No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
A ‘dynamic’ landscape of fear: prey responses to spatiotemporal variations in predation risk across the lunar cycle
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.
... To further improve the overall accuracy of the data, only images in which greater than 75% of volunteers agreed on the resulting species classification were included in our final dataset, increasing overall accuracy of volunteer classifications to 99% [64]. To minimize the potential for duplicated representation of an individual group (i.e. the same group repeatedly triggers a camera), we removed image sets of the same species that were captured at the same site within 10 min of each other [65], resulting in a single image set for each 'capture event'. ...
... Given the parameters of the cameras, animals in the same photo could be up to 14 m away from each other, if one individual was immediately in front of the camera and the other was at the maximum typical detection distance (see above). This distance, which corresponds to approximately 4-14 body lengths, falls within the range of nearest neighbour distances for group members in prior studies of these and similar species [16,65,68,69]. Although the precise social spacing of animals across the entire landscape is currently unknown, applying a standardized and biologically validated metric to classifying social interactions is needed to appropriately compare individuals or species [70]. ...
... We included three proxies of lion predation risk. First, we derived season-specific relative lion density at each camera trap location using long-term lion monitoring data (see [65] for details). We also included the distance from the sighting (camera) to the nearest rocky outcropping, called a kopje. ...
Despite continued interest in mixed-species groups, we still lack a unified understanding of how ecological and social processes work across scales to influence group formation. Recent work has revealed ecological correlates of mixed-species group formation, but the mechanisms by which concomitant social dynamics produce these patterns, if at all, is unknown. Here, we use camera trap data for six mammalian grazer species in Serengeti National Park. Building on previous work, we found that ecological variables, and especially forage quality, influenced the chances of species overlap over small spatio-temporal scales (i.e. on the scales of several metres and hours). Migratory species (gazelle, wildebeest and zebra) were more likely to have heterospecific partners available in sites with higher forage quality, but the opposite was true for resident species (buffalo, hartebeest and topi). These findings illuminate the circumstances under which mixed-species group formation is even possible. Next, we found that greater heterospecific availability was associated with an increased probability of mixed-species group formation in gazelle, hartebeest, wildebeest and zebra, but ecological variables did not further shape these patterns. Overall, our results are consistent with a model whereby ecological and social drivers of group formation are species-specific and operate on different spatio-temporal scales.
This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’.
... Prey may modulate behavior based on the predictable timing of predator activity (Kohl et al., 2018;Smith et al., 2019a) or their own energetic state (Kotler, Brown, & Bouskilla, 2004). They may modulate behavior based on extrinsic environmental dynamics that alter baseline risk (Palmer et al., 2017) and resource availability (Kotler et al., 2002), or due to interactions between extrinsic and intrinsic factors (Kotler et al., 2010). Similarly, variation in energetic state and trade-offs between the likelihood of prey capture and the likelihood of incurring an injury during an attack may shape variation in predator tactics . ...
... Similarly, variation in energetic state and trade-offs between the likelihood of prey capture and the likelihood of incurring an injury during an attack may shape variation in predator tactics . Ignoring these dynamics and other types of heterogeneity can also distort inferences about risk responses or other effects (Palmer et al., 2017). One would expect predator-prey games to exhibit seasonal dynamics (Kotler, Brown, Bouskila, et al., 2004), particularly in systems where the distribution and abundance of prey forage changes across the year and shapes predictable dynamics in prey foraging state and reproductive phenology. ...
... We used a broad array of camera traps to gain insights into variation into predator time-allocation (space use), and prey time-allocation, foraging, and vigilance in relation to both near and longer-term risk metrics and a suite of static and dynamic contextual factors. Camera-traps are widely used for exploring prey risk-response (e.g., Flagel et al., 2016;Gallo et al., 2019;Palmer et al., 2017), but there has been little work that explores reponse variation and dynamics across different phases of the predator-prey behavioral interaction (Suraci et al., 2022). ...
Predators and prey engage in games where each player must counter the moves of the other, and these games include multiple phases operating at different spatiotemporal scales. Recent work has highlighted potential issues related to scale‐sensitive inferences in predator–prey interactions, and there is growing appreciation that these may exhibit pronounced but predictable dynamics. Motivated by previous assertions about effects arising from foraging games between white‐tailed deer and canid predators (coyotes and wolves), we used a large and year‐round network of trail cameras to characterize deer and predator foraging games, with a particular focus on clarifying its temporal scale and seasonal variation. Linear features were strongly associated with predator detection rates, suggesting these play a central role in canid foraging tactics by expediting movement. Consistent with expectations for prey contending with highly mobile predators, deer responses were more sensitive to proximal risk metrics at finer spatiotemporal scales, suggesting that coarser but more commonly used scales of analysis may miss useful insights into prey risk‐response. Time allocation appears to be a key tactic for deer risk management and was more strongly moderated by factors associated with forage or evasion heterogeneity (forest cover, snow and plant phenology) than factors associated with the likelihood of predator encounter (linear features). Trade‐offs between food and safety appeared to vary as much seasonally as spatially, with snow and vegetation phenology giving rise to a “phenology of fear”. Deer appear free to counter predators during milder times of year, but a combination of poor‐foraging state, reduced forage availability, greater movements costs, and reproductive state dampen responsiveness during winter. Pronounced intra‐annual variation in predator–prey interactions may be common in seasonal environments.
... Variety of inexpensive data is made available by using automated technique for extracting information thus enabling ways for protective measures. The addressed work focuses on computer vision for extracting information about the presence of animals [7][8][9][10]. Such methods are risky when dealt by humans. ...
... The proposed work establishes a machine learning technique called deep learning that creates tremendous revolutions in artificial intelligence in the current scenario particularly in computer vision [11]. Investigations are made on the efficiency of the deep learning technique for enabling various future researches by providing a way that is of low cost for providing information from webcam researches that are already in use [7][8][9][10]. The working of CNN requires large number of labelled images, materials for computation and newly available architecture of neural network. ...
... (30). Hand held characteristics are harnessed on existing techniques for animal classification includes (8), where attempts are made to differentiate webcam recording that contain no animals (25) as well as the usage of support vector machine (14) for classification of images. They achieve an accuracy of 82%. ...
Comprehensive, Precise and real time data regarding the position and characteristics of animals is necessary for safeguarding visitors inside a wildlife sanctuary. Investigations are made on the capability for automated, unambiguous and economical collection of data that are useful to perform rescue operations within the sanctuary because of the absence of other communicational sources. Web camera enables collection of photos relating to wildlife economically, conservatively as well as regularly. Extraction of information from such photos is costly, slow and requires human intervention. The proposed system demonstrates the automatic extraction of such data using Convolutional Neural Network (CNN). Deep CNN is trained for a set of images available in a wildlife dataset.
... 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]. ...
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.
... Lion kill locations in the Serengeti ecosystem indicate that lions make kills where herbivores are more likely to be caught based on landscape features, rather than where herbivores are most abundant (Hopcraft et al., 2005). Meso-herbivores respond by either avoiding high-kill-risk landscapes or adapting their behavior to reduce the likelihood of being killed (Anderson et al., 2010;Hopcraft et al., 2012;Palmer et al., 2017). We used kill risk probability density estimates for each camera in the SS grid extracted from a kernel density distribution created using over 2500 historic lion kill locations of six common herbivore species (see Palmer et al., 2017). ...
... Meso-herbivores respond by either avoiding high-kill-risk landscapes or adapting their behavior to reduce the likelihood of being killed (Anderson et al., 2010;Hopcraft et al., 2012;Palmer et al., 2017). We used kill risk probability density estimates for each camera in the SS grid extracted from a kernel density distribution created using over 2500 historic lion kill locations of six common herbivore species (see Palmer et al., 2017). Historical lion collar data indicate that the western section of the SS grid has the highest density of lions (Swanson et al., 2014). ...
... The Serengeti ecosystem has one of the highest mammalian herbivore densities in the world (Campbell & Borner, 1995). High herbivore densities, in combination with documented trends in herbivore behavioral responses to carnivores (Anderson et al., 2010;Hopcraft et al., 2012;Palmer et al., 2017) would seem to set the stage for a system with good potential for observable large-carnivore-driven cascades. However, although browsers and grazers changed tree seedling establishment probabilities in our study, we found no evidence that the behavior of herbivores in response to a landscape of fear resulted in cascading effects on the spatial dynamics of tree seedling establishment (Aim 2). ...
In savanna ecosystems, fire and herbivory alter the competitive relationship between trees and grasses. Mechanistically, grazing herbivores favor trees by removing grass, which reduces tree‐grass competition and limits fire. Conversely, browsing herbivores consume trees and limit their recovery from fire. Herbivore feeding decisions are in turn shaped by risk‐resource trade‐offs that potentially determine the spatial patterns of herbivory. Identifying the dominant mechanistic pathways by which fire and herbivores control tree cover remains challenging, but is essential for understanding savanna dynamics. We used an experiment in the Serengeti ecosystem and a simple simulation driven by experimental results to address two main aims: (1) determine the importance of direct and indirect effects of grass, fire and herbivory on seedling establishment; and (2) establish whether predators determine the spatial pattern of successful seedling establishment via effects on mesoherbivore distribution. We transplanted tree seedlings into plots with a factorial combination of grass and herbivores (present/absent) across a lion kill‐risk gradient in the Serengeti, burning half of the plots near the end of the experiment. Ungrazed grass limited tree seedling survival directly via competition, indirectly via fire, and by slowing seedling growth, which drove higher seedling mortality during fires. These effects restricted seedling establishment to below 18% and, in conjunction with browsing, resulted in seedling establishment dropping below 5%. In the absence of browsing and fire, grazing drove a 7.5‐fold increase in seedling establishment. Lion predation risk had no observable impact on herbivore effects on seedling establishment. The severe negative effects of grass on seedling mortality suggests that regional patterns of tree cover and fire may overestimate the role of fire in limiting tree cover, with regular fires representing a proxy for the competitive effects of grass.
... Consequently, prey species frequently adopt two behavioral strategies in order to actively minimize risk; avoidance of areas perceived as high risk (Coleman & Hill, 2014a;Creel et al., 2005;Lima & Dill, 1990;Thaker et al., 2011;Valeix et al., 2009;Willems & Hill, 2009), or modification of behavior at a given location. Specifically, in areas perceived as high-risk prey species may actively increase vigilance levels (Campos & Fedigan, 2014;Laundré et al., 2001), alter movement patterns (Fischhoff et al., 2007;Fortin et al., 2005;Willems & Hill, 2009), shift activity patterns toward less risky times (Bonnot et al., 2013;Palmer et al., 2017;Valeix et al., 2009), or increase group size/cohesion (LaBarge et al., 2020;Lima, 1995;Scott-Samuel et al., 2015). However, these behavioral strategies to minimize risk must often be balanced with other behaviors critical to survival, such as acquiring food, meaning nearly all antipredator behaviors involve some element of cost (Lima & Dill, 1990). ...
... Similarly, De Vos et al. (2015) found that Cape fur seals (Arctocephalus pusillus pusillus) in South Africa preferred safe, shallow waters when engaging in social and thermoregulatory behaviors, where risk from white shark (Carcharodon carcharias) predation was reduced. Furthermore, Palmer et al. (2017) found that both African buffalo (Syncerus caffer) and common wildebeest (Connochaetes taurinus) in Tanzania increased their levels of relaxed behaviors during the wet season in areas where encounter risk with lions was low. In contrast, relaxed behaviors were more common in plains zebra (Equus quagga) during low-risk periods in the dry season (Palmer et al., 2017). ...
... Furthermore, Palmer et al. (2017) found that both African buffalo (Syncerus caffer) and common wildebeest (Connochaetes taurinus) in Tanzania increased their levels of relaxed behaviors during the wet season in areas where encounter risk with lions was low. In contrast, relaxed behaviors were more common in plains zebra (Equus quagga) during low-risk periods in the dry season (Palmer et al., 2017). ...
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.
... The perceived risk of predation is well known to influence wildlife behavior [1,2], creating a "landscape of fear" where species alter their behavior in, or avoid, regions of higher perceived risk [3,4]. Human disturbance can also induce fear responses in wildlife, altering feeding times, increasing vigilance or flight responses, or prompting species to select habitats with lower perceived human influence [5][6][7][8][9]. ...
... Life history traits may also influence species' responses to human disturbance [26], accentuating the importance of species-specific approaches to investigating wildlife diel activity shifts in response to human activity. Wildlife diel activity patterns can also vary with environmental factors such as lunar phase and forest cover due to associated variation in predation risk or hunting success [1,39,40]. Hence, it is crucial to consider a number of factors when investigating anthropogenic effects on wildlife nocturnality. Likewise, reliable methods for investigating these phenomena require careful consideration not only of species-specific traits, but also how to most effectively characterize metrics of both wildlife and human activity. ...
Wildlife species may shift towards more nocturnal behavior in areas of higher human influence, but it is unclear how consistent this shift might be. We investigated how humans impact large mammal diel activities in a heavily recreated protected area and an adjacent university-managed forest in southwest British Columbia, Canada. We used camera trap detections of humans and wildlife, along with data on land-use infrastructure (e.g., recreation trails and restricted-access roads), in Bayesian regression models to investigate impacts of human disturbance on wildlife nocturnality. We found moderate evidence that black bears (Ursus americanus) were more nocturnal in response to human detections (mean posterior estimate = 0.35, 90% credible interval = 0.04 to 0.65), but no other clear relationships between wildlife nocturnality and human detections. However, we found evidence that coyotes (Canis latrans) (estimates = 0.81, 95% CI = 0.46 to 1.17) were more nocturnal and snowshoe hares (Lepus americanus) (estimate = -0.87, 95% CI = -1.29 to -0.46) were less nocturnal in areas of higher trail density. We also found that coyotes (estimate = -0.87, 95% CI = -1.29 to -0.46) and cougars (Puma concolor) (estimate = -1.14, 90% CI = -2.16 to -0.12) were less nocturnal in areas of greater road density. Furthermore, coyotes, black-tailed deer (Odocoileus hemionus), and snowshoe hares were moderately more nocturnal in areas near urban-wildland boundaries (estimates and 90% CIs: coyote = -0.29, -0.55 to -0.04, black-tailed deer = -0.25, -0.45 to -0.04, snowshoe hare = -0.24, -0.46 to -0.01). Our findings imply anthropogenic landscape features may influence medium to large-sized mammal diel activities more than direct human presence. While increased nocturnality may be a promising mechanism for human-wildlife coexistence, shifts in temporal activity can also have negative repercussions for wildlife, warranting further research into the causes and consequences of wildlife responses to increasingly human-dominated landscapes.
... However, local hunting communities in Hawaiʻi have observed feral goats to be active at night during full moon phases. The lunar cycle does alter night-time visibility influencing predatory success but with varying, species-dependent prey responses (Palmer et al. 2017). However, in general, increased luminosity of the moon force prey to be less active and conversely show greater movements during the darkest periods (i.e., new moon) (Clarke 1983, Kotler et al. 2010, Penteriani et al. 2013. ...
... We hypothesized that feral goats would be more active during the day supported by other studies designating goats and other small ruminants as diurnal species (Piccione et al. 2008, O'Brien 1988, Shi et al. 2006). However, our data has showed greater activity at night, similar to nocturnal behavior of other animals, as described above (Clarke 1983, Kotler et al. 2010, Palmer et al. 2017, Penteriani et al. 2013. We speculate on the possibility that nocturnal movements could be due to pressures put on by feral dog packs known to roam this area. ...
... 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). ...
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). ...
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.
... 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). ...
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.
... 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). ...
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.
... Felids frequently hunt at night and, as such, may be greatly influenced by varying luminosity across moon phases [18]. Studies on the effects of lunar phase on wildlife are limited and have largely focused on prey species [30,31]. Less is known about the behavior of nocturnal predators in response to shifting lunar phase. ...
Various landscape and environmental factors influence animal movement and habitat selection. Lunar illumination affects nocturnal visual perception of many species and, consequently, may influence animal activity and habitat selection. However, the effects of varying moon stage may differ across taxa. Prey species often reduce activity during highly visible periods of night while predators may increase activity or alter their habitat use. Ocelots ( Leopardus pardalis ) and bobcats ( Lynx rufus ), two nocturnal predatory felids that coexist in southern Texas, may also alter their behavior in response to the phase of the moon. To evaluate the effects of lunar phase on habitat selection of ocelots and bobcats, we executed a step selection analysis using high-frequency GPS-telemetry data collected on each species (ocelot, N = 8; bobcat, N = 13) in southern Texas during 2017–2021 and compared step length during new versus full moons. We predicted that ocelots would increase use of dense thornshrub to reduce their visibility during a full moon. However, as bobcats are habitat generalists and are more active during crepuscular periods, we predicted less influence of moon phase on activity. Ocelots did not alter habitat selection in response to lunar phase but moved shorter distances during full moon phases. Conversely, bobcats selected for greater vegetation cover during full moons, possibly to facilitate hunting during brighter periods, but exhibited no difference in movement across lunar phase. We provide, to our knowledge, the first example of habitat selection by predators in relation to lunar phase and show differences across new versus full moons by ocelots and bobcats such that ocelots alter step length but not habitat selection while bobcats altered habitat selection but not step length in response to shifting lunar phase. Further, we suggest the high potential for ocelot-vehicle collisions on darker nights due to increased movement by ocelots and poor visibility for drivers.
... Such competition may be seasonal in nature as shared and alternative prey resources change in abundance and availability, which underscores the importance of considering intra-annual variation when examining the coexistence of competing species. Such variation has been long recognized as important in classical theory (e.g., Wiens, 1977) but is generally understudied in carnivore communities (Moll et al., 2021;Palmer et al., 2017). Similarly, our results support the long-held but often debated idea that interspecific competition at higher latitudes and in harsher environments is less limiting than in climatic conditions (MacArthur, 1972). ...
Investigating species responses to trophic interactions and abiotic factors is crucial to better understanding their ecology and creating effective management strategies. In carnivore communities, smaller species are often regulated by larger ones via top‐down interference competition. Smaller subordinate carnivores can also be regulated by bottom‐up and abiotic factors, such as the availability of important prey, habitat features, and climatic conditions. However, substantial ambiguity remains regarding the relative roles these complex factors play in shaping subordinate carnivore populations, especially during winter. To investigate this issue, we conducted a large‐scale camera‐trapping study ( n = 197 sites distributed across a ~60,000 km ² landscape) using a balanced study design that sampled a gradient of forest disturbance and climatic conditions. We used dynamic occupancy modeling to examine the influences of top‐down (interference competition), bottom‐up (prey and habitat), and abiotic (climate) factors on a widespread, generalist subordinate carnivore, the red fox ( Vulpes vulpes ), in Maine, USA. Across three winters, we collected 107 red fox and 185 coyote ( Canis latrans ) daily detections, and 3875 snowshoe hare ( Lepus americanus ) detections. We found evidence for the top‐down effects of coyotes on red fox detection probability and site colonization. However, contrary to theoretical expectations, the association between coyotes and red foxes was positive rather than negative. Snowshoe hares had a positive association with local extinction by red foxes, which also contrasts with prevailing theory given that snowshoe hares are an important winter prey of red foxes in this ecosystem. The intensity of forest disturbance and the proportion of conifer forest had negative effects on red fox occurrence and detection probability, while snow depth had a strong negative effect on site colonization. Together, these results suggest red foxes are limited more by abiotic and bottom‐up factors related to habitat than by the top‐down interference competition or primary prey availability in winter. Our study supports recent findings that bottom‐up factors may shape carnivore distributions during less productive times of year. Our work also highlights how caution is needed when extrapolating previous results from summer studies to winter, as the role of top‐down and bottom‐up factors may change seasonally.
... Environmental factors such as lunar illumination influence nocturnal prey and predators' activity patterns (Prugh and Golden 2014), and by extension how prey respond to predation risk (Griffin et al. 2005; Navarro-Castilla and Barja 2014). The predation risk allocation hypothesis (Lima and Bednekoff 1999) predicts that if predators were more successful with increasing lunar illumination, prey species would become lunar phobic and shift activity to less bright lunar phases where possible (Palmer et al. 2017). Another possibility is that prey may shift away from behavior that increases their vulnerability during risky time periods, decreasing their exposure by altering their activity budget. ...
Behavioral adjustments to predation risk not only impose costs on prey species themselves but can also have cascading impacts on whole ecosystems. The greater bilby (Macrotis lagotis) is an important ecosystem engineer, modifying the physical environment through their digging activity, and supporting a diverse range of sympatric species that use its burrows for refuge and food resources. The bilby has experienced a severe decline over the last 200 years, and the species is now restricted to ~20% of its former distribution. Introduced predators, such as the feral cat (Felis catus), have contributed to this decline. We used camera traps to monitor bilby burrows at four sites in Western Australia, where bilbies were exposed to varying levels of cat predation threat. We investigated the impact of feral cats on bilby behavior at burrows, particularly during highly vulnerable periods when they dig and clear away soil or debris from the burrow entrance as they perform burrow maintenance. There was little evidence that bilbies avoided burrows that were visited by a feral cat; however, bilbies reduced the time spent performing burrow maintenance in the days following a cat visit (P = 0.010). We found the risk posed to bilbies varied over time, with twice the cat activity around full moon compared with dark nights. Given bilby burrows are an important resource in Australian ecosystems, predation by feral cats and the indirect impact of cats on bilby behavior may have substantial ecosystem function implications.
... M. Brunell, Florida Fish and Wildlife Conservation Commission, personal communication) and threat of alligator predation is probable for white-tailed deer in wetlands. A spatiotemporal shift in the landscape of fear (Gaynor et al., 2019;Palmer et al., 2017) for white-tailed deer might occur due to the long-wavelength enrichment with cloudy weather during twilight. White-tailed deer are less sensitive to long wavelengths with a sharp decline in sensitivity at wavelengths >600 nm (Cohen et al., 2014;Jacobs et al., 1994), while alligators have a long-wave sensitive cone with a peak sensitivity of 566 nm and minimal drop-off at wavelengths >600 nm (Shoop and Ruckdeschel, 1990;Sillman et al., 1991). ...
Visual perception is dynamic and depends on physiological properties of a species’ visual system and physical characteristics of the environment. White-tailed deer (Odocoileus virginianus) are most sensitive to short- and mid-wavelength light (e.g. blue and green). Wavelength enrichment varies spatially and temporally across the landscape. We assessed how the visual perception of deer influences their movement decisions. From August to September 2019, we recorded 10-min locations from 15 GPS-collared adult male deer in Central Florida. We used Hidden-Markov models to identify periods of movement by deer and subset these data into three time periods based on temporal changes in light environments. We modeled resource selection during movement using path-selection functions and simulated 10 available paths for every path used. We developed five a priori models and used 10-fold cross validation to assess our top model's performance for each time period. During the day, deer selected to move through woodland shade, avoided forest shade, and neither selected nor avoided small gaps. At twilight, deer avoided wetlands as cloud cover increased but neither selected nor avoided other cover types. Visual cues and signals are likely more conspicuous to deer in short-wavelength-enriched woodland shade during the day, while at twilight in long-wavelength-enriched wetlands during cloud cover, visual cues are likely less conspicuous. The nocturnal light environment did not influence resource selection and likely has little effect on deer movements because it's relatively homogenous. Our findings suggest visual perception relative to light environments is likely an underappreciated driver of behaviors and decision-making by an ungulate prey species.
... In response, prey species exhibit a varying anti-predatory behavior across the lunar cycle. For example, wildebeest (Connochaetes taurinus) and zebra (Equus quagga) avoid foraging near lions, while zebra and buffalo (Syncerus caffer) tend to form large herds during the new moon in certain areas like SNP (Palmer et al., 2017). However, in Kruger National Park, nocturnal movements of wildebeest and zebra were largely influenced by their proximity to the lions rather than moon phase (Traill et al., 2016). ...
Roads within protected areas facilitate management and tourism but can also alter animal movements and foraging opportunities. Animal tracks observed along roads are also used to index species distributions and abundance. We investigated the influence of roads on lion (Panthera leo) movements within the Serengeti ecosystem of Tanzania. We used hourly locations from 18 GPS-collared lions to quantify the influence of temporal periodicity (diel, lunar, and seasonal) and land covers on lion road use and road crossing frequency during 2018-2019. Lion road use and crossings did not differ between day and night but varied up to 63% across lunar illumination and 82% between seasons. Greater lion road use and road crossing incidents observed during the dry season and greater lunar illumination can be attributed to reduced foraging because lion prey are less common during the dry season and acquired at a lower success rate during periods of greater lunar illumination. As lion road use varied between seasons and across lunar phases, we recommend consideration of these variations when indexing lion populations using data derived from track surveys that use roads as transects.
... The reproductive activity of many reef organisms is linked to the lunar cycle. This environmental factor affects the probability of transport away from the coastal environment (tidal advection) and the predation risk, since it modulates the vertical migration rhythm of predators sensitive to moonlight (e.g., Tarling et al. 1999;Benoit-Bird et al. 2009;Hernandez-Leon et al. 2010;Palmer et al. 2017). Synchronicity between lunar phases and larval emission has been proposed for breeding corals, including the genus Tubastraea (Fan et al 2002;Lin 2005;Zakai et al. 2006;Crowder et al. 2014), but based on the available literature no clear pattern is evident for sun corals. ...
The mechanical removal of sun corals, Tubastraea spp., is currently the most applied method to reduce its spread along the Brazilian coast. The design of efficient control protocols requires understanding the effects of stress on these organisms when applying removal procedures. Here, we record larval release in sun corals immediately after colony removal from the natural substrate and investigate the potential influence of environmental conditions on planulation. Data were collected in ten field campaigns over 2 years of study. We detected the emission of a large number of larvae in short-duration events, during the spring (December 2017 and October 2019), when the moon was in the Second Quarter and New Moon phases. Apart from the two larval emission peaks, planulation remained low or null during the study. In addition, we noted a significant decrease in larval emission levels when seawater temperatures are below 24.5 °C, so this factor limits the dispersal potential of sun coral. On the other hand, under warmer conditions (≥ 24.5, < 27.2 °C), we recorded increases in larval release rates along with rises in seawater turbidity (≥ 1.2, < 2.4 NTU), which modulates the planulation in this suspensivore coral. Considering this, together with complementary laboratory observations, we propose that larval emission in sun corals responds to shared stimuli for feeding and reproduction, as a consequence of the simplicity in structural design in cnidarians. The number of polyps per colony had no effect on larval release rates for the colony sizes assessed. Simultaneously to the field work, we monitored the fecundity dynamics in specimens of sun coral kept in cultures—located in the vicinity of the study area—finding similar patterns to those registered in the field. Although sun corals reproduce throughout the year, a large number of larvae may be released within short periods of time and with short intervals among emissions. As a result of this mixed larval release strategy, Tubastraea spp. has the potential to recruit in a wide variety of environmental conditions. Under favorable situations, sun corals may exert a “propagule pressure” impact on native communities, which explains the success of its numerous invasions. We conclude that (1) when mechanical removal is applied to control sun coral propagation, the dynamic of reproductive activity associated with variations in environmental conditions should be considered to minimize larval dissemination, and (2) laboratory-based sun coral monitoring may support more efficient implementation of control protocols.
... It requires significant time investment, and its outcome limits the energy available for other activities. Many factors can affect decisions of foragers, including both intrinsic factors such as hunger level (Talling et al. 2002), sex (Di Stefano et al. 2009) or personality (Mella et al. 2015;Herath et al. 2021), and extrinsic factors such as predation (Palmer et al. 2017) and thermal risks (Trillmich and Trillmich 1986). But, the most obvious factors affecting foraging decisions are associated with foods themselves, such as their abundance, nutritional value, and toxic costs, and the effort required by foragers to handle and process them (e.g., Wiggins et al. 2003;Marsh et al. 2007;Frye et al. 2013). ...
When foraging, making appropriate food choices is crucial to an animal’s fitness. Classic foraging ecology theories assume animals choose food of greatest benefit based on their absolute value across multiple dimensions. Consequently, poorer options are considered irrelevant alternatives that should not influence decision-making among better options. But heuristic studies demonstrate that irrelevant alternatives (termed decoys) can influence the decisions of some animals, indicating they use a relative rather than absolute evaluation system. Our aim was to test whether a decoy influenced the decision-making process—that is, information-gathering and food choice—of a free-ranging mammalian herbivore. We tested swamp wallabies, Wallabia bicolor, comparing their behavior toward, and choice of, two available food options over time in the absence or presence of the decoy. We used a phantom decoy—unavailable option—and ran two trials in different locations and seasons. Binary preferences (decoy absent) for the two available food options differed between trials. Irrespective of this difference, across both trials the presence of the decoy resulted in animals more likely to overtly investigate available food options. But, the decoy only shifted food choice, weakly, in one trial. Our results indicate that the decoy influenced the information-gathering behavior during decision-making, providing the first evidence that decoys can affect decision-making process of free-ranging mammalian herbivores in an ecologically realistic context. It is premature to say these findings confirm the use of relative evaluation systems. Whether the foraging outcome is more strongly affected by other decoys, food dimensions, or ecological contexts, is yet to be determined.
... Takemura et al. (2010) reported that the intensity of the light from the moon influences the physiological and behavioral activities of fish inhabiting tropical and subtropical waters. Indeed, the lunar cycle plays a relevant role in influencing the biological rhythms of fish, and has an effect on reproduction (Oliveira et al., 2009;Ikegami et al., 2014;Golmoradizadeh et al., 2021), molecular mechanisms (Steindal and Whitmore, 2019;Andreatta and Tessmar-Raible, 2020), predation behavior (Palmer et al., 2017) and the release of hormones such as melatonin and sexual steroids (Oliveira et al., 2010). Biological rhythms, irrespectively from being a direct response to the environment or driven by endogenous oscillators, are also mediated by changes in hormonal levels and metabolism (Pittendrigh, 1960;Ali, 1992). ...
Lunar cycle modulates the rhythmic activity patterns of many animals, including fish. The effect of the moonlight cycle on daily melatonin and metabolic parameters was evaluated in matrinxã (Brycon amazonicus) subjected to external natural lighting. Eighty juvenile were distributed in 4 tanks of 1m3 (20 fish/tank) and divided into two groups. One group was exposed to the full moon and the other group to the new moon for 30 days, which corresponds to the duration of the lunar period. At the end of the lunar phase, 6 fish from each group were anesthetized to collect blood, tissue and eye samples at midday and midnight. The comparison between the light and dark periods revealed a significant increase in plasma and ocular melatonin in the last period. However, there was no significant difference for plasma melatonin between moons. Ocular melatonin presented higher concentrations during the new moon. Glucose, total proteins, cortisol, liver glutathione and gill lipid peroxidation were higher in the full moon compared to in the new moon. Plasma triglyceride was higher during the night for the full moon, and the opposite was found for the new moon. Total cholesterol values were higher at night regardless the moon phase. Glutathione in the gills and lipid peroxidation in the liver showed no significant differences. These results highlight the importance of considering both the day and lunar cycles for melatonin and metabolic parameters in species of commercial interest and susceptible to stressful situations in rearing conditions.
... Approximately sixty-nine percent of mammals are nocturnal 17 , thus changes in moonlight over the lunar cycle is expected to influence the behaviour of many species 18 . Increased moonlight can improve the hunting efficiency of both mammalian and non-mammalian predators 19,20 , resulting in increased predation risk and reduced activity for prey species [21][22][23][24] . ...
Predation influences prey survival and drives evolution of anti-predator behaviour. Anti-predator strategies by prey are stimulated by direct encounters with predators, but also by exposure to indicators of risk such as moonlight illumination and vegetation cover. Many prey species will suffer increased risk on moonlit nights, but risk may be reduced by the presence of dense vegetation. Determining the role of vegetation in reducing perceived risk is important, especially given predictions of increased global wildfire, which consumes vegetation and increases predation. We used remote cameras in southeastern Australia to compare support for the predation risk and habitat-mediated predation risk hypotheses. We examined the influence of moonlight and understorey cover on seven 20–2500 g mammalian prey species and two introduced predators, red foxes and feral cats. Activity of all prey species reduced by 40–70% with increasing moonlight, while one species (bush rat) reduced activity in response to increasing moonlight more sharply in low compared to high understorey cover. Neither predator responded to moonlight. Our findings supported the predation risk hypothesis and provided limited support for the habitat-mediated predation risk hypothesis. For prey, perceived costs of increased predation risk on moonlit nights outweighed any benefits of a brighter foraging environment.
... For instance, the rise in the activity of dusky grouper as the luminosity decreases could be related to an increase in hunting success. Low-light periods such as night or during the new moon phase, might be more advantageous for a predator such as the dusky grouper, as the prey might have more difficulties to warn of their presence (Palmer et al., 2017). Related to the water temperature, our findings agree with existing scientific literature, which underlines its close relationship with bioenergetics (i.e., energetic cost of movement increases exponentially beyond certain temperature ranges) and its crucial role in the behaviour of many aquatic species (Schlaff et al., 2014;Ladich, 2018). ...
The rise of nature-based tourism has provided a new avenue for disturbing animal behaviour, especially in protected areas. One of the most important tourism sectors in aquatic environments is scuba diving, an activity considered sustainable given its non-extractive nature and capability of bringing relevant socioeconomic benefits to local communities. However, knowledge about its impact on the activity patterns of aquatic animals is still scarce. Here, we used biotelemetry techniques to assess the importance of scuba diving in modulating the activity patterns of the dusky grouper (Epinephelus marginatus, Lowe, 1834), a marine predatory fish of high interest for fishing and tourism. We implemented Hidden Markov Models (HMMs) on high-resolution acceleration data using a temporal and spatial control while controlling for a set of environmental variables (i.e. photoperiod, time-of-day, moon phase, temperature, wave height, and intensity and direction of marine currents) within a multiple-use marine protected area, and diving tourism hot-spot, of the western Mediterranean Sea. Our results underlined the more decisive influence of environmental-related stressors on the activity patterns of the dusky grouper compared to the impact of scuba diving. A high heterogeneity existed in the response against most of the stressors, including the presence of scuba divers. Overall, the activity of dusky grouper was higher at night than at day, showing a positive relationship with wave height, water temperature, and current intensity and a negative one with the moon phase. Remarkably, our findings, based on novel biotelemetry tools, differed substantially from the common wisdom accepted for this species. In conclusion, there is no clear evidence of scuba divers influence on the general activity patterns of the dusky grouper. Beyond their relevance from an ecological perspective, these results provide useful insights for the sustainable management of coastal resources, suggesting that scuba diving, when properly carried out, can represent an important sector to foster for the blue growth of coastal communities.
... This contradiction in past findings can be attributed to the variability in predator abundances between these two study sites (Kronfeld-Scho et al. 2013, Lim & Mojiol 2021. High lunar illumination can increase the visual acuity of terrestrial mammals in detecting other approaching wildlife individuals and exposes its presence to predators, particularly in the open environment of the mineral lick (Roschlau & Scheibler 2015, Palmer et al. 2017. Because of that, predator abundance plays a crucial role in defining the pattern of a mammal species visiting the mineral lick at night. ...
The most common visitors to the natural mineral licks in Sabah, Borneo, are the large even-toed ungulates, but their nocturnal activity patterns are influenced by the moon phase and interspecific competition. A camera trapping survey was conducted to examine the nocturnal activity patterns adopted by the large even-toed ungulate species in visiting four selected mineral licks in Segaliud-Lokan Forest Reserve across different moon phases. A total of 436 independent sightings of three large even-toed ungulate species were recorded within 345 nights of camera trapping in this research. The herbivorous-frugivorous Sambar Deer (Rusa unicolor) was found competing with the omnivorous Bearded Pig (Sus barbatus) for the usages of mineral licks under the same temporal niche. The activity level of the herbivorous-frugivorous Banteng (Bos javanicus) at night was dependent only on the existing lunar illumination. The present findings suggest that the change in lunar illumination can define the predation risk and visual acuity of terrestrial mammals. However, these influences are likely to have less of an impact on species with high lick dependency, such as the Sambar Deer and Bearded Pig at this forest reserve, especially when predator abundance is low, although further research is required to confirm the given matters in the future.
... Furthermore, since resources and risks vary across both space and time, animal community compositions are rarely stable but rather follow patterns reflecting local landscape dynamics (Giller, 2012;Palmer et al., 2017). In SE Asian forests, protected areas are frequently bordered by indigenous communities, who practice traditional forest management and subsistence hunting (Bennett et al., 2000;Cairns, 2015;Mertz et al., 2013). ...
Understanding wildlife spatiotemporal dynamics at protected area boundaries is critical to conservation. In SE Asia, protected areas are often bordered by indigenous communities whose traditional practices result in increased landscape heterogeneity within their community managed forests (CF). Because SE Asian forests exhibit supra‐annual mast fruiting (3–7 yrs) and sustained fruit scarcity, wildlife using CF may benefit from greater availability of fruits and seeds encouraged by traditional management, but incur greater risk of being hunted. We examined shifts in wildlife activity in forests within and adjacent to Lanjak Entimau Wildlife Sanctuary (LEWS), in Sarawak, Malaysia. Using camera traps and surveys of fruiting phenology, we related presence of fruits and seeds to shifts in large mammal activity over 3 years (October 2016–2019). We first compared relative frequency of five focal species (sun bear, bearded pig, muntjac, mouse deer, and sambar) by forest type for a given survey year and season (rainy vs. dry). We then modeled activity to assess how fruit availability, landscape features, and proxies for hunting risk, influence seasonal shifts in habitat use. Our results suggested seasonal variation in concert with increased landscape heterogeneity influenced patterns of activity. We found no evidence that CF excluded any detected mammal species, suggesting CF contribute important habitat to wildlife, particularly during periods of fruit scarcity in primary forest. However, our findings also imply increased hunting risk for wildlife attracted to resources near human settlements, emphasizing the need to consider the influence of both annual and supra‐annual seasonality when developing best practices for the sustainable management.
... , is indisputable. A more useful emerging generalization is that the strength and form of herbivore response -and hence trophic cascades -depends on the spatiotemporal predictability of risk and the ability of large herbivores to adjust their behavior in ways that mitigate vulnerability without diminishing impact165,254,[257][258][259][260][261][262][263] . Experimental or quasi-experimental evidence of trophic cascades involving large herbivores and carnivores exists from multiple continents 77,264-266 , as do studies finding no evidence of trophic cascades despite strong predator-induced changes in herbivore behavior or density261,[267][268][269] . ...
Large herbivores play unique ecological roles and are disproportionately imperiled by human activity. As many wild populations dwindle towards extinction, and as interest grows in restoring lost biodiversity, research on large herbivores and their ecological impacts has intensified. Yet, results are often conflicting or contingent on local conditions, and new findings have challenged conventional wisdom, making it hard to discern general principles. Here, we review what is known about the ecosystem impacts of large her-bivores globally, identify key uncertainties, and suggest priorities to guide research. Many findings are generalizable across ecosystems: large herbivores consistently exert top-down control of plant demography , species composition, and biomass, thereby suppressing fires and the abundance of smaller animals. Other general patterns do not have clearly defined impacts: large herbivores respond to predation risk but the strength of trophic cascades is variable; large herbivores move vast quantities of seeds and nutrients but with poorly understood effects on vegetation and biogeochemistry. Questions of the greatest relevance for conservation and management are among the least certain, including effects on carbon storage and other ecosystem functions and the ability to predict outcomes of extinctions and reintroduc-tions. A unifying theme is the role of body size in regulating ecological impact. Small herbivores cannot fully substitute for large ones, and large-herbivore species are not functionally redundant-losing any, especially the largest, will alter net impact, helping to explain why livestock are poor surrogates for wild species. We advocate leveraging a broad spectrum of techniques to mechanistically explain how large-herbivore traits and environmental context interactively govern the ecological impacts of these animals.
... Being the putative molecular mechanisms that are still undetermined, moonlight intensity, geomagnetism, and gravity are argued to be more likely the primary causes of the periodic deviation in frequency or intensity for specific brain and body functions. Specifically, defense behavior and spacing, predatorprey dynamics [10,11], and systematic variations in birth rate, fertility, ovulation, and locomotor activity, are reported to be lunar-synchronized events in different species and that have particular adaptive values depending on the ecological niche of each aggrupation of organisms [12][13][14][15][16]. ...
Given energy costs for gestating and caring for male offspring are higher than those of female newborns, external environmental conditions might be regarded as likely to affect the timing of delivery processes differentially depending on the sex of the newborn calf to be delivered. The aim of the present paper is to evaluate the association between environmental stressors such as the moon phase and weather-related factors and the onset of labor in female dromedaries. A binary logistic regression model was developed to find the most parsimonious set of variables that are most effective in predicting the probability for a gravid female dromedary to give birth to a male or a female calf, assuming that higher gestational costs and longer labor times are ascribed to the production of a male offspring. Although the differences in the quantitative distribution of spontaneous onset of labor across lunar phases and the mean climate per onset event along the whole study period were deemed nonsignificant (p > 0.05), a non-negligible prediction effect of a new moon, mean wind speed and maximum wind gust was present. At slightly brighter nights and lower mean wind speeds, a calf is more likely to be male. This microevolutionary response to the external environment may have been driven by physiological and behavioral adaptation of metabolic economy and social ecology to give birth to cooperative groups with the best possible reduction of thermoregulatory demands. Model performance indexes then highlighted the heterothermic character of camels to greatly minimize the impact of the external environment. The overall results will also enrich the general knowledge of the interplay between homeostasis and arid and semi-arid environments.
... The difference found between the number of European robins and great tits visiting BFs probably depends on their life history (Palmer et al., 2017). A lower density of robins in the study area is probably due to winter territoriality (Lack, 1939), and the flocking behaviour of great tits outside the breeding period (Morse, 1978) probably explains the constant presence of this species at BFs during the period of video recording (March).The significantly higher number of visits in the middle of the day by great tits could be explained by habits linked with a major abundance of their food resources and their ability to detect these resources (in natural conditions) when light and temperature are at their optimal seasonal level. ...
Unlabelled:
In a development of the ecosemiotic vivo-scape concept, a 'safety eco-field' is proposed as a model of a species response to the safety of its environment. The safety eco-field is based on the ecosemiotic approach which considers environmental safety as a resource sought and chosen by individuals to counter predatory pressure. To test the relative safety of different locations within a landscape, 66 bird feeders (BF) were deployed in a regular 15 × 15 m grid in a rural area, surrounded by shrubs, small trees, hedgerows, and buildings. On each of 48 days in November 2021 and February and March 2022, dried mealworms were placed on each BF and counts of larvae at each BF were made at noon and dusk. The European robin (Erithacus rubecula) and the great tit (Parus major) were the most regular visitors to the BFs. Land cover at each BF was recorded. Bird behaviour at the BFs was noted from direct video recordings of the birds at nine selected BFs, totalling 32 daily sessions in March. The different behaviours of the European robin and the great tit were observable. The safety eco-field changed according to the month and the time of day. The distance of the BF from the woodland edges seemed to be important only in the morning. In the afternoon, BFs that were more distant from the woodland edges received the highest number of visits. Weather conditions were found to influence the number of mealworms removed, but this requires further investigation. A significant relationship between land cover and the number of mealworm larvae removed from the BFs was observed. Within the grid of BF, three regions were distinguishable which were related to land cover in the safety eco-field process. The experimental framework confirms the adequacy, at least for birds that have cryptic predators, to map the landscape as a proxy of safety resource. From the video recordings it was noted that the European robin visits were distributed throughout the day without apparent temporal preferences, while the great tit visits were concentrated in the central part of the day. This result has the limitation of the short period of observation (March) and should be extended to the entire period of the experiment to eventually capture seasonal variation. The experimental evidence obtained confirms that the ecosemiotic-based models of safety eco-field are an efficient approach to explain bird feeding preferences and behaviours.
Supplementary information:
The online version contains supplementary material available at 10.1007/s12304-023-09522-1.
... For instance, the rise in the activity of dusky grouper as the luminosity decreases could be related to an increase in hunting success. Low-light periods such as night or during the new moon phase, might be more advantageous for a predator such as the dusky grouper, as the prey might have more difficulties to warn of their presence (Palmer et al., 2017). Related to the water temperature, our findings agree with existing scientific literature, which underlines its close relationship with bioenergetics (i.e., energetic cost of movement increases exponentially beyond certain temperature ranges) and its crucial role in the behaviour of many aquatic species (Schlaff et al., 2014;Ladich, 2018). ...
... While most studies addressing the formation and benefits of home ranges have focused on the importance of exploiting patchily distributed resources (or restrictions in movement caused by aggressive defence by territorial neighbours 7,10,27 ), another critical factor that shapes natural selection and varies non-randomly across the landscape, is predation. Many predators, particularly ambush hunters, display fine-scale temporal and spatial patterning in their hunting behaviour 44 , which prey can potentially learn and mitigate through strategies such as increased vigilance, avoidance of high-risk areas or exploiting memorized escape routes 38,[44][45][46][47] . As such, there is growing evidence that predation risk may be particularly high in regions that prey are less familiar with 44,48,49 . ...
Most animals confine their activities to a discrete home range, long assumed to reflect the fitness benefits of obtaining spatial knowledge about the landscape. However, few empirical studies have linked spatial memory to home range development or determined how selection operates on spatial memory via the latter’s role in mediating space use. We assayed the cognitive ability of juvenile pheasants (Phasianus colchicus) reared under identical conditions before releasing them into the wild. Then, we used high-throughput tracking to record their movements as they developed their home ranges, and determined the location, timing and cause of mortality events. Individuals with greater spatial reference memory developed larger home ranges. Mortality risk from predators was highest at the periphery of an individual’s home range in areas where they had less experience and opportunity to obtain spatial information. Predation risk was lower in individuals with greater spatial memory and larger core home ranges, suggesting selection may operate on spatial memory by increasing the ability to learn about predation risk across the landscape. Our results reveal that spatial memory, determined from abstract cognitive assays, shapes home range development and variation, and suggests predation risk selects for spatial memory via experience-dependent spatial variation in mortality. After assaying the cognitive ability of juvenile pheasants and releasing them into a new landscape, the authors show that pheasants with better memory developed larger home range sizes and more successfully avoided predation at the edges of the home range.
... For example, stalk and ambush predators, which largely depend on some form of concealment to approach their prey 14,16 , may use darkness as a substitute for physical cover 18 and shift from diurnal to nocturnal hunting as habitats vary from closed to open, despite the main activity of their prey being diurnal [19][20][21] . Under such conditions, the effectiveness of darkness for concealment may decrease in relation to moon luminosity 18,22 , with predator hunting success varying with the moon phase 23 . ...
The daily and seasonal activity patterns of snow leopards (Panthera uncia) are poorly understood, limiting our ecological understanding and hampering our ability to mitigate threats such as climate change and retaliatory killing in response to livestock predation. We fitted GPS-collars with activity loggers to snow leopards, Siberian ibex (Capra sibirica: their main prey), and domestic goats (Capra hircus: common livestock prey) in Mongolia between 2009 and 2020. Snow leopards were facultatively nocturnal with season-specific crepuscular activity peaks: seasonal activity shifted towards night-sunrise during summer, and day-sunset in winter. Snow leopard activity was in contrast to their prey, which were consistently diurnal. We interpret these results in relation to: (1) darkness as concealment for snow leopards when stalking in an open landscape (nocturnal activity), (2) low-intermediate light preferred for predatory ambush in steep rocky terrain (dawn and dusk activity), and (3) seasonal activity adjustments to facilitate thermoregulation in an extreme environment. These patterns suggest that to minimise human-wildlife conflict, livestock should be corralled at night and dawn in summer, and dusk in winter. It is likely that climate change will intensify seasonal effects on the snow leopard's daily temporal niche for thermoregulation in the future.
... Emotional responses to biological threats may vary with time and with specific conditions [13,14]. Psychological responses to COVID-19 depend on what the average people believe about COVID-19, and their views may vary across the various waves of the pandemic. ...
COVID-19 represents an overwhelming stressor to mental health. Elderly individuals are particularly at risk, but it is still unclear whether the risk is equally distributed among men and women. The aim of this study was to define gender differences in persistent psychiatric symptoms after COVID-19 illness and to test their association with resilience factors. Methods: We assessed 348 individuals aged >65 years at a multidisciplinary post-COVID-19 service. Mood and anxiety symptoms were investigated, as well as psychological distress and resilience, as assessed with the Kessler-10 (K10) Scale and the Connor-Davidson Resilience Scale (CD-RISC), respectively. Multivariate and linear regression analyses were used to test the distribution patterns of psychiatric symptoms and resilience factors. Results: In the total sample, 214 (61.5%) were men (a mean age of 73.25 years ±6.04) and 134 (38.5%) were women (a mean age of 72.69 years ±6.43; p = 0.407). Men and women significantly differed in marital status (χ2 = 25.17; p < 0.001, more men were married), living alone (χ2 = 11.62; p < 0.01, fewer men were living alone), hospitalization during COVID-19 illness (χ2 = 12.35; p < 0.001, more men were hospitalized during COVID-19), and subjective health status before COVID-19 infection (χ2 = 4.32; p < 0.001, men reporting better subjective health than women). Women reported more psychiatric symptoms and fewer resilience factors than men. Low resilience levels significantly predicted psychological distress in both men and women. Conclusions: The female elderly population affected by COVID-19 showed a greater vulnerability to psychiatric symptoms. Our data point to the need to strengthen resilience resources, especially in women.
... Animals captured by camera traps were identified to species. We considered events independent if > 10 min elapsed between captures (Palmer et al., 2017), unless a different species was captured on camera. With the exception of caribou (Rangifer tarandus) herds foraging on den sites, almost all other capture events lasted < 10 min. ...
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 on 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 historical Arctic fox dens. We evaluated the impact of fox denning activity on the spatial behavior of other tundra wildlife by comparing predator and herbivore visits to 12 natal dens and adjacent control sites over two years 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, where they were observed investigating and scavenging prey remains (carrion, feathers), suggesting carcass presence or fox presence attracts predators to den sites. Caribou (Rangifer tarandus) also visited dens more often than control sites, likely attracted by the enhanced vegetation typically found on dens. Our results suggest fox ecosystem engineering affects the spatial distribution of herbivores by enriching vegetation at dens, and other predators by providing carrion. Understanding how predators affect other organisms via non-trophic interactions provides an enriched view of their functional roles within ecosystems.
... Although experimental manipulation provides the strongest evidence for fear-based responses, many past studies have inferred fear from observational data (e.g., Wooster et al., 2021). Fear response can manifest in many ways, including increased vigilance and avoidance of high risk areas and/or high risk times (Palmer et al., 2017). Here, we inferred ''fear'' by using a multispecies occupancy model with continuous-time detection process (Kellner et al., 2021) to assess the extent to which wildlife species were using human-dominated habitats and co-occuring with humans, spatially and temporally, while accounting for imperfect detection. ...
Wildlife alter their behaviors in a trade-off between consuming food and fear of becoming food themselves. The risk allocation hypothesis posits that variation in the scale, intensity and longevity of predation threats can influence the magnitude of antipredator behavioral responses. Hunting by humans represents a threat thought to be perceived by wildlife similar to how they perceive a top predator, although hunting intensity and duration varies widely around the world. Here we evaluate the effects of hunting pressure on wildlife by comparing how two communities of mammals under different management schemes differ in their relative abundance and response to humans. Using camera traps to survey wildlife across disturbance levels (yards, farms, forests) in similar landscapes in southern Germany and southeastern USA, we tested the prediction of the risk allocation hypothesis: that the higher intensity and longevity of hunting in Germany (year round vs 3 months, 4x higher harvest/km 2 /year) would reduce relative abundance of hunted species and result in a larger fear-based response to humans (i.e., more spatial and temporal avoidance). We further evaluated how changes in animal abundance and behavior would result in potential changes to ecological impacts (i.e., herbivory and predation). We found that hunted species were relatively less abundant in Germany and less associated with humans on the landscape (i.e., yards and urban areas), but did not avoid humans temporally in hunted areas while hunted species in the USA showed the opposite pattern. These results are consistent with the risk allocation hypothesis where we would expect more spatial avoidance in response to threats of longer duration (i.e., year-round hunting in Germany vs. 3-month duration in USA) and less spatial avoidance but more temporal avoidance for threats of shorter duration. The expected ecological impacts of mammals in all three habitats were quite different between countries, most strikingly due to the decreases in the relative abundance of hunted species in Germany, particularly deer, with no proportional increase in unhunted species, resulting in American yards facing the potential for 25x more herbivory than German yards. Our results suggest that the duration and intensity of managed hunting can have strong and predictable effects on animal abundance and behavior, with the potential for corresponding changes in the ecological impacts of wildlife. Hunting can be an effective tool for reducing wildlife How to cite this article Parsons AW, Wikelski M, Keeves von Wolff B, Dodel J, Kays R. 2022. Intensive hunting changes human-wildlife relationships. PeerJ 10:e14159 http://doi.org/10.7717/peerj.14159 conflict due to overabundance but may require more intensive harvest than is seen in much of North America.
... 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. ...
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). ...
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). ...
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). ...
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.
... 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). ...
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.
... 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. ...
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.
... 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). ...
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.
... 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). ...
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.
Artificial light at night significantly alters the predictability of the natural light cycles that most animals use as an essential Zeitgeber for daily activity. Direct light has well-documented local impacts on activity patterns of diurnal and nocturnal organisms. However, artificial light at night also contributes to an indirect illumination of the night sky, called skyglow, which is rapidly increasing. The consequences of this wide-spread form of artificial night light on the behaviour of animals remain poorly understood, with only a few studies performed under controlled (laboratory) conditions. Using animal-borne activity loggers, we investigated daily and seasonal flight activity of a free-living crepuscular bird species in response to nocturnal light conditions at sites differing dramatically in exposure to skyglow. We find that flight activity of European Nightjars (Caprimulgus europaeus) during moonless periods of the night is four times higher in Belgium (high skyglow exposure) than in sub-tropical Africa and two times higher than in Mongolia (near-pristine skies). Moreover, clouds darken the sky under natural conditions, but skyglow can strongly increase local sky brightness on overcast nights. As a result, we find that nightjars' response to cloud cover is reversed between Belgium and sub-tropical Africa and between Belgium and Mongolia. This supports the hypothesis that cloudy nights reduce individual flight activity in a pristine environment, but increase it when the sky is artificially lit. Our study shows that in the absence of direct light pollution, anthropogenic changes in sky brightness relieve nightjars from visual constraints on being active. Individuals adapt daily activities to artificial night-sky brightness, allowing them more time to fly than conspecifics living under natural light cycles. This modification of the nocturnal timescape likely affects behavioural processes of most crepuscular and nocturnal species, but its implications for population dynamics and interspecific interactions remain to be investigated.
An early indication of changes in ecosystems can be noticed by the presence and behaviour of a few species that are highly sensitive to the change in the environment. Bird species are excellent indicators of changing ecosystems because they react fast to changes in their surroundings. Therefore, knowledge of all bird species and identifying their types are required to monitor the changing habitats and ecosystems. The performances of various pre-trained convolution neural networks (CNN) namely, MobileNet, MobileNetV2, NASNetMobile, and EfficientNets (version B0, B1, B2, B3, B4), in identifying Indian bird species using visual scene classification are evaluated in this study. As part of the Indian Bioresource Information Network (IBIN), this evaluation will aid in the development of Web/Mobile-Based Bird Species Identification Applications. The results indicate that EfficientNet B4 outperformed other architectures, however, the computational complexity is higher among all the selected CNN models. The EfficientNetB0 has demonstrated comparable performance with computational complexity comparable to MobileNet and NASNet and can be used in mobile platforms.
Light availability is one of the key drivers of animal activity, and moonlight is the brightest source of natural light at night. Moon phase is commonly used but, while convenient, it can be a poor proxy for lunar illumination on the ground. While the moon phase remains effectively constant within a night, actual moonlight intensity is affected by multiple factors such as disc brightness, position of the moon, distance to the moon, angle of incidence, and cloud cover. A moonlight illumination model is presented for any given time and location, which is significantly better at predicting lunar illumination than moon phase. The model explains up to 92.2% of the variation in illumination levels with a residual standard error of 1.4%, compared to 60% explained by moon phase with a residual standard error of 22.6%. Importantly, the model not only predicts changes in mean illumination between nights but also within each night, providing greater temporal resolution of illumination estimates. An R package moonlit facilitating moonlight illumination modelling is also presented. Using a case study, it is shown that modelled moonlight intensity can be a better predictor of animal activity than moon phase. More importantly, complex patterns of activity are shown where animals focus their activity around certain illumination levels. This relationship could not be identified using moon phase alone. The model can be universally applied to a wide range of ecological and behavioural research, including existing datasets, allowing a better understanding of lunar illumination as an ecological resource.
Significance statement
Moon phase is often used to represent lunar illumination as an environmental niche, but it is a poor proxy for actual moonlight intensity on the ground. A model is therefore proposed to estimate lunar illumination for any given place and time. The model is shown to provide a significantly better prediction of empirically measured lunar illumination than moon phase. Importantly, it also has much higher temporal resolutions, allowing to not only detect selectiveness for light levels between nights but also within each night, which is not achievable with moon phase alone. This offers unprecedented opportunities to study complex activity patterns of nocturnal species using any time-stamped data (GPS trackers, camera traps, song meters, etc.). It can also be applied to historical datasets, as well as facilitate future research planning in a wide range of ecological and behavioural studies.
Research into predator-prey interactions has focused on the landscape of fear (LOF) and non-consumptive effects that result from prey responses. Prey behavior is influenced by predator presence and the location and quality of foraging resources in habitats. These areas have been fruitful, but the role of prey refuges has lagged. We investigated how refuge spatial distribution and quality influence prey behavior. To determine the role of the landscape of safety (LOS) in prey decision making, we altered spatial relationships between refuges, refuge quality, and predation threats in mesocosms. Mesocosms were constructed that prey only received predatory chemical cues. We employed a behavioral assay including largemouth bass (Micropterus salmoides (Lacepède, 1802): predator) and virile crayfish (Faxonius rusticus (Girard 1852): prey). Crayfish shelter use was significantly influenced by quality and spatial relationship of shelters to predatory threats, and the interaction of these two factors. Particularly, crayfish used high-quality shelters more often when located closer to predatory cues than farther away and didn’t use low-quality shelters more than controls. High-quality shelter usage decreased as threat level (measured by gape ratio) decreased. These results support the idea that prey utilize a LOS, and information contained in these two landscapes may alter behavioral decisions.
The characteristics of animal distribution are determined by interactions between the resource requirements of animals and ecological factors. This study sought to evaluate the effects of diverse ecological factors on the home range and core area of red-backed voles (Myodes regulus) in a natural deciduous forest located on Mt. Gariwang, Pyeongchang and Jeongseon, South Korea. Our study focused on four types of ecological factors: topography, climate, cover, and demography. A total of 29 voles were radio-tracked from August to September 2021. Home range (95% utilization distribution; UD) and core area (50% UD) were calculated using the kernel density estimator (KDE). The home range (1659.49 m2) and core area (317.08 m2) were negatively affected by altitude. The lunar phase and temperature negatively and positively influenced the home range and core area, respectively. The home range was positively affected by understory vegetation, whereas the core area was not. The core area increased within microhabitats with a high density of conspecific individuals, with males having a larger home range (2006.19 m2) and core area (375.40 m2) than females (1043.13 m2 and 213.39 m2, respectively). These findings provide a deeper understanding of the diverse ecological factors affecting the distributions of animals, especially small rodents.
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.
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.
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.
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.
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’.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
In predator–prey theory, habitat heterogeneity can affect the relationship between kill rates and prey or predator density through its effect on the predator's ability to search for, encounter, kill and consume its prey. Many studies of predator–prey interactions include the effect of spatial heterogeneity, but these are mostly based on species with restricted mobility or conducted in experimental settings.
Here, we aim to identify the patterns through which spatial heterogeneity affects predator–prey dynamics and to review the literature on the effect of spatial heterogeneity on predator–prey interactions in terrestrial mammalian systems, i.e. in freely moving species with high mobility, in non‐experimental settings. We also review current methodologies that allow the study of the predation process within a spatial context.
When the functional response includes the effect of spatial heterogeneity, it usually takes the form of predator‐dependent or ratio‐dependent models and has wide applicability.
The analysis of the predation process through its different stages may further contribute towards identifying the spatial scale of interest and the specific spatial mechanism affecting predator–prey interactions.
Analyzing the predation process based on the functional response theory, but separating the stages of predation and applying a multiscale approach, is likely to increase our insight into how spatial heterogeneity affects predator–prey dynamics. This may increase our ability to forecast the consequences of landscape transformations on predator–prey dynamics.
Predators may influence their prey populations not only through direct lethal effects, but also through indirect behavioral changes. Here, we combined spatiotemporal fine-scale data from GPS radio collars on lions with habitat use information on 11 African herbivores in Hwange National Park (Zimbabwe) to test whether the risk of predation by lions influenced the distribution of herbivores in the landscape. Effects of long-term risk of predation (likelihood of lion presence calculated over four months) and short-term risk of predation (actual presence of lions in the vicinity in the preceding 24 hours) were contrasted. The long-term risk of predation by lions appeared to influence the distributions of all browsers across the landscape, but not of grazers. This result strongly suggests that browsers and grazers, which face different ecological constraints, are influenced at different spatial and temporal scales in the variation of the risk of predation by lions. The results also show that all herbivores tend to use more open habitats preferentially when lions are in their vicinity, probably an effective anti-predator behavior against such an ambush predator. Behaviorally induced effects of lions may therefore contribute significantly to structuring African herbivore communities, and hence possibly their effects on savanna ecosystems.