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Many studies have shown that behavioral responses to the risk posed by predators can carry costs for prey by reducing fecundity or survival, with consequent effects on population dynamics. Responses to risk include increased vigilance and reduced foraging, movement to safe habitats, increases or decreases in group size, and changes in patterns of movement. While we know that prey can detect and respond to both long term (LT) and short term (ST) variation in risk, field studies have only recently begun to consider how these responses might differ. Here, we hypothesize that prey movement patterns should respond differently to cues of LT and ST variation in risk. Specifically, cues of elevated LT risk might lead to decreased movement to improve the assessment of ST risk, while elevated ST risk might favor increased movement to reduce the proximity or duration of risks that are already assessed to be acute. We further hypothesize that decreases in movement are likely to be a general response to LT risk, while responses to ST risk are likely to vary in a manner that depends on the type of predator. In Liuwa Plain National Park, we found that wildebeest movements responded to the local intensity of predator use (LT risk), after controlling for other seasonal, diurnal and bottom-up effects. Speed decreased considerably and turning angles increased considerably, combining to markedly decrease linear movements. In contrast, immediate encounters with predators (ST risk) typically provoked fast, linear flight, and this effect was stronger for encounters with coursing predators. The effect of long term risk was to cause wildebeest to move more slowly and less linearly, i.e. to slow down and turn around, as part of a suite of behavioral responses, which also includes increased vigilance, that promote cautious assessment of ST risks when in locations with high levels of LT risk. This result has broad implications of understanding the influence of predation risk on foraging patterns of ungulates as this relationship is much more complex than simple avoidance of areas of ‘high risk’.

Conservation of competitively subordinate carnivores presents a difficult challenge because they are limited by dominant competitors. Prey depletion is one of the leading causes of large carnivore decline worldwide, but little is known about the net effect of prey depletion on subordinate carnivores when their dominant competitors are also reduced. African wild dogs are often limited by high densities of dominant competitors, particularly lions. We measured African wild dog density and survival, using mark-recapture models fit to 8 years of data from 425 known individuals in the Greater Kafue Ecosystem, Zambia. The GKE is affected by prey depletion, particularly of large herbivores, and thus the density of lions is significantly lower than ecologically comparable ecosystems. Counter to expectations from mesopredator release theory, wild dog density in GKE was far lower than comparable ecosystems with higher lion and prey density, though annual survival rates were comparable to large and stable populations. Average pack size was small and home range size was among the largest recorded. Our results show that low lion density did not competitively release the GKE wild dog population and we infer that the low density of wild dogs was a product of low prey density. Our results suggest that there is an optimal ratio of prey and competitors at which wild dogs achieve their highest densities. This finding has immediate implications for the conservation of the endangered African wild dog, and broad implications for the conservation of subordinate species affected by resource depletion and intraguild competition.

Despite some controversy, a wide range of research across multiple taxa have established that carnivores strongly influence prey population dynamics both through direct offtake and indirect risk effects. Because of these powerful top-down effects carnivores can influence ecosystems across multiple trophic levels. Here we discuss research addressing carnivore direct- and indirect effects on prey, and how these effects can influence overall ecosystem structure and function.

Interspecific competition between large carnivores is not well understood due to the complexity of carnivore guild dynamics and the array of ecological and human factors affecting them. The loss of a carnivore guild's dominant species can therefore provide considerable insights. We evaluated spotted hyaena density and demography from Zambia's Liuwa Plain National Park, a recovering ecosystem where the hyaena's main competitor, the African lion, was severely reduced to 3–5 animals. Using data from 233 individuals in five clans and mark-resight robust design models we estimated population size, density, age and sex-specific annual survival rates for the hyaena population from 2010 to 2013 and tested for the effect of human settlements, prey density, competition with lions and hyaena clan size on mean hyaena survival. We estimated a minimum density of 0.13 hyaenas/km2 and maximum density of 0.52 hyaenas/km2. Density fluctuated with seasonal migrations of the main prey species, the blue wildebeest. Mean annual survival across all age classes was 0.93 (95%CI: 0.79–0.99). With high survival rates across all sex and age classes, we found no detectable effects of ecological or anthropogenic factors on survival. These results suggest that the combination of abundant prey, weak human-carnivore conflict, and weak competition from lions provide very favourable conditions for hyaena survival. Additional investigations of hyaena demography concurrent with lion population recovery efforts can provide considerable insights into the dynamics of carnivore competition and predation in African savannahs and the human and ecological factors affecting them.

Large carnivores are in rapid global decline, with a broad array of consequences for the ecosystems they inhabit. To efficiently detect and address these declines requires unbiased and precise demographic data. Unfortunately, the characteristics that make large carnivores extinction-prone also pose serious challenges to obtaining these data. Rapid survey methods exist, but provide only relative measures of abundance, cannot detect declines before they become large, and provide little or no information about the causes of decline. African lions (Panthera leo) are declining throughout their range, making accurate monitoring of remaining populations urgent. We provide statistically rigorous estimates of population size, trends, survival rate and age–sex structure from Zambia’s South Luangwa lion population from 2008 to 2012, just prior to cessation of hunting in 2013. Mark-recapture models fit to data from intensive monitoring of 210 individual lions in 18 prides and 14 male coalitions indicated a declining population, low recruitment, low sub-adult and adult male survival, depletion of adult males, and a senescing adult female population. Trophy hunting was the leading cause of death, with 46 males harvested. Based on these data we recommend continuing the hunting ban at least to 2016 to allow recovery, with substantially reduced quotas, age-limits, and effective trophy monitoring mandated thereafter should hunting resume. Similar data from intensive monitoring of key Zambian lion populations is required to evaluate effects of the hunting ban and provide management guidance. Effectively integrating intensive long-term monitoring and rapid survey methods should be a priority for future management and monitoring of carnivore species.

Although carnivores are in global decline, diverse carnivore communities are common in sub-Saharan Africa, where more than 20 species may co-occur. Though intraguild competition and predation can limit the set of species that coexist, most carnivores have traits that decrease the impacts of interspecific competition on fitness, a pattern that promotes coexistence. An increasing human population and demand for natural resources (e.g. farming) has fragmented landscapes, reduced available prey, and elevated rates of conflict. These anthropogenic pressures tend to eliminate large carnivores first, which can have cascading effects on ecosystem function (e.g. mesopredator release). Anthropogenic pressures might also affect mesocarnivores directly, but this hypothesis has received little research attention to date. Here, we used camera surveys to describe spatial and temporal patterns of carnivore occupancy in a mixed-use landscape in Kenya. This landscape included a community conservation area and seasonally occupied human settlement and livestock grazing areas. We detected 21 carnivore species and examined occupancy patterns for the 12 most frequently detected. Differences among species in responses to environmental conditions supported a hypothesis of spatial niche partitioning. Differences in the temporal activity patterns of the apex predators and mesocarnivores supported a hypothesis of temporal niche partitioning. Human land use altered occupancy patterns in 10 of 12 species. Apex predator occupancies were lower in more anthropogenically disturbed areas, but mesocarnivore occupancies were not inversely related to apex predators, contrary to the mesopredator release hypothesis. Our results suggest that a diverse carnivore community persists in this mixed use landscape because of seasonal variation in human land use.

Apex carnivores around the world have experienced rapid population declines and local extirpation due to anthropogenic pressures, and they are increasingly restricted to government-protected areas (GPAs). Though GPAs are critical for carnivore conservation, mixed-use landscapes may be crucial for sustaining viable populations. Few studies, particularly in Africa, have examined joint use of a landscape by people and conflict-prone carnivores, such as the African lion ( Panthera leo ), in a situation where conflict is low. In southern Kenya, we studied a lion population in an unfenced rangeland occupied by the Maasai people and their livestock. The Maasai shift their settlements and grazing areas seasonally across a permanent river, a practice we hypothesized might promote coexistence. We radio-collared lions ( n = 6) to determine density and document spatial patterns in response to seasonal movements of people in a Conservation Area and buffer zone (250 km 2 ). Despite high livestock density, lion density was comparable to many GPAs (0.136 individuals/km 2 ). Lion spatial distribution and habitat selection shifted in relation to seasonal movements of people and livestock. Conflict was low, likely because lions increased their use of the Conservation Area and dense habitats when people were nearby. Lion responses to human movements reduced access to permanent water, but not prey. A land use system based on temporary settlements and grazing areas allowed lions to co-occur with people and livestock at high density. These results suggest a general strategy for the conservation of apex carnivores outside of GPAs, focusing on areas that exhibit spatiotemporal variation in human land use.

Considerable research has tested two axioms about antipredator behaviour: prey may respond to temporal variation in risk (the risky times hypothesis) or to spatial variation in risk (the risky places hypothesis). The risk allocation hypothesis extends the risky times hypothesis, noting that the context into which a period of risk or safety is imbedded should affect the level of response, and predicting that vigilance should be greatest during a brief pulse of risk and lowest during a brief pulse of safety. We tested these models using natural variation in true predation risk, by observing elk, Cervus elaphus, in the presence or absence of wolves, Canis lupus, on three sites in the Greater Yellowstone Ecosystem, over 4 winters. Elk were exposed to wolves frequently in the Northern Range, intermittently in the Gallatin Canyon, and never in the Elkhorn Mountains. We used GLM to control the effects of herd size and composition while testing for responses of vigilance to daily wolf presence (temporal variation) and to site-specific, background levels of risk (spatial variation). The data gave strong support to the risk allocation hypothesis and equivocal support to the risky times hypothesis, and did not support the risky places hypothesis. Contrary to the risky places hypothesis but as predicted by risk allocation, Gallatin elk were more vigilant than Northern Range elk despite lower background risk in the Gallatin Canyon. The contradictory predictions of the risk allocation and risky places hypotheses have important ramifications for research on the ecological consequences of antipredator behaviour.

Risk effects arise when prey alter their behavior in response to predators, and these responses carry costs. Empirical studies have found that risk effects can be large. Nonetheless, studies of predation in vertebrate conservation and management usually consider only direct predation. Given the ubiquity and strength of behavioral responses to predators by vertebrate prey, it is not safe to assume that risk effects on dynamics can be ignored. Risk effects can be larger than direct effects. Risk effects can exist even when the direct rate of predation is zero. Risk effects and direct effects do not necessarily change in parallel. When risk effects reduce reproduction rather than survival, they are easily mistaken for limitation by food supply.

We investigated spatial organization and patterns of interaction in a population of the little-known striped hyaena, Hyaena hyaena. We use the resulting data to test hypotheses of group formation that predict that female striped hyaenas will be solitary in response to overdispersion of food resources and males will be solitary in response to overdispersion of females. Based primarily on anecdotal or historical information, striped hyaenas have been described as solitary. We show that, as predicted, striped hyaenas of both sexes are behaviourally solitary. However, they form stable, polyandrous spatial groups composed of multiple males and a single female. We suggest that male coalition formation may be the result of male strategies to optimize trade-offs between the number of female ranges defended and the effectiveness of that defence when females are solitary and maintain large territories. Nevertheless, the joint male defence of a territory (of any size) containing only a single female would not be predicted by any major hypothesis for the evolution of group living, in this or any other species.

The highly masculinized genitalia of female spotted hyenas Crocuta crocuta is unique among mammals: Crocuta have no external vagina so urination, penile intromission and parturition take place through the clitoris, which mimics a fully erectile male penis. Among hyenids, virilization of external female genitalia has previously been observed only in Crocuta, so functional explanations of masculinization have focused on aspects of social ecology unique to the species. Here we first show that the striped hyena Hyaena hyaena exhibits both unusual similarity in male and female androgen concentrations and transient genital anomalies characterized by a convergence in genital appearance among young males and females. We then evaluate hypotheses regarding the evolution of genital masculinization in the Hyaenidae and other taxa. Hyaena are behaviorally solitary, so discovery of unusual genital development patterns in this species does not support any current evolutionary models for masculinization in Crocuta, which all rely on the trait originating within a highly social species. Some hypotheses can be modified so that masculinization in Crocuta represents an extreme elaboration of a preexisting trait, shared as a homology with Hyaena.

We studied individual and herd level behavioural responses of elk to spatial and temporal variation in the risk of predation by wolves over three winters in the Upper Gallatin drainage, Montana, U.S.A. Within a given drainage, elk of both sexes moved into or closer to protective cover (timber) in response to wolf presence. Cow elk responded to elevated risk by increasing vigilance in exchange for foraging, and large mixed (cow, calf, spike) herds substantially decreased in size. In contrast, when wolves were present, bulls did not increase vigilance levels, or decrease feeding, and small bull-only groups slightly increased in size. As a consequence, small bull-only herds and large mixed-sex herds converged on a similar size when wolves were present. We think this response is a balancing of the benefits of risk dilution with increased detectability or attractiveness of larger herds to wolves. Based on proportions in the population, wolves overselected bulls and underselected cows as prey. Thus, bulls showed weaker antipredator responses than cows, despite facing a greater risk of predation. Using marrow fat content from elk killed by wolves as an indicator of body condition, bulls were in significantly worse body condition than cows throughout the winter, and condition deteriorated for both sexes as winter progressed. Overall, we conclude that antipredator behaviours carry substantial foraging costs, that bulls, because of their poorer body condition, are less able to pay these costs than cows, and that differences in ability to pay foraging costs probably explain sex-specific differences in antipredator behaviours.

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.

Adrenal glucocorticoid (GC) secretion is an important component of the response to stress in vertebrates. A short-term increase in circulating GCs serves to redirect energy from processes that can be briefly curtailed without harm, allowing energy to be directed towards eliminating or avoiding the stressor. In contrast, prolonged elevation of GCs can cause a broad range of pathologies, including reproductive suppression. We examined whether social subordination in wolves leads to chronically elevated GC levels, and whether this ‘social stress’ causes reproductive suppression of subordinates in cooperatively breeding species. Behavioural and endocrine data collected over 2 years from three packs of free-living wolves in Yellowstone National Park did not support this hypothesis. GC levels were significantly higher in dominant wolves than in subordinates, for both sexes, in all packs, in both years of study. Unlike other cooperatively breeding carnivores (e.g. dwarf mongooses, Helogale parvula, and African wild dogs, Lycaon pictus), high GCs in dominant wolves were not associated with high rates of aggression or agonistic interaction. Aggression increased for wolves of all ranks during mating periods, accompanied by a significant rise in GC levels. If chronic elevation of GCs carries fitness costs, then social stress in wolves (and many other social species) is a cost of dominance, not a consequence of subordination. The specific behavioural correlates of dominance that affect GC levels appear to vary among species, even those with similar social systems.

In most cooperatively breeding birds and mammals, reproductive rates are lower for social subordinates than for dominants, and it is common for reproduction in subordinates to be completely suppressed. Early research conducted in captivity showed that losing fights can increase glucocorticoid (GC) secretion, a general response to stress. Because GCs can suppress reproduction, it has been widely argued that chronic stress might underlie reproductive suppression of social subordinates in cooperative breeders. Contradicting this hypothesis, recent studies of cooperative breeders in the wild show that dominant individuals have elevated GCs more often than do subordinates. The findings that elevated GCs can be a consequence of subordination or a cost of dominance complicate the conventional view of social stress, with broad ramifications for the evolution of dominance and reproductive suppression.

Because the sex of mammals is chromosomally determined, populations generally produce a similar proportion of males and females. However, it has been recognized for more than century that individuals might increase their fitness by over-producing offspring of one sex, under certain conditions. Small biases in the secondary sex ratio are seen in many vertebrates. Here, we report that the sex ratio of primiparous African wild dogs (Lycaon pictus) is strongly biased in favor of sons (63%), while multiparous females produce an excess of daughters (64%). The direction of these biases is predicted by individual females' need for subordinate helpers. For humans, elevated estrogens have been hypothesized to bias the secondary sex ratio toward males. Consistent with this hypothesis, primiparous female wild dogs had basal estrogen levels double those of multiparous females.

An individual’s inclusive fitness is derived by augmenting its traditional Darwinian fitness by certain components, and stripping it of others (Hamilton 1964). The component to be added is the sum of all eVects of the individual on his neighbours, weighted by the coeYcient of genetic relationship (r) between them. In the original derivation of inclusive fitness, the component to be subtracted was verbally defined as ‘all components which can be considered as due to the individual’s social environment’ (Hamilton 1964). It is not widely appreciated that this verbal definition of the component to be subtracted does not agree with its algebraic definition. Creel (1990a) used Hamilton’s algebraic definition of inclusive fitness to show that the component to be subtracted, e 0 , is actually equal to the average eVect

African wild dogs are 20–25 kg social carnivores whose major prey are ungulates ranging from 15 to 200 kg. In the Selous Game Reserve, Tanzania, wild dog pack size ranged from three to 20 adults (3–44 including yearlings and pups). Data from 905 hunts and 404 kills showed that hunting success, prey mass and the probability of multiple kills increased with number of adults. Chase distance decreased with number of adults. None the less, the distribution of per capita food intake across adult pack size was U-shaped, with a minimum close to the modal pack size. A similar result has been used to conclude that cooperative hunting does not favour sociality in lions (Packer et al. 1990, Am. Nat., 136, 1–19), and to argue that cooperative hunting is not responsible for group living in any carnivore (Caro 1994, Cheetahs of the Serengeti Plains: Group Living in an Asocial Species). Daily per capita food intake only accounts for variation in the benefits to cooperative hunting, ignoring variation in costs. For Selous wild dogs, per capita food intake per km chased peaked close to the modal adult pack size (where per capita food intake per day was near its minimum). Thus, the energetics of cooperative hunting favour sociality in Selous wild dogs. Analyses that incorporate variation in both costs and benefits of hunting may show that cooperative hunting favours sociality in other species where its influence has previously been rejected.

Abstract. Slender mongooses, Herpestes sanguineus , are solitary but males sometimes form loose, non-aggressive associations. Since 1975, sightings of marked animals in the Serengeti National Park, Tanzania, indicate that (1) up to four males may jointly use the same home range, each of which may overlap the ranges of up to six females but no other males; (2) association membership can be stable for up to 7 years; (3) members of an association generally appear on the study site together as young adults, presumably having immigrated from off the study site; and (4) larger associations have persisted for longer periods. DNA fingerprinting confirms that paternity is not monopolized by any single association member, and that association members can be closely related. These results suggest that associations of male slender mongooses are coalitions that exclude other males from access to females within a common territory. Coalitions have also been reported within other mongoose species; this form of escalated mate competition, which has been generally associated only with certain primates and felids, may be more widely distributed.

Abstract. Dwarf mongooses, Helogale parvula, are group-living carnivores in which the oldest male and female dominate reproduction, while subordinates tolerate reproductive suppression and provide care for the offspring of the oldest pair. Subordinates of both sexes, however, mate and subordinate females occasionally become pregnant. In addition, a model of 'power-sharing' in social groups (Vehrencamp 1983, Anim. Behav., 31, 667-682) predicts that dominant individuals should cede some fitness to subordinates, particularly older, higher-ranking individuals not closely related to the dominants, in order to retain them within the group. Human multilocus probes (Jeffreys' 33.15 and 33.6) were used to 'fingerprint' dwarf mongooses from nine different packs in the Serengeti National Park, Tanzania. The results demonstrate that subordinates of both sexes obtain direct fitness: 24% of young had subordinate fathers, while 15% had subordinate mothers. Multiple paternity can occur within a single female's litter. Those subordinates that reproduced were of high social rank and tended to be distantly related to the same-sex dominant, as predicted by Vehrencamp's model. The number of yearlings produced by subordinate females was similar to that predicted by the model. Subordinate males father a relatively high proportion of offspring given their frequency of mating, while subordinate females mate relatively more often than they produce offspring, consistent with previously inferred differences between the mechanisms of male and female reproductive suppression (Creel et al. 1992, Anim. Behav., 43, 231-245). Even though DNA analyses indicate that subordinates produced a substantial proportion of young born in this population, the magnitude of direct fitness obtained by subordinates was still low compared with the magnitude of indirect fitness obtained by helping.

Behavioural, demographic and endocrine data were collected from a wild population of dwarf mongooses, Helogale parvula, in Serengeti National Park, Tanzania. The data show that subordinate females are reproductively suppressed by a complex of endocrine and behavioural mechanisms, while subordinate males are reproductively suppressed primarily by behavioural mechanisms. Subordinate females have (1) low baseline oestrogen levels, (2) low mating rates, and (3) low peak oestrogen levels during mating periods. Subordinate males (1) have low mating rates, and (2) are the recipients of increased aggression during mating periods, but (3) have androgen levels indistinguishable from those of dominants, both during and away from mating periods. Mechanistic differences between the sexes suggest that the selection pressures favouring reproductive suppression may also differ between the sexes.

Indirect fitness is the portion of an individual's inclusive fitness due to the effects of the individual's behaviour on the reproductive value of non-descendant kin. Indirect fitness may play a role in the evolutionary maintenance of cooperative breeding, in which some individuals help others to breed. Recently, theoretical and empirical studies have addressed the future component of indirect fitness, i.e. the effects of an individual's current behaviour on the subsequent survival and reproduction of nondescendant kin. A difficulty in accounting future fitness effects arises when generations overlap in a cooperative breeding system (as is normally the case). Individuals of one generation can serve as helpers to individuals of the previous generation, ‘returning from the future’ to compound their ancestors' fitness. This paper classifies the types of fitness effects arising from generational interactions in cooperative breeding systems. This classification is then used to suggest methods of measuring future indirect and future direct (individual) fitness so that they are directly comparable.