Inadequacy of activity time as a niche difference: the case of diurnal and nocturnal raptors

Summary It has been assumed that differences in activity time of diurnal (Falconiform) and nocturnal (Strigiform) raptors reduce competition for food by giving them access to different prey resources. Consequently, dietary similarity should be greater between synchronously active raptors (either diurnal or nocturnal) than between asynchronous ones (diurnal versus nocturnal). Using five collective raptor assemblages I tested the hypothesis that the statistical distribution of food overlaps between synchronous raptors (Falconiform x Falconiform and Strigiform x Strigiform combined) should be composed of larger figures than that obtained from asynchronous pairs (Falconiform x Strigiform). Both a conservative (Kolmogorov-Smirnov test with Chisquare approximation) and a powerful (Mann-Whitney U-test) nonparametric procedure were used to deal with the problem of the degrees of freedom to be assigned to non-indepedent observations such as overlaps. The tests consistently failed to reject the null hypothesis, thus pointing to the inadequacy of temporal segregation as a means to partition prey resources between diurnal and nocturnal raptors. I propose that this can be accounted for by two factors, acting singly or in combination: a) that both Falconiforms and Strigiforms extend their hunting activities to crepuscular hours thus sharing prey of that activity period; b) that reputedly diurnal and nocturnal prey become vulnerable to predators of asynchronous hunting time by extending their activities in the field. Based on records of interspecific territoriality, prevation, and interference competition I propose that the evolution of nocturnality in Strigiforms might be more clearly related to interference interactions rather than exploitation competition with Falconiforms.     

Food partitioning between breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in southern Brazil.

I examined the diet of breeding White-tailed Kites (Elanus leucurus; Aves; Accipitridae) and Barn Owls (Tyto alba; Aves; Tytonidae) in an agrarian area of southern Brazil by analyzing regurgitated prey remains. The objective was to evaluate how these raptors, which differ markedly in their hunting activity periods (owls are nocturnal and kites diurnal), share their mammalian food component. 2,087 prey consumed by Barn Owls and 1,276 by White-tailed Kites were identified. They presented a high overlap of food-niches (Piankas index was 0.98). Based on the daily activity period of their main small mammal prey, a lower overlap would be expected. The crepuscular/nocturnal Mus musculus was the main prey for the diet of breeding Barn Owls (81%) and White-tailed Kites (63%). This small exotic rodent provided 63% of the small mammal biomass ingested by owls and 44% by kites. Larger native small mammals were also considered important for the diet of kites, mainly because of their biomass contribution. Although these raptors differ markedly in their hunting activity periods, Barn Owls and White-tailed Kites are very similar predators in southern Brazil, overlapping their diets.     

Prey availability affects territory size,but not territorial display behavior,in green anole lizards

The availability of food resources can affect the size and shape of territories, as well as the behaviors used to defend territories, in a variety of animal taxa. However, individuals within a population may respond differently to variation in food availability if the benefits of territoriality vary among those individuals. For example, benefits to territoriality may differ for animals of differing sizes, because larger individuals may require greater territory size to acquire required resources, or territorial behavior may differ between the sexes if males and females defend different resources in their territories. In this study, we tested whether arthropod abundance and biomass were associated with natural variation in territory size and defense in insectivorous green anole lizards, Anolis carolinensis. Our results showed that both male and female lizards had smaller territories in a habitat with greater prey biomass than lizards in habitats with less available prey, but the rates of aggressive behaviors used to defend territories did not differ among these habitats. Further, we did not find a relationship between body size and territory size, and the sexes did not differ in their relationships between food availability and territory size or behavioral defense. Together, these results suggest that differences in food availability influenced male and female territorial strategies similarly, and that territory size may be more strongly associated with variation in food resources than social display behavior. Thus, anole investment in the behavioral defense of a territory may not vary with territory quality.     

Behavioral responses of male elk to hunting risk

Prey respond to predation risk with a range of behavioral tactics that can vary based on space use and hunting mode of the predator. Unlike other predators, human hunters are often more spatially and temporally restricted, which creates a period of short-duration, high-intensity predation risk for prey. Consequently, identifying the roles different hunting modes (i.e., archery and rifle), hunts for targeted and non-targeted species, and landscape features play in altering spatial and temporal responses of prey to predation risk by humans is important for effective management of harvested populations. From 2009 to 2016, we used a large-scale experiment including 50 animal-years of location data from 38 unique male elk (Cervus canadensis) to quantify changes in movement and resource selection in response to hunters during 3 separate 5-day controlled hunts for antlered males (elk archery, deer [Odocoileus spp.] rifle, and elk rifle) at the Starkey Experimental Forest and Range in northeast Oregon, USA. We evaluated competing hypotheses regarding elk responses to varying levels of prey risk posed by the different hunt types. We predicted that the strength of elk behavioral responses would increase with perceived hunter lethality (i.e., weak response to elk archery but similar response to elk and deer rifle hunts) and that prey response would be closely associated with hunter activity within the diel cycle (greater during diurnal than nocturnal hours) and across hunting seasons. Elk responses were strongest during diurnal hours when hunters were active on the landscape and were generally more pronounced during both rifle hunts than during the archery hunt (supporting our perceived lethality hypothesis). Male elk avoided open roads across all periods except during nocturnal hours of the breeding season and alternated between avoidance of areas with high canopy cover during nocturnal hours and selection during diurnal hours. In combination these patterns led to distinct distributional changes of male elk from pre-hunt to hunt periods. Patterns of male elk selection highlight the importance of managing for heterogeneous landscapes to meet a variety of habitat, harvest, hunter satisfaction, and escapement objectives.     

Cooperative hunting roles among taï chimpanzees

All known chimpanzee populations have been observed to hunt small mammals for meat. Detailed observations have shown, however, that hunting strategies differ considerably between populations, with some merely collecting prey that happens to pass by while others hunt in coordinated groups to chase fast-moving prey. Of all known populations, Taï chimpanzees exhibit the highest level of cooperation when hunting. Some of the group hunting roles require elaborate coordination with other hunters as well as precise anticipation of the movements of the prey. The meat-sharing rules observed in this community guarantee the largest share of the meat to hunters who perform the most important roles leading to a capture. The learning time of such hunting roles is sometimes especially long. Taï chimpanzee males begin hunting monkeys at about age 10. The hunters’ progress in learning the more sophisticated hunting roles is clearly correlated with age; only after 20 years of practice are they able to perform them reliably. This lengthy learning period has also been shown in some hunter-gatherer societies and confirms the special challenge that hunting represents.     

Wolf predation on moose and roe deer: chase distances and outcome of encounters

We examined chase distances of gray wolves Canis lupus Linnaeus, 1758 hunting moose Alces alces and roe deer Capreolus capreolus, and recorded details of encounters between wolves and prey on the Scandinavian Peninsula, 1997–2003. In total, 252 wolf attacks on moose and 64 attacks on roe deer were registered during 4200 km of snow tracking in 28 wolf territories. Average chase distances were 76 m for moose and 237 m for roe deer, a difference likely due to variation in body size and vigilance between prey species. A model including prey species, outcome of the attack, and snow depth explained 15–19% of the variation found in chase distances, with shorter chase distances associated with greater snow depth and with successful attacks on moose but not on roe deer. Wolf hunting success did not differ between prey species (moose 43%, roe deer 47%) but in 11% of the wolf attacks on moose at least one moose was injured but not killed, whereas no injured roe deer survived. Compared with most North American wolf studies chase distances were shorter, hunting success was greater, and fewer moose made a stand when attacked by wolves in our study. Differences in wolf encounters with moose and roe deer likely result from different anti-predator behaviour and predator-prey history between prey species.     

The guild structure of a community of predatory vertebrates in central Chile

Summary The trophic ecology of eleven predator species (Falconiforms: Buteo polyosoma, Elanus leucurus, Falco sparverius, Geranoaetus melanoleucus, Parabuteo unicinctus; Strigiforms: Athene cunicularia, Bubo virginianus, Tyto alba; Carnivores: Dusicyon culpaeus; Snakes: Philodryas chamissonis, Tachymenis peruviana) in two nearby localities of central Chile is analyzed. The localities exhibit the typical climate (hot-dry summers, coldrainy winters), and vegetation (chaparral), of mediterranean ecosystems. Densities of the staple prey (small mammals) were estimated by seasonal trapping during two years in both open and dense patches of chaparral.The trophic parameters examined are: 1) proportion of diurnal, crepuscular, or nocturnal prey found in the predators' diet; 2) relationship between abundance of different mammalian prey in the predators' diet, and in both open and densely vegetated habitat patches; 3) mean weight and variance of weight of small mammal prey consumed; 4) average weight of the predators; 5) food-niche breadth of the predators; 6) relationship between average weight of predators and mean weight of mammalian prey taken, its variance, and food-niche breadth; 7) overlap in food-niche between all the predator species; 8) guild packing of the predators. Parameters 1) and 2) are used to assess the importance of temporal and habitat segregation of the predators, respectively; parameters 3), 4), 5), and 6) provide information on the possibilities of partitioning the prey resources among the predators; parameters 1), 2), 7) and 8) are used to investigate the organization of the community in terms of guilds.Three niche dimensions seem to be important in determining the structure of the predator community: 1) hunting activity period (diurno-crepuscular, nocturno-crepuscular), 2) hunting habitat (open, or both open and dense patches), and 3) mean prey size taken. Segregation along these three axes results in generally low food niche overlaps (<54% in 47 of the 55 pairwise comparisons) among the predators, but it is not possible to determine whether this was produced by competitive interactions or stochastic differences. Three guilds (niche overlap >90% in pair-wise comparisons) can be recognized: a) the carnivorous-insectivorous guild formed by the diurnal raptors A. cunicularia and F. sparverius, which tend to hunt in open habitat patches; b) the herpetophagous guild formed by the diurnal snakes P. chamissonis and T. peruviana, which presumably hunt in open habitat patches; c) the carnivorous guild (highly specialized in the capture of two rodent species) formed by the diurnal raptors B. polyosoma, G. melanoleucus, P. unicinctus, and the carnivore D. culpaeus, which hunt in open habitat patches. The diurnal raptor E. leucurus is not clearly associated with any guild, and the only two nocturnal raptors in the community (B. virginianus and T. alba) exhibit marked differences in their trophic ecology.     

Movement,activity and hunting behaviour of leopards in the Cederberg mountains,South Africa

Few data are available on the behaviour of leopards in the absence of competing large predators and human impact, both of which are believed to influence leopard activity and movements. Remote camera traps and global positioning system (GPS) collars were used to quantify leopard activity in the Cederberg Mountains, seasonal and sexual differences in their movements, and determine whether nocturnal hunting success was related to lunar activity. Seventy‐seven per cent of camera‐trap photographs were at night, with a strong male bias (69%) in captures. Daily displacement using one location per day suggested that males moved significantly further than females. However, multiple locations (≥6 per day) showed no difference because males moved in a more linear fashion, but not further each day, than females. In the Cederberg Mountains, an open rocky habitat with low human impact and no competing predators, leopards were predominantly nocturnal, mainly hunting diurnal prey species. Hunting success was low: leopards travelled long distances between kills, with nocturnal hunting success higher on darker nights.     

Defence, intrusion and the evolutionary stability of territoriality

Territorial behaviour can only be adaptive if its costs are outweighed by its benefits. Territorial individuals incur costs by defending their territories against intruders. Usually these intruders are assumed to be non-territorial floaters attempting to take over the whole territory or neighbours trying to extend the borders of their own territory. We instead investigate how costs and benefits of territorial behaviour are affected by neighbours which invade to steal resources on a territory.We show analytically that in the absence of defence intrusion into neighbouring territories always pays and that even if territories are defended intrusion levels can still be high. Using a more detailed simulation model we find that territory defence usually disappears from the population even if owners have a strong advantage over intruders in terms of fighting costs or foraging efficiency. Defence and thus territoriality can only be evolutionarily stable if fighting costs for the intruder relative to the productivity of the territory are very high or if crossing the borders between territories carries additional costs.Our results show that stealing of resources by neighbours can have a considerable effect on the evolutionary stability of territory defence and thus territoriality itself. A more mechanistic model of territorial behaviour is needed to incorporate these kinds of mechanisms into a general theory on the evolution of territoriality.     

How does hunting influence activity and spatial usage in wild boar <Emphasis Type="Italic">Sus scrofa</Emphasis> L.?

Increasing wild boar (Sus scrofa L.) population densities all over Europe cause severe economic problems. In popular belief, the wild boar is a more or less diurnal species, causing only minor problems when undisturbed, but is assumed to become nocturnal and wide-ranging when opposed to hunting pressure. In our study, we investigated the impact of hunting and several environmental factors on movements, spatial utilisation and activity patterns by radiotelemetry. Activity pattern revealed a mean proportion of diurnal activity of 12% of all localisations with a monthly change. The wild boar showed increased diurnal activity on undisturbed feeding habitats, especially in early summer. Different hunting methods did influence activity and spatial utilisation in terms of activity and smaller home ranges in areas with only single hunt, although this might be biased by seasonal effects. Flight distances increased significantly after single hunt and capture incidents, but still ranged inside the annual home ranges. Battues did not influence the spatial utilisation before and after hunt significantly. In only 14% of the observed cases did wild boar show small scaled escape movements after battues. The overlaps of home ranges did not change after battues.     

Hunting behaviour in West African forest leopards

The leopard (Panthera pardus) is a major predator of mammals within the rainforest ecosystem of West Africa. Most of the available information on leopard hunting behaviour comes from studies conducted in open savannah habitats, while little is known about forest leopards. Our radio‐tracking data and scat analysis show that forest leopards differ in various ways from the savannah populations. Forest leopards are diurnal and crepuscular hunters who follow the activity pattern of their prey species. They exhibit seasonal differences in activity patterns, and they develop highly individualized prey preferences. These findings challenge the widespread notion of leopards as opportunistic nocturnal predators.     

You can’t run but you can hide: refuge use in frog tadpoles elicits density-dependent predation by dragonfly larvae

The potential role of prey refuges in stabilizing predator–prey interactions is of longstanding interest to ecologists, but mechanisms underlying a sigmoidal predator functional response remain to be fully elucidated. Authors have disagreed on whether the stabilizing effect of prey refuges is driven by prey- versus predator-centric mechanisms, but to date few studies have married predator and prey behavioural observations to distinguish between these possibilities. We used a dragonfly nymph–tadpole system to study the effect of a structural refuge (leaf litter) on the predator’s functional response, and paired this with behavioural observations of both predator and prey. Our study confirmed that hyperbolic (type II) functional responses were characteristic of foraging predators when structural cover was low or absent, whereas the functional response was sigmoidal (type III) when prey were provided with sufficient refuge. Prey activity and refuge use were density independent across cover treatments, thereby eliminating a prey-centric mechanism as being the genesis for density-dependent predation. In contrast, the predator’s pursuit length, capture success, and handling time were altered by the amount of structure implying that observed shifts in density-dependent predation likely were related to predator hunting efficiency. Our study advances current theory by revealing that despite fixed-proportion refuge use by prey, presence of a prey refuge can induce density-dependent predation through its effect on predator hunting strategy. Ultimately, responses of predator foraging decisions in response to changes in prey availability and search efficiency may be more important in producing density-dependent predation than the form of prey refuge use.     

Food-niche differentiation in sympatric Hen Circus cyaneus and Montagu's Harriers Circus pygargus

Hen Harriers Circus cyaneus and Montagu's Harriers Circus pygargus are medium-sized raptors that differ in size (Hen Harrier being slightly bigger than Montagu's Harrier) and breeding system (Montagu's Harriers are semi-colonial and Hen Harriers defend nesting–hunting territories). In contrast, the diets of the two species when in sympatry are very similar. We evaluated food-niche differentiation among these coexisting raptor species and how between-species differences in body size and social system influence interspecific relationships. We present data from a study conducted in 1997 and 1998 in northeastern Madrid province (central Spain). Diet of the two species largely overlapped (55–95%) during the breeding season, but Hen Harriers preyed more often on larger species. This segregation was observed both in the average size of the primary prey (lagomorphs) and in the alternative prey (birds for Hen Harriers vs. insects for Montagu's Harriers), and was particularly apparent late in the season. Accordingly, feeding frequency of Montagu's Harriers, but not of Hen Harriers, increased later in the season. Size differences between species in prey brought to the nest were apparent for both males and females. Foraging behaviour also differed, as Hen Harriers spent more time hunting close to the nest than did Montagu's Harriers. This implies that segregation in foraging areas may also exist. Observed niche partitioning may relax the potential for competition between these species.     

Evolutionary Implications of Persistence Hunting: An Examination of Energy Return on Investment for !Kung Hunting

Hominins are smaller, slower, and weaker than most large mammals, yet they have been eating meat from freshly killed large mammals since before the invention of sophisticated weaponry. It is thought that they could have achieved this seemingly impossible feat through persistence hunting, a practice powered by endurance running. Essentially, one or more hunters pursue a prey animal in the heat of the day until it reaches the point of hyperthermia. This allows a hunter to safely kill the weakened animal at close range using methods such as beating, strangling, or spearing. The energy balance of this approach to getting food is controversial and has not been calculated previously. We examined the energy costs and gains of persistence hunting through several energy returned on investment (EROI) calculations based on synthesizing available field and laboratory data on the energy used by the hunters and the energy returned from the greater kudu (Tragelaphus strepsiceros). We estimate that the EROI of these hunter-gatherers hunting a kudu ranged from 26:1 to 69:1. The net energy gained from such an effort would sustain an average sized !Kung family for 6.7 to 11.2 days. The “profit” energy within these ranges would have supported the early human societies that practiced persistence hunting, contributing to the often-noted “leisure” characterizing many foraging societies (Sahlins 1974).     

Assessing differential prey selection patterns between two sympatric large carnivores

Several conceptual models describing patterns of prey selection by predators have been proposed, but such models rarely have been tested empirically, particularly with terrestrial carnivores. We examined patterns of prey selection by sympatric wolves ( Canis lupus ) and cougars ( Puma concolor ) to determine i) if both predators selected disadvantaged prey disproportionately from the prey population, and ii) if the specific nature and intensity of prey selection differed according to disparity in hunting behavior between predator species. We documented prey characteristics and kill site attributes of predator kills during winters 1999–2001 in Idaho, and located 120 wolf-killed and 98 cougar-killed ungulates on our study site. Elk ( Cervus elephus ) were the primary prey for both predators, followed by mule deer ( Odocoileus hemionus ). Both predators preyed disproportionately on elk calves and old individuals; among mule deer, wolves appeared to select for fawns, whereas cougars killed primarily adults. Nutritional status of prey, as determined by percent femur marrow fat, was consistently poorer in wolf-killed prey. We found that wolf kills occurred in habitat that was more reflective of the entire study area than cougar kills, suggesting that the coursing hunting behavior of wolves likely operated on a larger spatial scale than did the ambush hunting strategy of cougars. We concluded that the disparity in prey selection and hunting habitat between predators probably was a function of predator-specific hunting behavior and capture success, where the longer prey chases and lower capture success of wolf packs mandated a stronger selection for disadvantaged prey. For cougars, prey selection seemed to be limited primarily by prey size, which could be a function of the solitary hunting behavior of this species and the risks associated with capturing prime-aged prey.     

Heat stress in a high-latitude seabird: effects of temperature and food supply on bathing and nest attendance of great skuas Catharacta skua

Birds such as great skuas Catharacta skua adapted for successful breeding at high latitudes may experience problems of heat dissipation in mild climates. Great skuas spend time bathing at freshwater sites close to breeding territories and here, we examine impacts of heat stress on bathing, foraging and nest attendance of adults during three breeding seasons with marked variation in the availability of prey (1-group sandeels Ammodytes marinus ). Adults exhibited diurnal variation in bathing activity that matched heat-stress conditions. Moreover more birds bathed on days of higher average heat stress, suggesting that bathing plays a role in thermoregulation. Bathing numbers were lower in years of poor food availability, when adult attendance at territories was low, probably because lower attendance reduced the opportunity for parents to bathe without leaving chicks unattended. Chicks are normally guarded by female parents and fed by males but under conditions of low food availability territorial attendance of breeding pairs was particularly low on days of high heat stress, with chicks regularly left unattended at air temperatures exceeding 14°C. Unattended chicks are at risk of being killed by neighbouring conspecifics and survival of chicks to fledging was low in the two years of low sandeel stocks. Our study indicates that for great skuas, indirect effects of climate change on prey stocks and direct effects on heat stress experienced by adults may be additive.     

Aboriginal Burning Regimes and Hunting Strategies in Australia’s Western Desert

A large complement of Australia’s biotic web is dependent on a regular regime of burning, much of which is the result of firing by humans. Many researchers have suggested that moderate and repeated burning by Aborigines is a tool designed to enhance hunting efficiency. We present the first test of this with data on contemporary Martu Aboriginal burning and hunting strategies in the arid spinifex savanna of the Western Desert during the cool-dry season (May–August). Our results show a strong positive effect of mosaic burning on the efficiency of hunting burrowed prey (primarily conducted by women), but not larger mobile prey (primarily conducted by men). We suggest that regular anthropogenic disturbance through burning in Australia’s Western Desert may be important for sustaining biodiversity and habitat mosaics, but these effects may be maintained primarily by women’s hunting of burrowed game. We discuss the implications of these results for understanding variability in hunting strategies, issues of conservation, and land management policy for the region.     

Wait Until Dark? Daily Activity Patterns and Nest Predation by Snakes

Predation involves costs and benefits, so predators should employ tactics that reduce their risk of injury or death and that increase their success at capturing prey. One potential way that predators could decrease risk and increase benefits is by attacking prey at night when risks may be reduced and prey more vulnerable. Because some snakes are facultatively nocturnal and prey on bird nests during the day and night, they are ideal for assessing the costs and benefits of diurnal vs. nocturnal predation. We used automated radiotelemetry and cameras to investigate predation on nesting birds by two species of snakes, one diurnal and the other facultatively nocturnal. We predicted that snakes preying on nests at night should experience less parental nest defence and capture more adults and nestlings. Rat snakes (Pantherophis obsoletus) were relatively inactive at night (23–36% activity) but nearly always preyed on nests after dark (80% of nest predations). Conversely, racers (Coluber constrictor) were exclusively diurnal and preyed on nests during the times of day they were most active. These results are consistent with rat snakes strategically using their capacity for facultative nocturnal activity to prey on nests at night. The likely benefit is reduced nest defence because birds defended their nests less vigourously at night. Consistent with nocturnal predation being safer, rat snake predation events lasted three times longer at night than during the day (26 vs. 8 min). Nocturnal nest predation did not make nests more profitable by increasing the likelihood of capturing adults or removing premature fledging of nestlings. The disconnect between rat snake activity and timing of nest predation seems most consistent with rat snakes locating prey during the day using visual cues but waiting until dark to prey on nests when predation is safer, although designing a direct test of this hypothesis will be challenging.     

Different hunting strategies of generalist predators result in functional differences

The morphological, physiological, and behavioural traits of organisms are often used as surrogates for actual ecological functions. However, differences in these traits do not necessarily lead to functional differences and/or can be context–dependent. Therefore, it is necessary to explicitly test whether the surrogates have general ecological relevance. To investigate the relationship between the hunting strategies of predators (i.e., how, where, and when they hunt) and their function, we used euryphagous spiders as a model group. We used published data on the diet composition of 76 spider species based on natural prey and laboratory prey acceptance experiments. We computed differences in the position and width of trophic niches among pairs of sympatrically occurring species. Pairs were made at different classification levels, ranked according to the dissimilarity in their hunting strategies: congeners, confamiliars (as phylogenetic proxies for similarity in hunting strategy), species from the same main class of hunting strategy, from the same supra-class, and from different supra-classes. As for niche position computed from the natural prey analyses, species from the same class differed less than species from different classes. A similar pattern was obtained from the laboratory studies, but the congeners differed less than the species from the same classes. Niche widths were most similar among congeners and dissimilar among species from different supra-classes. Functional differences among euryphagous spiders increased continuously with increasing difference in their hunting strategy. The relative frequency of hunting strategies within spider assemblages can, therefore, influence the food webs through hunting strategy-specific predator–prey interactions.     

Impact of Gun-hunting on Diurnal Primates in Continental Equatorial Guinea

Bushmeat hunting is threatening wildlife populations across west-central Africa, and now poses a greater threat to primates than habitat loss or degradation does in some areas. However, species vary in their abilities to withstand hunting, either because hunters target them differentially or they vary in their vulnerability to a given level of hunting. We studied the impact of current levels of gun-hunting on diurnal primate species in the little-studied Monte Mitra area of Monte Alén National Park, continental Equatorial Guinea. Most bushmeat is currently trapped, but gun-hunting is increasing as shotguns become more available and affordable, allowing targeting of arboreal as well as terrestrial prey. We collected data over 15-mo, via hunter interviews, gun-hunter follows, an offtake survey recording 9374 individuals, and primate surveys covering 408 km of line transects in 2 sites with differing gun-hunting histories. Inside the park, where gun-hunting pressure was recent and light, we found high primate diversity, density, and biomass, with black colobus (Colobus satanas) particularly abundant at 57 individuals/km². However, around the village, where gun-hunting was longer-established, though other species such as the guenons still persisted (albeit at lower densities), Colobus satanas were virtually absent. Being slow and large-bodied, Colobus satanas are preferred and susceptible prey, and an early indicator of overhunting. Monte Alén National Park is currently an important stronghold for primates, particularly Colobus satanas, but regulation of the trade and enforcement of hunting bans in the park are urgently needed to safeguard their future and that of other vulnerable species. An erratum to this article can be found at