size and distance to cover is often interpreted as evidence that grouping is an antipredator response. However, we found that herd size increased only on days that wolves were absent. When wolves were present, herd sizes remained small at all distances from cover. This suggests that aggregation far from cover on days that wolves were absent was a foraging response, rather than an antipredator response. These data highlight interaction between temporal and spatial variation in predation risk, and suggest caution in conclusions about the antipredator benefits of grouping in the absence of direct data on risk or predator presence.
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Ecological theory predicts that the diffuse risk cues generated by wide-ranging, active predators should induce prey behavioural responses but not major, population- or community-level consequences. We evaluated the non-consumptive effects (NCEs) of an active predator, the grey wolf (Canis lupus), by simultaneously tracking wolves and the behaviour, body fat, and pregnancy of elk (Cervus elaphus), their primary prey in the Greater Yellowstone Ecosystem. When wolves approached within 1 km, elk increased their rates of movement, displacement and vigilance. Even in high-risk areas, however, these encounters occurred only once every 9 days. Ultimately, despite 20-fold variation in the frequency of encounters between wolves and individual elk, the risk of predation was not associated with elk body fat or pregnancy. Our findings suggest that the ecological consequences of actively hunting large carnivores, such as the wolf, are more likely transmitted by consumptive effects on prey survival than NCEs on prey behaviour.
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We compared movement patterns and rhythms of activity of a top predator, the Iberian lynx Lynx pardinus, a mesopredator, the red fox Vulpes vulpes, and their shared principal prey, the rabbit Oryctolagus cuniculus, in relation to moon phases. Because the three species are mostly nocturnal and crepuscular, we hypothesized that the shared prey would reduce its activity at most risky moon phases (i.e. during the brightest nights), but that fox, an intraguild prey of lynx, would avoid lynx activity peaks at the same time. Rabbits generally moved further from their core areas on darkest nights (i.e. new moon), using direct movements which minimize predation risk. Though rabbits responded to the increased predation risk by reducing their activity during the full moon, this response may require several days, and the moon effect we observed on the rabbits had, therefore, a temporal gap. Lynx activity patterns may be at least partially mirroring rabbit activity: around new moons, when rabbits moved furthest and were more active, lynxes reduced their travelling distances and their movements were concentrated in the core areas of their home ranges, which generally correspond to areas of high density of rabbits. Red foxes were more active during the darkest nights, when both the conditions for rabbit hunting were the best and lynxes moved less. On the one hand, foxes increased their activity when rabbits were further from their core areas and moved with more discrete displacements; on the other hand, fox activity in relation to the moon seemed to reduce dangerous encounters with its intraguild predator.
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Large herbivores are typically confronted by considerable spatial and temporal variation in forage abundance and predation risk. Although animals can employ a range of behaviours to balance these limiting factors, scale-dependent movement patterns are expected to be an effective strategy to reduce predation risk and opti-mise foraging opportunities. We tested this prediction by quantifying site fidelity of global positioning system-col-lared, non-migratory female elk (Cervus canadensis man-itobensis) across multiple nested temporal scales using a long-established elk–wolf (Canis lupus) system in Mani-toba, Canada. Using a hierarchical analytical approach, we determined the combined effect of forage abundance and predation risk on variation in site fidelity within four seasons across four nested temporal scales: monthly, biweekly, weekly, daily. Site fidelity of female elk was positively related to forage-rich habitat across all seasons and most temporal scales. At the biweekly, weekly and daily scales, elk became increasingly attached to low for-age habitat when risk was high (e.g. when wolves were close or pack sizes were large), which supports the notion that predator-avoidance movements lead to a trade-off between energetic requirements and safety. Unexpectedly, predation risk at the monthly scale increased fidelity, which may indicate that elk use multiple behavioural responses (e.g. movement, vigilance, and aggregation) simulta-neously to dilute predation risk, especially at longer tem-poral scales. Our study clearly shows that forage abundance and predation risk are important scale-depen-dent determinants of variation in site fidelity of non-migratory female elk and that their combined effect is most apparent at short temporal scales. Insight into the scale-dependent behavioural responses of ungulate populations to limiting factors such as predation risk and forage vari-ability is essential to infer the fitness costs incurred.
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Aspen in the Greater Yellowstone Ecosystem are hypothesized to be recovering from decades of heavy browsing by elk due to a behaviorally mediated trophic cascade (BMTC). Several authors have suggested that wolves interact with certain terrain features, creating places of high predation risk at fine spatial scales, and that elk avoid these places, which creates refugia for plants. This hypothesized BMTC could release aspen from elk browsing pressure, leading to a patchy recovery in places of high risk. I tested whether four specific, hypothesized fine-scale risk factors are correlated with changes in current elk browsing pressure on aspen, or with aspen recruitment since wolf reintroduction, in the Daly Creek drainage in Yellowstone National Park, and near two aspen enclosures outside of the park boundary. Aspen were not responding to hypothesized fine-scale risk factors in ways consistent with the current BMTC hypothesis.