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Fire's impact on threat detection and risk perception among vervet monkeys: Implications for hominin evolution
Abstract
The spatial behavior of primates is shaped by many factors including predation risk, the distribution of food sources, and access to water. In fire-prone settings, burning is a catalyst of change, altering the distribution of both plants and animals. Recent research has shown that primates alter their behavior in response to this change. Here, we study primates' perceived threat of predation in fire-modified landscapes. We focus on the predator-related behaviors of vervet monkeys (Chlorocebus pygerythrus) after controlled burning events. We compare the occurrence of vigilance and predator-deterrent behaviors, including alarm calls, scanning, and flight across different habitats and burn conditions to test the hypothesis that subjects exhibit fewer predator-specific vigilance and predator-deterrent behaviors in burned areas. The results demonstrate that predator-related behaviors occur less often in burned habitats, suggesting that predators are less common in these areas. These results provide foundations for examining hypotheses about the use of fire-altered landscapes among extinct hominins. We set these data in the context of increasing aridity, changes in burning regimes, and the emergence of pyrophilia in the human lineage.
... While the interpretations we can make for vervet monkeys are more limited due to the low number of detections across our study, the relative abundance patterns observed leave open the possibility that vervet monkeys (~4 kg) may also have been able to largely evade the Cyclone Idai floodwaters through behavioral adjustments. In common with baboons, vervet monkeys are known to be highly adaptable as a species, surviving in harsh conditions and responding flexibly to change (Herzog et al. 2016(Herzog et al. , 2020Jaffe and Isbell 2009;McDougall et al. 2010;Pasternak et al. 2013;Wrangham 1981), such as adjusting their activity to spend more time resting at the expense of feeding to cope in extreme heat (McFarland et al. 2014) and exhibiting foraging flexibility in response to available food resources and the frequency of human interactions in urban environments (Thatcher, Downs, and Koyama 2020). Aside from our own species, baboons and vervet monkeys are the most widely distributed of the African primates, occupying a diverse range of habitats across the African continent (Wolfheim 1983). ...
Objectives
With contemporary, human‐induced climate change at a crisis point, extreme weather events (e.g., cyclones, heatwaves, floods) are becoming more frequent, intense, and difficult to predict. These events can wreak rapid and significant changes on ecosystems; thus, it is imperative to understand how wildlife communities respond to these disruptions. Primates are perceived as being a largely adaptable order, but we often lack the quantitative data to rigorously assess how they are impacted by extreme environmental change. Leveraging detections from a long‐term camera trap survey, this opportunistic study reports the effects of an extreme weather event on a little‐studied population of free‐ranging primates in Gorongosa National Park, Mozambique.
Materials and Methods
We examined shifts in gray‐footed chacma baboon ( Papio ursinus griseipes ) and vervet monkey ( Chlorocebus pygerythrus ) spatial distribution and relative abundance following Cyclone Idai—a category four tropical cyclone that struck Mozambique in March 2019.
Results
Baboon spatial distributions were impacted in the first month after the cyclone, with more detections in areas where flooding was less severe. Spatial distributions renormalized once floodwaters began to recede. We describe vervet monkey spatial distribution trends, though sample size limitations inhibited statistical analysis. Primate relative abundance did not appear to substantially decrease following the cyclone, suggesting troops were able to adopt behavioral adjustments to evade rising floodwaters.
Discussion
These findings highlight the behavioral flexibility of Gorongosa's primates and their ability to adapt to extreme—if temporary—disruptions, with implications for primate conservation in the Anthropocene and research into how rapid climatic events may have shaped primate evolution.
... Human groups living near the Fongoli study area report burning for safety (improving ability to detect dangerous animals and insects as well as to create firebreaks), accessibility and visibility, and to reduce parasite loads (Mbow et al., 2000). Similarly, Fongoli chimpanzees and other savanna-dwelling primates appear to find burned areas easier and possibly safer to move through (Jaffe and Isbell 2009;Pruetz and Herzog 2017;Herzog et al., 2020). Profitabilities, as reflected in patch residence times, do appear to be impacted by burning, but the relationships between rates of encounter and profitability are complex. ...
Humans' extensive use of fire is one behavior that sets us apart from all other animals. However, our ancestors' reliance on controlled forms of fire—i.e., for cooking—was likely preceded by a long familiarity with fire beginning with passive exploitation of naturally burned landscapes and followed by intermediate steps including active ecological modification via intentional burning. Here we explore our pyrophilic beginnings using observational data from savanna-dwelling chimpanzees. These data highlight the extent to which anthropogenic burning impacts the behavior and ecology of sympatric primates and provides an opportunity to study the ways in which apes living in a fire-altered world exploit opportunities presented by burning. Using monthly burn scar data and daily range use data we quantify the impact of burning episodes on chimpanzee habitat. Over the course of one dry season, approximately 74% of the total estimated range of the Fongoli community of savanna-dwelling chimpanzees (Pan troglodytes verus) was impacted by fire. We combine fire occurrences with behavioral data to test for relationships between burning and rate of encounter with food items and duration of subsequent patch residence time. Results show more frequent encounters and shorter patch residence times in burned areas. These data can be leveraged as a frame of reference for conceptualizing our extinct relatives’ behavior around fire.
... Another study on a different species of vervet monkey C. pygerythrus found that predatorrelated behaviours (e.g. vigilance, fleeing) rarely occurred in burnt areas, suggesting that monkeys feel safer there, perhaps due to increased visibility (Herzog et al., 2020). On the other hand, arboreal species that are less well adapted to moving along the ground may be particularly vulnerable after fires (Laurance, 2003). ...
Both fire and predators have strong influences on the population dynamics and behaviour of animals, and the effects of predators may either be strengthened or weakened by fire. However, knowledge of how fire drives or mediates predator-prey interactions is fragmented and has not been synthesised. Here, we review and synthesise knowledge of how fire influences predator and prey behaviour and interactions. We develop a conceptual model based on predator-prey theory and empirical examples to address four key questions: (i) how and why do predators respond to fire; (ii) how and why does prey vulnerability change post-fire; (iii) what mechanisms do prey use to reduce predation risk post-fire; and (iv) what are the outcomes of predator-fire interactions for prey populations? We then discuss these findings in the context of wildlife conservation and ecosystem management before outlining priorities for future research. Fire-induced changes in vegetation structure, resource availability, and animal behaviour influence predator-prey encounter rates, the amount of time prey are vulnerable during an encounter, and the conditional probability of prey death given an encounter. How a predator responds to fire depends on fire characteristics (e.g. season, severity), their hunting behaviour (ambush or pursuit predator), movement behaviour, territoriality, and intra-guild dynamics. Prey species that rely on habitat structure for avoiding predation often experience increased predation rates and lower survival in recently burnt areas. By contrast, some prey species benefit from the opening up of habitat after fire because it makes it easier to detect predators and to modify their behaviour appropriately. Reduced prey body condition after fire can increase predation risk either through impaired ability to escape predators, or increased need to forage in risky areas due to being energetically stressed. To reduce risk of predation in the post-fire environment, prey may change their habitat use, increase sheltering behaviour, change their movement behaviour, or use camouflage through cryptic colouring and background matching. Field experiments and population viability modelling show instances where fire either amplifies or does not amplify the impacts of predators on prey populations, and vice versa. In some instances, intense and sustained post-fire predation may lead to local extinctions of prey populations. Human disruption of fire regimes is impacting faunal communities, with consequences for predator and prey behaviour and population dynamics. Key areas for future research include: capturing data continuously before, during and after fires; teasing out the relative importance of changes in visibility and shelter availability in different contexts; documenting changes in acoustic and olfactory cues for both predators and prey; addressing taxonomic and geographic biases in the literature; and predicting and testing how changes in fire-regime characteristics reshape predator-prey interactions. Understanding and managing the consequences for predator-prey communities will be critical for effective ecosystem management and species conservation in this era of global change.
Recently, considerable attention has been paid to animal adaptations to anthropogenic environments, such as foraging in burned areas where plants are promoted to regenerate by anthropogenic burning. However, among primates, reports on the utilization of resources that are available immediately after burning have been limited to a few primate species. In this study, we investigated and compared the activity budgets and food categories of a group of patas monkeys (Erythrocebus patas) in freshly burned areas by comparing them with those in previously burned areas and unburned areas. We also assessed the proportion of time spent in the freshly burned area before and after the fire: GPS collars were fitted to five of the six adults in the group, and their patterns when they traveled toward freshly burned and unburned feeding areas were compared. Patas monkeys spent more time in freshly burned areas after the fire, and they visited such areas mostly for feeding, particularly on roasted seeds of Cissus populnea. Furthermore, patas monkeys traveled faster and in a more synchronized way toward freshly burned areas. This “apparent goal-directed” travel began at least 1 h before arriving. Results indicate that the group recognized freshly burned areas as valuable, and the monkeys were able to travel in a goal-directed manner to them despite their variable locations. We suggest that smoke from freshly burned areas provides a visual cue with which to orient to the burned areas. Our results also support the notion that some primates are flexible enough to adapt to and benefit from anthropogenic environmental changes.
Human musicality exhibits the necessary hallmarks for biological adaptations. Evolutionary explanations focus on recurrent adaptive problems that human musicality possibly solved in ancestral environments, such as mate selection and competition, social bonding/cohesion and social grooming, perceptual and motor skill development, conflict reduction, safe time-passing, transgenerational communication, mood regulation and synchronization, and credible signaling of coalition and territorial/predator defense. Although not mutually exclusive, these different hypotheses are still not conceptually integrated nor clearly derived from independent principles. I propose The Nocturnal Evolution of Human Musicality and Performativity Theory in which the night-time is the missing piece of the adaptationist puzzle of human musicality and performing arts. The expansion of nocturnal activities throughout human evolution, which is tied to tree-to-ground sleep transition and habitual use of fire, might help (i) explain the evolution of musicality from independent principles, (ii) explain various seemingly unrelated music features and functions, and (iii) integrate many ancestral adaptive values proposed. The expansion into the nocturnal niche posed recurrent ancestral adaptive challenges/opportunities: lack of luminosity, regrouping to cook before sleep, imminent dangerousness, low temperatures, peak tiredness, and concealment of identity. These crucial night-time features might have selected evening-oriented individuals who were prone to acoustic communication, more alert and imaginative, gregarious, risk-taking and novelty-seeking, prone to anxiety modulation, hedonistic, promiscuous, and disinhibited. Those night-time selected dispositions may have converged and enhanced protomusicality into human musicality by facilitating it to assume many survival- and reproduction-enhancing roles (social cohesion and coordination, signaling of coalitions, territorial defense, antipredatorial defense, knowledge transference, safe passage of time, children lullabies, and sexual selection) that are correspondent to the co-occurring night-time adaptive challenges/opportunities. The nocturnal dynamic may help explain musical features (sound, loudness, repetitiveness, call and response, song, elaboration/virtuosity, and duetting/chorusing). Across vertebrates, acoustic communication mostly occurs in nocturnal species. The eveningness chronotype is common among musicians and composers. Adolescents, who are the most evening-oriented humans, enjoy more music. Contemporary tribal nocturnal activities around the campfire involve eating, singing/dancing, storytelling, and rituals. I discuss the nocturnal integration of musicality’s many roles and conclude that musicality is probably a multifunctional mental adaptation that evolved along with the night-time adaptive landscape.
Humans have been using fire for hundreds of millennia, creating an ancestral expansion toward the nocturnal niche. The new adaptive challenges faced at night were recurrent enough to amplify existing psychological variation in our species. Night-time is dangerous and mysterious, so it selects for individuals with higher tendencies for paranoia, risk-taking, and sociability (because of security in numbers). During night-time, individuals are generally tired and show decreased self-control and increased impulsive behaviors. The lower visibility during night-time favors the partial concealment of identity and opens more opportunities for disinhibition of self-interested behaviors. Indeed, individuals with an evening-oriented chronotype are more paranoid, risk-taking, extraverted, impulsive, promiscuous, and have higher antisocial personality traits. However, under some circumstances, such as respiratory pandemics, the psychobehavioral traits favored by the nocturnal niche might be counter-productive, increasing contagion rates of a disease that can evade the behavioral immune system because its disease cues are often nonexistent or mild. The eveningness epidemiological liability hypothesis presented here suggests that during the COVID-19 pandemic, the evening-oriented psychobehavioral profile can have collectively harmful consequences: there is a clash of core tendencies between the nocturnal chronotype and the recent viral transmission-mitigating safety guidelines and rules. The pandemic safety protocols disrupt much normal social activity, particularly at night when making new social contacts is desired. The SARS-CoV-2 virus is contagious even in presymptomatic and asymptomatic individuals, which enables it to mostly evade our evolved contagious disease avoidance mechanisms. A growing body of research has indirectly shown that individual traits interfering with social distancing and anti-contagion measures are related to those of the nocturnal chronotype. Indeed, some of the social contexts that have been identified as superspreading events occur at night, such as in restaurants, bars, and nightclubs. Furthermore, nocturnal environmental conditions favor the survival of the SARS-CoV-2 virus much longer than daytime conditions. We compare the eveningness epidemiological liability hypothesis with other factors related to non-compliance with pandemic safety protocols, namely sex, age, and life history. Although there is not yet a direct link between the nocturnal chronotype and non-compliance with pandemic safety protocols, security measures and future empirical research should take this crucial evolutionary mismatch and adaptive metaproblem into account, and focus on how to avoid nocturnal individuals becoming superspreaders, offering secure alternatives for nocturnal social activities.
Both anecdotes and systematic observations show that primates take advantage of burned landscapes. However, few studies have made these behaviors the focus of attention. This dissertation includes three papers documenting the behavioral responses of South African vervet monkeys (Chlorocebus aethiops) to seasonal burning. The first paper details changes in spatial behavior related to burning. In it, we review the behavioral responses of other primate populations to fire, and describe typical ranging behavior among vervets. We compare our results to other accounts of primate-fire related behavior and evaluate whether the changes observed are unique to this population or species, or whether they are indicative of a primate-wide phenomenon. The second paper outlines changes in foraging opportunities postburn. Here, I compare the postencounter energetic returns and encounter rates of primate prey items within burned and unburned conditions. I identify improvements where they exist, and explore the hypothesis that burned savanna habitats offer improved foraging returns. Finally, the third chapter explores how and why fire alters both the threat of predation and general risk. I review the general pattern of predation on primates, and investigate the tradeoffs involved in risk avoidance. I conclude that burning offers savanna-dwelling primates a safe-haven from many primary predators and threats. I end the dissertation with a fourth paper that employs conceptual tools from optimal foraging theory to generate, test, and refine expectations about the behavioral adaptations of hominins inhabiting fire-prone savanna biomes. Here, I use the primate data to construct a general theory of behavior for the origins of human fire use. I argue that the behavior of savanna-dwelling primates may serve as a basis for hypotheses regarding the origins of fire use in the hominin lineage. I highlight the distinction between passive and active fire use, and use these observations to suggest future realms of research investigating fire-related behavioral shifts and their effect on the human life history, hominin dispersals, and the adaptation of complex pyrotechnology.
Knowledge of how disturbances such as fire shape habitat structure and composition, and affect animal interactions, is fundamental to ecology and ecosystem management. Predators also exert strong effects on ecological communities, through top‐down regulation of prey and competitors, which can result in trophic cascades. Despite their ubiquity, ecological importance and potential to interact with fire, our general understanding of how predators respond to fire remains poor, hampering ecosystem management.
To address this important knowledge gap, we conducted a systematic review and meta‐analysis of the effects of fire on terrestrial, vertebrate predators world‐wide. We found 160 studies spanning 1978–2018. There were 36 studies with sufficient information for meta‐analysis, from which we extracted 96 effect sizes (Hedges' g) for 67 predator species relating to changes in abundance indices, occupancy or resource selection in burned and unburned areas, or before and after fire.
Studies spanned geographic locations, taxonomic families and study designs, but most were located in North America and Oceania (59% and 24%, respectively), and largely focussed on felids (24%) and canids (25%). Half (50%) of the studies reported responses to wildfire, and nearly one third concerned prescribed (management) fires.
There were no clear, general responses of predators to fire, nor relationships with geographic area, biome or life‐history traits (e.g. body mass, hunting strategy and diet). Responses varied considerably between species. Analysis of species for which at least three effect sizes had been reported in the literature revealed that red foxes Vulpes vulpes mostly responded positively to fire (e.g. higher abundance in burned compared to unburned areas) and eastern racers Coluber constrictor negatively, with variances overlapping zero only slightly for both species.
Our systematic review and meta‐analysis revealed strong variation in predator responses to fire, and major geographic and taxonomic knowledge gaps. Varied responses of predator species to fire likely depend on ecosystem context. Consistent reporting of ongoing monitoring and management experiments is required to improve understanding of the mechanisms driving predator responses to fire, and any broader effects (e.g. trophic interactions). The divergent responses of species in our study suggest that adaptive, context‐specific management of predator–fire relationships is required.
Significance
Fire is crucial to maintaining modern subtropical grasslands, yet the geologic and ecological history of this association is not well constrained. Here, we test the role of fire during the expansion of C 4 grassland ecosystems in the Mio-Pliocene through innovative molecular proxies from ancient soils in Pakistan. We produce a synoptic terrestrial record of fire and vegetation change in this region, which indicates that increased fire occurrence accompanied two stages of landscape opening. Proxy data confirm that a pronounced fire–grassland feedback was a critical component of grassland ecosystems since their origination and fostered the rise of C 4 -dominated grasslands. The approach presented here can be used to examine landscape-scale interactions between paleofire and vegetation for other geographic regions and climatic transitions.
Vigilance functions to detect threats. In primates, these threats emerge from both predators and conspecifics, but a host of other social, demographic, and ecological factors have been shown to influence primate vigilance patterns. The primate vigilance literature is thus characterized by considerable variation in findings, with inconsistent or contradictory results reported not only across different species but also within species and populations across studies. Some of this variation could emerge from fundamental differences in the methods employed, making comparisons across species and groups challenging. Furthermore, identifying consistent behavioral markers for the state of vigilance appears to have proved challenging in primates, leading to a range of definitions being developed. Deviation at this level leads directly into concomitant variation at the level of sampling methodologies. As a result, the primate vigilance literature currently presents a diverse series of approaches to exploring subtly different behaviors and phenomena. This review calls for a greater consistency in studying vigilance, with the aim of encouraging future research to follow similar principles leading to more comparable results. Identifying whether an animal is in a vigilant state is challenging for most field researchers; identifying and recording a more general behavior of “looking” should though be more achievable. Experimental approaches could then be employed to understand the compatibility “looking” has with predator detection (and other threats) in individual study systems. The outcome of this approach will allow researchers to understand the key determinants of looking in their study groups and explore threat detection probabilities given an individual or group's relative level of looking.
Both short-term and long-term variation in predation risk can affect the behaviour of prey, thus affecting growth, reproduction, survival and population dynamics. Inferences about the strength of such ‘risk effects’ in the wild have been limited by a lack of studies that relate antipredator responses to the magnitude of direct predation, measure responses of prey to risk from complete predator guilds, and quantify risk in more than one way. Here, we quantify behavioural responses of a complete ungulate prey guild to long-term and short-term variation in risks from all of the large predators in Liuwa Plain National Park, with known patterns of direct predation. Our analysis allows the first direct test for interaction between responses to long-term and short-term risk in the wild, and reveals that prey vigilance responds strongly to locations with high long-term risk when short-term risk is high, but not when short-term risk is low. This result has broad ramifications for the design and interpretation of field studies of antipredator behaviour, its costs and its consequences for population dynamics.
Savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal, appear to be able to predict the “behavior” of wildfires of various intensities. Although most wildfires are avoided, even the most intense fires are met with relative calm and seemingly calculated movement by apes in this arid, hot, and open environment. In addition to reviewing instances of such behavior collected during the course of the Fongoli study, we also report chimpanzees’ use of burned landscapes during the dry season, when more than 75% of these apes’ home range may be burned annually. In burned areas, chimpanzees spent more time foraging and traveling than in unburned areas. Chimpanzees’ behavior in a fire context can help inform paleoanthropological hypotheses regarding early members of our own lineage and can provide insight into the ability of early hominins to conceptualize the behavior of fire and thus set the stage for our lineage’s use of fire.
Behavioural predator–prey interactions are difficult to study, especially when predators avoid humans. To gain greater understanding of their dynamism, we conducted a 14-month field study in which we minimized human presence by employing acoustic recorders and camera traps, along with GPS collars deployed on vervet monkeys (Chlorocebus pygerythrus) and leopards (Panthera pardus) in Laikipia, Kenya. Recordings at the vervets’ sleeping site revealed that they gave ‘leopard’ alarm calls most frequently near dusk and dawn, whereas photographs showed that leopards approached vervets more closely at night, when the monkeys alarm-called less often. GPS data showed that after vervets alarm-called, leopards within 200 m quickly moved away, changing direction, but when vervets did not alarm-call, leopards continued moving forward. These results reveal that vervets’ leopard alarm calls function as a predator deterrent in addition to a conspecific warning call.
Members of genus Homo are the only animals known to create and control fire. The adaptive significance of this unique behavior is broadly recognized, but the steps by which our ancestors evolved pyrotechnic abilities remain unknown. Many hypotheses attempting to answer this question attribute hominin fire to serendipitous, even accidental, discovery. Using recent paleoenvironmental reconstructions, we present an alternative scenario in which, 2 to 3 million years ago in tropical Africa, human fire dependence was the result of adapting to progressively fire-prone environments. The extreme and rapid fluctuations between closed canopy forests, woodland, and grasslands that occurred in tropical Africa during that time, in conjunction with reductions in atmospheric carbon dioxide levels, changed the fire regime of the region, increasing the occurrence of natural fires. We use models from optimal foraging theory to hypothesize benefits that this fire-altered landscape provided to ancestral hominins and link these benefits to steps that transformed our ancestors into a genus of active pyrophiles whose dependence on fire for survival contributed to its rapid expansion out of Africa.
A study was undertaken of a unique sample of 63 wild vervet monkeys Cercopithecus aethiops from a single population in Uganda collected over 35 days in 1947. Twenty-five were immature (12 females and 13 males) and 38 were adults (16 females and 22 males). Body mass, external measurements, masticatory and other masses were recorded for each individual at the time of collection, and for a few specimens, the development of the reproductive organs. Each individual was evaluated for cranial capacity, limb length and dental eruption. The comparison of immature and adult animals illustrates the mosaic nature of growth in the different body systems, as well as female-male differences. An ancestral model is proposed for catarrhine growth and development, with particular reference to sex differences. This model provides a framework for assessment of immatures and for the reconstruction of socio-ecological effects on life-history stages in populations of fossil monkeys, apes and early hominids.
Carnivores play a central role in ecosystem processes by exerting top-down control, while fire exerts bottom-up control in ecosystems throughout the world, yet, little is known about how fire affects short-term carnivore distributions across the landscape. Through the use of a long-term data set we investigated the distribution of lions, during the daytime, in relation to burned areas in Serengeti National Park, Tanzania. We found that lions avoid burned areas despite the fact that herbivores, their prey, are attracted to burned areas. Prey attraction, however, likely results from the reduction in cover caused by burning, that may thereby decrease lion hunting success. Lions also do not preferentially utilize the edges of burned areas over unburned areas despite the possibility that edges would combine the benefit of cover with proximity to abundant prey. Despite the fact that lions avoid burned areas, lion territory size and reproductive success were not affected by the proportion of the territory burned each year. Therefore, burning does not seem to reduce lion fitness perhaps because of the heterogeneity of burned areas across the landscape or because it is possible that when hunting at night lions visit burned areas despite their daytime avoidance of these areas.
Animal Vigilance builds on the author's previous publication with Academic Press (Social Predation: How Group Living Benefits Predators and Prey) by developing several other themes including the development and mechanisms underlying vigilance, as well as developing more fully the evolution and function of vigilance. Animal vigilance has been at the forefront of research on animal behavior for many years, but no comprehensive review of this topic has existed. Students of animal behavior have focused on many aspects of animal vigilance, from models of its adaptive value to empirical research in the laboratory and in the field. The vast literature on vigilance is widely dispersed with often little contact between models and empirical work and between researchers focusing on different taxa such as birds and mammals. Animal Vigilance fills this gap in the available material..
Objectives:
Anecdotal and formal evidence indicate that primates take advantage of burned landscapes. However, little work has been done to quantify the costs and benefits of this behavior. Using systematic behavioral observations from a population of South African vervet monkeys (Chlorocebus aethiops pygerythrus), we evaluate differences in food availability and energetics before and after controlled burns altered vegetation near their home range. We aim to determine whether burned habitats offer improved foraging opportunities.
Methods:
We collected feeding data from foraging individuals and analyzed common plant foods for their energetic content. We then used the feeding and energetic data to calculate postencounter profitabilities and encounter rates for food types. Using negative binomial and mixed linear regression models we compared data from burned and unburned habitats.
Results:
Our results show significantly improved encounter rates in burned landscapes for two prey items, invertebrates and grasses. However, postencounter profitabilities in burned areas were not significantly different than those achieved in unburned areas.
Conclusions:
Results suggest that improved encounters alone can motivate changes in foraging behavior. These foraging benefits enable the exploitation of burned savanna habitats, likely driving postburn range expansions observed among populations of vervet monkeys. Thus quantified, these results may serve as a foundation for hypotheses regarding the evolution of fire-use in our own lineage. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.
The alarm calls of vervet monkeys (Chlorocebus pygerythrus) constitute the classic textbook example of semantic communication in nonhuman animals, as vervet monkeys give acoustically distinct calls to different predators and these calls elicit appropriate responses in conspecifics. They also give similar sounding calls in aggressive contexts, however. Despite the central role the vervet alarm calls have played for understanding the evolution of communication, a comprehensive, quantitative analysis of the acoustic structure of these calls was lacking. We used 2-step cluster analysis to identify objective call types and discriminant function analysis to assess context specificity. Alarm calls given in response to leopards, eagles, and snakes could be well distinguished, while the inclusion of calls given in aggressive contexts yielded some overlap, specifically between female calls given to snakes, eagles and during aggression, as well as between male vervet barks (additionally recorded in South Africa) in leopard and aggressive contexts. We suggest that both cognitive appraisal of the situation and internal state contribute to the variation in call usage and structure. While the semantic properties of vervet alarm calls bear little resemblance to human words, the existing acoustic variation, possibly together with additional contextual information, allows listeners to select appropriate responses.
For anthropologists, meat eating by primates like chimpanzees (Pan troglodytes) warrants examination given the emphasis on hunting in human evolutionary history. As referential models, apes provide insight into the evolution of hominin hunting, given their phylogenetic relatedness and challenges reconstructing extinct hominin behaviour from palaeoanthropological evidence. Among chimpanzees, adult males are usually the main hunters, capturing vertebrate prey by hand. Savannah chimpanzees (P. t. verus) at Fongoli, Sénégal are the only known non-human population that systematically hunts vertebrate prey with tools, making them an important source for hypotheses of early hominin behaviour based on analogy. Here, we test the hypothesis that sex and age patterns in tool-assisted hunting (n = 308 cases) at Fongoli occur and differ from chimpanzees elsewhere, and we compare tool-assisted hunting to the overall hunting pattern. Males accounted for 70% of all captures but hunted with tools less than expected based on their representation on hunting days. Females accounted for most tool-assisted hunting. We propose that social tolerance at Fongoli,
The estimation of body size among the earliest members of the genus Homo (2.4–1.5Myr [millions of years ago]) is central to interpretations of their biology. It is widely accepted that Homo ergaster possessed increased body size compared with Homo habilis and Homo rudolfensis, and that this may have been a factor involved with the dispersal of Homo out of Africa. The study of taxonomic differences in body size, however, is problematic. Postcranial remains are rarely associated with craniodental fossils, and taxonomic attributions frequently rest upon the size of skeletal elements. Previous body size estimates have been based upon well-preserved specimens with a more reliable species assessment. Since these samples are small (n < 5) and disparate in space and time, little is known about geographical and chronological variation in body size within early Homo.
Prescribed fire is an important management tool in east Africa as a way to improve foraging conditions for herbivores, and to make wildlife easier for tourists to observe and photograph. Although past research has investigated the factors influencing herbivore use of post-fire vegetation, the temporal dynamics of these effects have seldom been documented, and use of burned areas by African carnivores has not been evaluated. Between 2008 and 2011, we studied responses of 8 common herbivores and 8 carnivore species to burns in the Mara-Serengeti ecosystem in southwestern Kenya by monitoring mammal abundance on 4 transects from up to 136 days before burning, and up to 748 days after burning. Among herbivores, zebra, warthog, Thomson's gazelle, Grant's gazelle, and topi, occurred in higher densities in burned than unburned areas. Impala and wildebeest showed trends toward occurring in higher densities in burned areas. These effects lasted up to 120 days for Thomson's gazelle, but we did not observe a specific temporal relationship to burning in the other 5 herbivore species. Both small and large carnivores were more likely to be observed along transects after than before burns; we observed small carnivores including black-backed jackals, side-striped jackals, bat-eared foxes, and banded mongoose in greater numbers up to 365 days after burns but observed large carnivores, including African lions, spotted hyenas, leopards, and cheetahs, in greater numbers only for up to 120 days after burns. Our results indicate that wildlife responses to prescribed fire last ≤1 year in this region. Although burning stimulates vegetation growth and improves wildlife visibility, managers should recognize that wildlife responses might not persist for more than a few months in tropical African savannas like the one monitored here. © 2014 The Wildlife Society.
Humans and human infrastructure are known to alter the relationship between predators and prey, typically by directly or indirectly shielding one of the species from the other. In addition to these overt changes to animals’ behavior, observers may have more subtle impacts on animals’ foraging decisions. However, the anthropogenic alteration of risk-taking behavior has rarely been acknowledged or quantified, particularly in behavioral ecological studies reliant on habituated animals. We tested the magnitude of the “human shield
effect” experimentally on 2 groups of samango monkeys, Cercopithecus mitis erythrarcus, at a site with high natural predator density and no human hunting pressure. In general, giving-up densities—the density of food remaining in a patch when a forager leaves—were greatest at ground level (0.1 m) relative to 3 tree canopy levels (2.5, 5, and 7.5 m), highlighting a strong vertical axis of fear. When human followers were present, however, giving-up densities were reduced at all 4 heights; furthermore, for 1 group, the vertical axis
disappeared in the presence of observers. Our results suggest that human observers lower monkeys’ perceived risk of terrestrial predators and, thereby, affect their foraging decisions at or near ground level. These results have significant implications for future studies of responses to predation risk based on habituation and observational methods.
The behavioral adaptations of primates to fire-modified landscapes are of considerable interest to anthropologists because fire is fundamental to life in the African savanna-the setting in which genus Homo evolved. Here we report the behavioral responses of a savanna-dwelling primate, vervet monkeys (Chlorocebus aethiops), to fire-induced ecological change. Using behavioral and spatial data to characterize ranging patterns prior to and postburn and between burn and nonburn years, we show that these primates inhabiting small, spatially bound, riverine habitats take advantage of newly burned savanna landscapes. When subjects encountered controlled fires, they did not flee but instead avoided the path of the fire seemingly unbothered by its approach. After fire, the primates' home range expanded into newly burned but previously unused areas. These results contribute to understanding the response of non-human primates to fire-modified landscapes and can shed light on the nature and scope of opportunities and constraints posed by the emergence of fire-affected landscapes in the past. Results also expose deficiencies in our knowledge of fire-related behavioral responses in the primate lineage and highlight the need for further investigation of these responses as they relate to foraging opportunities, migration, resource use, and especially fire-centric adaptations in our own genus. Am J Phys Anthropol, 2014. © 2014 Wiley Periodicals, Inc.
One of the most important factors influencing the foraging of animals is predation risk. As a result, animals do not utilize landscapes uniformly. Vervet monkeys (Chlorocebus aethiops) use both arboreal and terrestrial habitats, and thus forage across a 3-dimensional landscape. To explore how both aerial and terrestrial predators influenced small-scale foraging patterns, we measured giving-up densities (GUDs) in artificial food patches across a woodland-grassland interface. Patch transects ran vertically through trees, and horizontally into open grasslands. As vervets move up trees to avoid terrestrial predators and down out of the canopies to avoid aerial predators, we predicted that there would be a safe zone with higher patch use extending from just below the canopy to the base of the tree. Lower GUDs in this area showed this to be the case. Another factor that influenced patch use was group size. The different sized groups displayed a similar overall pattern of patch selection (i.e., they all fed more in specific patches). However, larger groups fed more intensively in all patches. As a result, larger groups achieved lower GUDs in all patches compared to the smaller groups both vertically and horizontally. Possible explanations include differences in predator abundance between the locations of the groups, group benefits lowering prédation risk, competition forcing individuals to feed in less safe patches, or a combination of these factors. Ultimately, our results indicate that prédation risk from both aerial and terrestrial predators shapes the vervets' 3-dimensional landscape of fear.
The global diversity of human languages is a remarkable feature of our species, which requires a capacity for rapid vocal learning. Given that primate alarm calling systems have played an important role in the language origin debate, identifying geographic variation in primate alarm calls and understanding the underlying causal mechanisms are important steps to help uncover evolutionary precursors to language. This study investigates geographic variation in the alarm bark of the widely distributed African green monkey (Chlorocebus). To quantify geographic variation in spectral and temporal call structure, acoustic analysis was used to compare the adult male barks of green monkeys (Chlorocebus sabaeus) and two subspecies of vervet (Chlorocebus pygerythrus pygerythrus and Chlorocebus pygerythrus hilgerti). Playback experiments were also carried out to test whether adult male vervets would distinguish between the barks of own-group males, unknown conspecific males and green monkey males. Acoustic analysis showed that, whilst similar in overall structure, the barks of green monkeys could be distinguished from vervet barks with a high degree of accuracy; the barks of vervet subspecies could also be discriminated, although to a lesser degree. Males responded most strongly to unknown conspecific males’ barks, and exhibited responses typical of leopard-avoidance and territorial defence. Taken together, these findings indicate that variation in alarm calls can be best explained by phylogenetic distance, and that intra- and inter-species differences are relevant during social interactions. Moreover, barks may function as an alarm and display call, which could explain the observed sexual dimorphism in barks in this genus.
Electronic supplementary material
The online version of this article (doi:10.1007/s00265-014-1694-y) contains supplementary material, which is available to authorized users.
Carnivores that persist outside of protected areas are often deemed to have highly adaptable and generalist foraging strategies. Using data from three GPS-collared female leopards (Panthera pardus) and over an eight-month period, we attempted to establish whether leopards in a mountainous landscape display preferential behaviour (i.e. specialist) or not (i.e. generalist). We investigated whether female leopards used habitats in accordance with availability for both hunting and regular activities, and whether female leopards demonstrated preference for a particular prey species. Finally, we assessed tree caching behaviour and discuss leopard spatial dynamics in the context of superior competitors, such as lions (Panthera leo). Female leopards demonstrated selection for certain prey species. Mixed closed woodland (greatest vegetation density; lowest prey density) and tall open woodland (greatest vegetation biomass; high prey density) were preferred over other habitats. Female leopards on Welgevonden cached significantly larger prey species in trees. Our results suggest that female leopards in this landscape are selecting habitats - enabling the exploitation of certain ecological features - that balance energy expenditure against the likelihood of capturing prey in an attempt to maximize efficiency, whilst reducing inter-specific competition. We suggest that female leopards are limited in their foraging ability as a result of interference competition by superior species like lions, which in turn, affects their choice of prey. These findings highlight the potential importance of numerous ecological, spatio-temporal, and anthropogenic factors that influence leopard behaviour, and therefore have significant implications for leopard persistence and conservation.
Foraging in burned areas has been suggested to represent the earliest stage in the use and control of fire by early hominins. Recently burned areas offer immediate foraging benefits including increased search efficiency for high‐ranked food items and decreased hunting opportunities for ambush predators. As such, they provide a triple‐bonus (reduced risk from ambush, ease of terrestrial travel and higher foraging returns) for some primates. However, previous studies have not yet accounted for other types of predators e.g., coursing (endurance predators that can pursue prey over long distances) which were sympatric with hominins and may also have exploited these environments. Behavioral ecology studies on the use of burned landscapes by extant carnivores demonstrate that while some ambush predators avoid recently burned areas, coursing predators do take advantage of their immediate hunting opportunities. Research examining habitat selection by animals under the simultaneous threat of multiple predator species with different modes of hunting, and the diversity of Plio‐Pleistocene carnivore guild is suggestive of two possible evolutionary scenarios in which hominins could either have selected or avoided burned areas (3–2 mya), based on whether ambush or coursing predators were perceived as presenting the greatest risk.
Significance
Testing ecological hypotheses of human evolution requires an understanding of the ancient plant and animal communities within which our ancestors lived. Though present-day ecosystems provide the baseline for reconstructing the ecological context of human evolution, the extent to which modern ecosystems are representative of past ones is unknown. Through analyses of a fossil dataset spanning the last 7 Myr, we show that eastern African communities of large-bodied mammalian herbivores differed markedly from those today until ∼700,000 y ago. Because large herbivores are ecosystem engineers and shape biotic communities in ways that impact a wide variety of species, this implies that the vast majority of early human evolution transpired in the context of ecosystems that functioned unlike any known today.
Large carnivores can exert strong influence on local ecosystems, making them important targets for biodiversity conservation. An important question for conserving large carnivores outside of protected areas is the role of human activity in influencing the behavior of these predators. We used high-resolution animal location tracking and statistical modeling to examine the behavior of seven leopards (Panthera pardus) occupying an area that includes a research center and livestock ranch in central Kenya. Our analyses reveal changes in habitat selection around the times of sunrise and sunset, corresponding with changes in human activity at our site. Activity patterns were also variable within and among the leopards in our sample. To explore sources of this variability, we used regression modeling to estimate the relative influence of changing spatial and environmental conditions for leopard ranging behavior. Despite the tendency to be active during the day, we found that leopards strongly avoided areas where they were likely to encounter people during the daytime and showed variable selection for these same areas at night. The use of anthropogenic habitats was also associated with periods of greater ranging activity. We discuss the implications of these results for conservation efforts that attempt to balance the demands of livestock ranching alongside carnivore conservation.
Man the Hunted argues that primates, including the earliest members of the human family, have evolved as the prey of any number of predators, including wild cats and dogs, hyenas, snakes, crocodiles, and even birds. The authors’ studies of predators on monkeys and apes are supplemented here with the observations of naturalists in the field and revealing interpretations of the fossil record. Eyewitness accounts of the ‘man the hunted’ drama being played out even now give vivid evidence of its prehistoric significance. This provocative view of human evolution suggests that countless adaptations that have allowed our species to survive (from larger brains to speech), stem from a considerably more vulnerable position on the food chain than we might like to imagine. The myth of early humans as fearless hunters dominating the earth obscures our origins as just one of many species that had to be cautious, depend on other group members, communicate danger, and come to terms with being merely one cog in the complex cycle of life.
There is over 60 years of discussion in the statistical literature concerning the misuse and limitations of null hypothesis significance tests (NHST). Based on the prevalence of NHST in biological anthropology research, it appears that the discipline generally is unaware of these concerns. The p values used in NHST usually are interpreted incorrectly. A p value indicates the probability of the data given the null hypothesis. It should not be interpreted as the probability that the null hypothesis is true or as evidence for or against any specific alternative to the null hypothesis. P values are a function of both the sample size and the effect size, and therefore do not indicate whether the effect observed in the study is important, large, or small. P values have poor replicability in repeated experiments. The distribution of p values is continuous and varies from 0 to 1.0. The use of a cut-off, generally p ≤ 0.05, to separate significant from nonsignificant results, is an arbitrary dichotomization of continuous variation. In 2016, the American Statistical Association issued a statement of principles regarding the misinterpretation of NHST, the first time it has done so regarding a specific statistical procedure in its 180-year history. Effect sizes and confidence intervals, which can be calculated for any data used to calculate p values, provide more and better information about tested hypotheses than p values and NHST.
Predators affect prey by killing them directly (lethal effects) and by inducing costly antipredator behaviours in living prey (risk effects). Risk effects can strongly influence prey populations and cascade through trophic systems. A prerequisite for assessing risk effects is characterizing the spatiotemporal variation in predation risk.
Risk effects research has experienced rapid growth in the last several decades. However, preliminary assessments of the resultant literature suggest that researchers characterize predation risk using a variety of techniques. The implications of this methodological variation for inference and comparability among studies have not been well recognized or formally synthesized.
We couple a literature survey with a hierarchical framework, developed from established theory, to quantify the methodological variation in characterizing risk using carnivore–ungulate systems as a case study. Via this process, we documented 244 metrics of risk from 141 studies falling into at least 13 distinct subcategories within three broader categories.
Both empirical and theoretical work suggest risk and its effects on prey constitute a complex, multi‐dimensional process with expressions varying by spatiotemporal scale. Our survey suggests this multi‐scale complexity is reflected in the literature as a whole but often underappreciated in any given study, which complicates comparability among studies and leads to an overemphasis on documenting the presence of risk effects rather than their mechanisms or scale of influence.
We suggest risk metrics be placed in a more concrete conceptual framework to clarify inference surrounding risk effects and their cascading effects throughout ecosystems. We recommend studies (i) take a multi‐scale approach to characterizing risk; (ii) explicitly consider ‘true’ predation risk (probability of predation per unit time); and (iii) use risk metrics that facilitate comparison among studies and the evaluation of multiple competing hypotheses. Addressing the pressing questions in risk effects research, including how, to what extent and on what scale they occur, requires leveraging the advantages of the many methods available to characterize risk while minimizing the confusion caused by variability in their application.
This chapter summarizes the ways in which habitat structure affects perceived risk of predation and responses to predators
(i.e., anti-predator behavior) by cercopithecines (Superfamily: Cercopithecoidea), with specific reference to vervet (Cercopithecus aethiops) and patas (Erythrocebus patas) monkeys. Predation has long been thought to be an important selective pressure on primate behavior and sociality (e.g.,
Altmann, 1974; Busse, 1977; Struhsaker, 1981; van Schaik, 1983; Cheney & Wrangham, 1987; Cords, 1987; Isbell, 1991, 1994; Miller, 2002). Among Old World monkeys, predation has been argued to have favored traits such as large group size (e.g., van Schaik, 1983), multi-male groups (e.g., Henzi, 1988; van Schaik & Hörstermann, 1994), sexual dimorphism in canine size (e.g., Harvey & Kavanagh, 1978; Plavcan & van Schaik, 1994), and polyspecific associations (e.g., Gautier-Hion et al., 1983; Cords, 1987; Struhsaker, 1981, 2000), although others maintain that these traits have been selected for by feeding competition (Wrangham, 1980, 1983; Janson & Goldsmith, 1995), sexual selection (Andelman, 1986; Ridley, 1986; Altmann, 1990; Mitani et al., 1996), or, most recently, infanticide (van Schaik & Kappeler, 1997; Isbell et al., 2002).
The extent to which animal vocalizations convey specific information about events in the environment is subject to continued debate. The alarm-calls of vervet monkeys have played a pivotal role in this debate as they represent the classic example of a predator-specific call production system combined with a set of equally specific responses by receivers. Here, we revisit the vervet alarm-calling system, and assess the hypothesis that these acoustically distinct calls trigger context- and predator-appropriate behavior. We investigated responses in 2 groups of free-ranging vervet monkeys (Chlorocebus pygerythrus) to both natural encounters with predators and experimental presentations of aerial and terrestrial predator alarm calls. Our results show that the modal natural and experimental response was not to initiate escape behavior, either immediately or in the 10s following an alarm call, but to look at the sound source. When monkeys did take evasive action, contextually inappropriate behavior (i.e., behavior that was not appropriate for evading the specific predator type) was as likely to occur as contextually appropriate behavior. The distance at which calls were heard was negatively correlated with the probability of evasive action. Larger group size, and the greater mean distance at which natural calls were heard, may explain why our animals displayed less predator-appropriate evasion or vigilance than expected. We conclude that the broader social and ecological framework in which calls occur, rather than a simple contextually regular linkage between call types and specific predators, shapes animals' responses to calls in this species. © 2014 International Society for Behavioral Ecology. All rights reserved.
This study investigates the relative importance of vigilance in the survival strategies (detection of predators) and reproductive strategies (detection of mates and competitors) of adult baboons Papio cynocephalus ursinus among four groups in a desert population. The proportion of time spent vigilant under a variety of conditions was quantified through instantaneous sampling of focal individuals. Matched comparisons were then conducted to test six predictions for each functional explanation (survival or reproduction). These relate vigilance to (1) sex, (2) group size, (3) activity, (4) habitat, (5) refuge use and (6) spacing behaviour. Vigilance levels do not differ between sexes or groups. However, females are more vigilant when engaged in high-risk activities, when distant from refuges and when distant from neighbours. Male vigilance similarly covaries with refuge use and spacing behaviour, but males are not always more vigilant in dangerous activities and show greater vigilance in open rather than closed habitats. According to the predictions tested, the results provide partial support for the proposal that vigilance plays a role in predator detection for both sexes, although in males the detection of potential mates and competitors appears to be of greater importance. There was no evidence that males provide a vigilance service for females. Vigilance patterns are complicated by activity constraints and the multifactorial nature of anti-predator strategies.
It is suggested that predation, initially upon early hominids by more powerful carnivores, but latterly by humans on their hunted prey, served as a powerful stimulus for the evolution of intelligence. Predation, as a way of life, can be traced back to the earliest animals, over 500 million years ago. It appears that, from the beginning of the animal heterotrophic tradition, predation has promoted the development of the sensory/nervous systems, both for the purposes of catching prey and of evading predators.
Aspects of the ecology of vervet monkeys (Ceropithecus aethiops) are described on the basis of a 21 month field study in East Africa. Analysis of home range utilization demonstrated differences between 4 groups. The smallest group distributed its time over a greater area than did the other groups. For 3 of the groups there appeared to be a strong relationship between group size and the amount of optimal habitat defended. The smallest group defended more optimal habitat than expected. However, this same group spent only 60% of its time in this habitat, whereas the other groups all spent more than 95% of their time in it. The smallest group may have avoided the optimal habitat of its territory as an area of frequent intergroup aggression, and as a result utilized a larger and less productive area. Sleeping-tree preferences of groups and individuals are described and discussed. The minimal distance traveled each day by vervet groups varied from 148 to 2,797 yd. In comparing the mean daily distance covered by 2 groups of equal size it was found that one moved significantly further than the other. More trips were made to permanent water holes between 1300 and 1500 hr and during the dry season than at other times. The frequency of group progressions was greatest at 0700 to 1000 and 1600 to 1900 hr. Study of food habits shows that they were opportunistic omnivores. Elephants were the greatest food competitors of the vervets. The monkeys had at least 16 potential predators. Outside of parks and reserves the greatest predator was the European commercial trapper. Ecological characteristics of vervets and their niche separation from baboons are discussed.
We present new evidence supporting the hypothesis that a large raptor was responsible for the death of the c. 2.0-Myr-old Taung child, holotype of the early hominin species Australopithecus africanus. We compare the Taung child's skull with those of monkeys killed and eaten by modern crowned eagles, Stephanoaetus coronatus, in the Ivory Coast's Tai Forest. Close inspection of primate feeding remains from these large, powerful raptors reveals scratch marks in the orbital, frontal, temporal, parietal and occipital regions. Scratches similar in size and distribution are also present on the Taung child's skull. The new taphonomic evidence, combined with previously recognized similarities in breakage patterns and other assemblage characteristics, bolsters the case that a large bird of prey was responsible for the death of the juvenile hominin from Taung.
Spatial variation in predation risk generates a ‘landscape of fear’, with prey animals modifying their distribution and behaviour in response to this variable predation risk. In systems comprising multiple predators and prey species, a key challenge is distinguishing the independent effects of different predator guilds on prey responses. We exploited the acoustically distinct alarm calls of samango monkeys, Cercopithecus mitis erythrarchus, to create a predator-specific landscape of fear from eagles to assess its impact on space use within mixed regressive–spatial regressive models incorporating data on resource distribution and structural characteristics of the environment. The landscape of fear from eagles was the most significant determinant of samango range use, with no effect of resource availability. The monkeys also selected areas of their range with higher canopies and higher understory visibility, behaviour consistent with further minimizing risk of predation. These results contrast with those of vervet monkeys, Chlorocebus aethiops pygerythrus, at the same site for which the landscapes of fear from leopards and baboons were the most significant determinants of space use. While highlighting that predation risk is a key driver of primate behaviour in this population, the landscapes of fear experienced by samango monkeys and vervet monkeys appear to differ despite exposure to identical predator guilds. This emphasizes the importance of distinguishing between the risk effects of different predators in understanding prey ecology, but also that closely related prey species may respond to these predator-specific risks in different ways.
Models based on species distributions are widely used and serve important purposes in ecology, biogeography and conservation. Their continuous predictions of environmental suitability are commonly converted into a binary classification of predicted (or potential) presences and absences, whose accuracy is then evaluated through a number of measures that have been the subject of recent reviews. We propose four additional measures that analyse observation-prediction mismatch from a different angle – namely, from the perspective of the predicted rather than the observed area – and add to the existing toolset of model evaluation methods. We explain how these measures can complete the view provided by the existing measures, allowing further insights into distribution model predictions. We also describe how they can be particularly useful when using models to forecast the spread of diseases or of invasive species and to predict modifications in species’ distributions under climate and land-use change.
Cercopithecus aethiops in Amboseli National Park, Kenya, are preyed upon by mammalian carnivores, eagles, baboons, and snakes. High-ranking adult males and females gave alarm calls more often than low-ranking adult males and females. There was some tendency for females who alarm-called most often to precede other females in group progressions. Adult males who gave most alarm calls were more likely than other males to have fathered the group's juveniles and infants. Among adult females there was no correlation between number of offspring and frequency of first alarm calls. The offspring of high-ranking females may have been more vulnerable than other immatures to predation, possibly in part a consequence of the tendency of the offspring of high-ranking females to precede other juveniles in group progressions. Vervets of all age/sex classes alarm-called most at predators to which they themselves seemed to be most vulnerable. Adult vervets gave relatively few alarm calls to predators to which only their offspring were vulnerable, even though such alarm calls would have been of low cost to themselves and of great potential benefit to their offspring. Some aspects of the alarm-calling behaviour of vervet monkeys are consistent with the hypothesis that it has evolved to benefit kin: in other respects their alarms appear to have the consequence of benefiting only the alarmists themselves.-from Authors
1. A group of 32 yellow baboons (Papio cynocephalus) in the Masai-Amboseli National Park, Kenya, caught and ate 45 vertebrate prey items during 2519.19 hours of observation. 2. Eighty percent of the prey items were mammals and the most frequently eaten species were African hares (Lepus capensis), vervet monkeys (Cercopithecus aethiops) and neonate gazelle (Cazella granti and G. thomsoni) in that order. The details of predatory behavior for each prey species are described. 3. Rates of predation were significantly higher during the long dry season than during other months of the year, although no correlation was found between total monthly rainfall and monthly rates of predation. A lognormal model however provided a good fit to the monthly rate of predation data suggesting that the rate of predation by Amboseli baboons was affected by several factors that acted multiplicatively with respect to each other and were themselves related to rainfall or dryness. 4. A mean of 2.3 individuals fed directly from the carcass of each prey item. A mean of 3.5 individuals per prey item fed directly or indirectly, i.e., on scraps, from each carcass. In general, both the number of individuals who fed from each carcass and the duration of their feeding bouts was dependent upon the gross body size of the prey item. Adult males fed directly from the carcass of prey items for about three times more minutes than expected from their number in the group; other classes of individuals fed directly from prey carcasses for only one-fourth as many minutes as expected. In general, an adult male would be expected to feed on each category of vertebrate prey at least once per year, while individuals of all other age-sex classes would be expected to feed on most prey categories only once every two years. 5. The most frequent social behavior around prey items was agonistic bouts; no cooperation, simultaneous feeding or specific begging gestures were observed. 6. Estimates of the total number of prey killed annually by Amboseli baboons indicate that baboon predation probably has a negligible effect on prey populations other than vervet monkeys. 7. It is speculated that the need for vitamin B12 underlies baboon predatory behavior, and perhaps that of other primate species as well.
A technique for measuring the ‘risk of predation’, in an energy currency, is described. Experiments on free-living blue tits determined the extent to which feeding in a risky site was compensated by making food easier to obtain. The birds were trained to use operant feeding devices which were placed at different distances from the edge of woodland tree cover. The reward schedules at the feeders were controlled by a computer, which adjusted the number of hops required to obtain a food reward in relation to the extent to which each feeder was used. When the feeders were used equally the reward schedules stabilized and were recorded. There was little difference in the final reward schedules of feeders placed under the cover of trees, but the frequency of reinforcement required to persuade the birds to feed in the open rose dramatically at relatively short distances (1·5m) from cover.
Investigates patterns of predation in Papio populations across Africa. The primary predators of baboons are the terrestrial carnivores; in order of importance leopards Panthera pardus, lions Panthera leo and hyaena. In terms of prey selection, leopards are more likely to take 1) adults than juveniles and 2) males than females. While lion attacks are strictly diurnal, leopards will attack during both the day and night. However, both predators are usually limited to conducting attacks when and/or where visibility is limited. Leopards are about twice as successful as lions at hunting baboons. Nocturnal leopard hunts were more successful than diurnal hunts when twilight cases were excluded. Leopard attacks at sleeping sites were more likely to end in prey capture than attacks at waterholes. Male baboons are more likely to retaliate than females, and such behaviour effectively deters predators. Males are paticularly aggressive towards leopards, where in 4/11 cases the leopard was killed. -from Author
Discovery of the uses and later the invention of fire-making are fundamental to humanity. Following reports over the last decade of traces of fire found on Lower Pleistocene archaeological sites in eastern Africa, the dating of the control of fire by hominids has become a controversial issue. In this paper we critically review the contexts and, in the light of a battery of archaeometric techniques, the nature of reported instances of fire from Koobi Fora and Chesowanja in Kenya, and from Gadeb and the Middle Awash in Ethiopia. We conclude with a discussion of the roles fire may have played in the lifeways of early Pleistocene savanna-living hominids.
We examined the relationship between self-reported fear of large carnivores and the demographic characteristics of villagers living in a rural district adjacent to Serengeti National Park in Tanzania. Data were obtained from 593 respondents living in 8 villages. The intensity of verbally expressed attitudes was heavily dependent on whether the attitude object was of a general or a specific category. Level of self-reported fear was much higher for specific species of large carnivores than for broad verbal categories like concern over safety due to carnivores in general. Women were more afraid than men. The elderly expressed lower fear than other age groups, but only in response to the general category question. Level of fear was positively correlated with educational level. For almost all questions, villagers living further away from the national park expressed more fear than villagers living closer to the park. Fear can influence attitudes toward wildlife. Understanding whether encounters with wildlife are experienced as positive or negative can help in forming management strategies that are effective in reducing human–wildlife conflicts.