None of the discussion above obviates the fact that primates are a frequent prey item for many species of wild cats. (The frequency in which primates occur in leopard diets ranges as high as 80%.)36 And, as we've said before, if we want to project what might have happened to our early ancestors, we can look at modern non-human primates that end up as prey for the big cats. Normally opportunistic hunters, the availability of prey or total prey numbers are the important criteria for food selection by cats. In other words, most cats are not searching out a specific kind of food. They hunt and kill what they encounter, and the more prey of one species in their neighborhood, the more likely the cats are to encounter an individual of that species.37
Leopards have a wide geographic range over much of Africa and southern Asia. Particularly flexible in their environmental needs, they are able to exist in almost any habitat, from arid grassland to semi-desert to dense rain forest, and from mountainous foothills to riverine habitat. The hunting strategy of the leopard is largely a matter of lurking in likely places (water holes are always good) and approaching its prey in a stealthy manner, followed by a quick spring and swipe with the paw. (It has been noted that when capturing primates a leopard will grab ahold wherever possible rather than grabbing only for the neck as it would if capturing a herbivore; primates are obviously a little more agile than a buffalo.) The use of stealth by hunting leopards cannot be overstated. Leopards are adept at silently creeping up on sleeping animals; baboons asleep in rocks are a frequent prize of nocturnal hunting. So ghostly silent is the hunting leopard that humans and dogs have been killed in their beds without waking others in the house. The famous naturalist, Jonathan Kingdon, wrote about one specific case in which a human baby was taken off the breast of its sleeping mother by a leopard.38
Leopards feed on relatively small prey, such as primates, because they hunt alone and need to carry carcasses into trees to keep their kills from being pirated away by larger cats or pack-hunting dogs and hyenas. Leopards also have a much wider prey base than other large cat species,
which enables them to utilize primates of all sizes in their diets. Consequently, the range of non-human primate species in the diet of leopards is rather extensive. In Africa they are known to prey on bonobos (pygmy chimpanzees), common chimpanzees, western lowland gorillas, many species of rain-forest guenons, vervets, and species of savanna and forest baboons. In Asia leopards prey on langurs, golden snub-nosed monkeys, a range of macaque species, and gibbons.39
The proportion of primate prey in the diet differs greatly among species of cats, but leopards commonly consume primates throughout their extensive range. During a classic study of leopard ecology in Côte d'Ivoire, Bernard Hoppe-Dominik discovered that seven different species of primates accounted for about l6% of the prey in the diet of leopards. Based on analysis of leopard feces, George Schaller found that Hanuman langurs composed almost one-third of leopard diets at a site in India. Researchers reported one of the highest frequencies of primates in a leopard diet (about 82%) at another research site in India. Primatologist Lynne Isbell found that an influx of leopards caused such an escalation in vervet deaths at Amboseli National Park, Kenya, that nearly half the vervet population she was studying was killed during a 1-year period. One last example—an absence of deer and antelope (possibly due to poaching) in Indonesia's Meru-Betiri Park converted both tigers and leopards to reliance on primates as their primary prey. John Seidensticker of the Smithsonian Institution, along with Ir. Suyono of the Indonesian government, estimated that the percentages of primates in tiger and leopard diets totaled 33% and 57%, respectively.40
The clouded leopard of Southeast Asia (a separate species that is different in its anatomy and is much smaller than the true leopard) is one of the most arboreal of the cat family. It is intermediate in appearance between the large cats of the genus Panthera (leopards, lions, tigers) and the small cats of the genus Felis (ocelots, caracals, bobcats). With a relatively small head and yet with large canines and muzzle, the clouded leopard is supremely efficient in the capture of primates. Clouded leopards have been known to prey on large primates such as juvenile orangutans and proboscis monkeys.41
One species of wild cat, the cheetah, might be considered an implausible predator in comparison to other members of its family. Of all cats only the cheetah has no sheath into which its claws can retract. (Precisely speaking, it is not that they are unable to retract their claws, there is simply no skin into which the claws can be drawn.) The cheetah also exhibits smaller canines and larger nostrils than other large-cat species, and they differ radically from other cats in their hunting techniques as well. Unlike the other cats, cheetah bodies are geared for high-speed pursuit of prey and not for stealthy ambush. Cheetah prey are smaller in size than that of lions or leopards, and their unusual claws make them completely terrestrial. Compared to the other large cats, few records exist of cheetah predation on primates.42
Tigers are solitary, territorial hunters that thrive in dense vegetation where their camouflage stripes almost totally hide them from prey. Stripes serve to break up the tiger's silhouette in long grass, thus giving the species a great advantage during the stalking phase of the hunt. Tigers are usually assumed to take only huge prey (for example, water buffalo that weigh in excess of 800 pounds), but tigers—like all cats—are opportunists, and a smallish primate is often a quick and satisfying meal. Tigers have been identified as predators of Hanuman langurs, orangutans, and many of the Asian macaque species.
Leaf-eating langurs are one of the major prey species of tigers in the forest of Ranthambhore, India, where tigers catch these partly terrestrial monkeys when they descend to the ground. Although langurs are a regular part of the tigers' diets in the Ranthambhore study, finding a langur carcass is rare because a 25-to-40-pound monkey is consumed completely by a tiger at one feeding. Fecal samples gathered in Royal Chitwan National Park, Nepal, confirmed the inclusion of langurs in the tiger diet there, and at Kanha, India, langurs and rhesus monkeys are commonly captured by tigers.43
All cats are solitary hunters except lions. In his monograph on Serengeti lions, zoologist George Schaller calculated that lions paired up with at least one other pride member in slightly over half of their hunts. However, the number of prey killed per lion per hunt actually decreases when more than two lions are hunting together. Benefits of group living must accrue to female lions through the maintenance of territories and protection of young, because the foraging benefits of social hunting for lions are not sufficient to account for the formation of groups.
Lions begin their hunt by randomly searching their environment for prey. Once prey has been sighted, the stalk phase of the hunt can be of varying length, alternating between crouched movements and frozen stillness. If the prey animal remains unaware of the stalking lion, the predator will make a final, fast, and deadly dash. At several African sites, fecal analyses showed a low range of primate prey in lion diets (near zero to 6%).44 However, we know from personal experience that some lions actually may come to prefer primates.
We had the opportunity to observe two lions that were practically baboon connoisseurs. Todd Wilkinson, guide at Rukimechi Reserve near Mana Pools National Park, Zimbabwe, had told us of two lionesses whose favorite prey was baboons. Todd was so familiar with the wildlife of the private reserve that he found the two lionesses lying in a dry riverbank within an hour. They were the only two in the pride who had a predilection for primate prey. Todd had witnessed two kills himself and explained that the "girls" had started preferring baboons at an early age and kept up the habit as they grew older.45 Six sightings of baboon kills by the two lionesses were recorded in a four-year period. Given the rarity of seeing a lion kill, this was an impressive number.
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