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Kinkajous (Ph.D. Research)

I studied Kinkajous for my PhD at the University of Tennessee and the Smithsonian Tropical Research Institute. I continue to have an interest in the ecology and evolution of kinkajous and their relatives. The text below summarizes my main findings on kinkajous. Additional pictures and information are available the National Geographic Magazine article covering my research.

Twisted into the double helix of DNA within Potos flavus lies the truth - the kinkajou is not a monkey. Little else about this animal betrays its taxonomy. Indeed, after judging the prehensile tail, big forward facing eyes and propensity for fruit, early taxonomists declared the kinkajou a primate, and gave it the binomial name Lemur flavus. More thorough anatomical and genetic studies uncovered the true Carnivoran ancestry of the kinkajou. Dental morphology and fur on the sole of their feet gave early clues that kinkajous were not primates. Later, DNA sequences confirmed that they are in the order Carnivora, and the kinkajou was rightfully placed with coatis, raccoons, and ringtails in the family Procyonidae.

In some ways, the kinkajou is more monkey-like than many monkeys. Its tail is more prehensile than most, it never ventures the ground, and it eats more fruit than any primate on record. The fabulous muscular tail of a kinkajou gives this medium sized (2-4kg) mammal confidence to travel from tree to tree in the unlit greenness of the neotropical night. It is used as a safety line, latched to secure branches behind as the animal scampers forward down dark branches. Kinkajous also hang inverted by their tail while using their dexterous forepaws to manipulate food.

The security offered by this tail, and the dangers of the forest floor at night, keep the kinkajou in the tree canopy. They almost never go to the ground and are rarely found in the diet of terrestrial predators such as jaguars or the traps of grounded biologists. In fact, the combination of traits embodied in the kinkajou make it a rare meal for any predator. They are too nocturnal for eagles, too large for neotropical forest owls, and too arboreal for potential mammalian predators. This low predation risk is evident not only in their fearless unconcern with terrestrial human observers, but also in their low reproductive rate and indifference to moonlight. Female kinkajous typically have a liter size of one, and give birth no more than once per year. Clearly, a species with such a slow reproductive rate can not survive a high predation rate, yet most neotropical forests are teeming with kinkajous. Many nocturnal predators are more effective hunters with the help of bright moonlight, forcing their prey species to be less active when the moon is out. However, kinkajous do not shy away from moonlight, further suggesting that they have few predation worries.

Kinkajous aren't just in the trees to avoid predators, they're up there for the food. Despite their carnivoran ancestry, kinkajous are one of the most frugivorous mammals known and feed by plucking ripe fruit off canopy trees and vines. Over one year the diet of a population of kinkajous consisted of 90% fruit, with the rest leaves and nectar. These Panamanian kinkajous ate no animal prey, although records from other parts of their range suggest that insects may sometimes be an important food. Kinkajous eat a wide variety of fruit species (at least 78 in central Panama) and they prefer fruits that are fleshy and sweet.

This extreme frugivory and low predation risk set the scene for the evolution of a unique social organization in this unusual carnivore. Low predation risk reduces the security benefits of constant group living, yet the distribution and abundance of fleshy fruit in tropical forests is thought to promote social life. The solution that has evolved in kinkajous is a solitary group life that converges with primates of similar ecology.

Freed up from the need for continual group living, kinkajous typically forage alone at night, like most carnivores, but still regularly meet up with other members of their social group, like many primates. This solitary group life is an adaptation to reduce feeding competition. Three kinkajous in a small tree will polish off the available fruit three times as fast as a solitary animal, and will therefore have to visit three times as many trees. Very large fruiting trees have such stupendous fruit crops that competition isn't as important, and these are the sites where kinkajou group members often reunite – sort of a picnic in the trees. Social groups also convene at day dens. Between dawn and dusk kinkajous seek refuge inside tree holes or thick palm fronds, and up to five animals will squeeze into one of these hideouts. Once reunitedwith the group, kinkajous show a range of social behaviors including allogrooming, group feeding, and play with juveniles.

Although kinkajou social groups are based on a family unit, it's not your typical animal clan. In addition to a breeding female with her juvenile (<1 y old) and subadult (2-3 y old) offspring, the groups contain two adult males. These males can be related, although this is not always the case. They are generally amicable towards each other, but occasionally squabble, especially around breeding time. One male dominates these brief fights and gets most of the copulations. Inheritance of kinkajou social groups may be patrilineal since males are the more social sex and dispersal is female biased. Not all females join these social groups, and some raise offspring apart from a group structure as ‘single moms'.

Adult kinkajous have home ranges of about 30-50 ha and apparently have strict territorial boundaries, as individuals from different social groups do not overlap. Kinkajous have a unique set of scent glands on their chin, throat, and chest that are probably used to mark territorial boundaries. ‘Single mom' kinkajous are not group members, but live along the borders of neighboring social groups and overlap slightly with the group males, but never with the group females. The precise reason that pairs of males coexist in one social group is not entirely clear, but may be related to the costs of marking and defending a territory large enough to completely contain one group female and also overlap partially with at least one ‘single mom'.

This flexible group structure, male-male sociality, and female dispersal is unknown from other carnivore species, however, it is found in spider monkeys and chimpanzees. These species are much more social than kinkajous, with larger groups and more interaction, but they share some of the same core social characteristics: fission-fusion groups, male sociality, and female biased dispersal. They also share important ecological traits with kinkajous, these are two of the most frugivorous primates and both have relatively low predation risk. Thus these species have converged on similar evolutionary solutions to an arboreal, fruit-eating, low predation lifestyle. Given these similarities, it's easy to see why early naturalists mistook the kinkajou for a primate, and why local people still refer to it as "mono de la noche" or monkey of the night.

Kays, R. (2003). Social polyandry and promiscuous mating in a primate-like carnivore: the kinkajou (Potos flavus). In Monogamy: mating strategies and partnerships in birds, humans and other mammals.: 125-137. Reichard, U. H. & Boesch, C. (Ed.). Cambridge, UK: Cambridge University Press.

Kays, R. W. (2000). The behavior of olingos (Bassaricyon gabii) and their competition with kinkajous (Potos flavus) in central Panama. Mammalia 64: 1-10.

Kays, R. W. (1999). Food preferences of kinkajous (Potos flavus): A frugivorous carnivore. Journal of Mammalogy 80: 589-599.

Kays, R. W. (1999). A hoistable arboreal mammal trap. Wildlife Society Bulletin 27: 298-300.

Kays, R. W. & Gittleman, J. G. (2001). The social organization of the kinkajou Potos flavus (Procyonidae). Journal of Zoology 253: 491-504.

Kays, R. W., Gittleman, J. G., & Wayne, R. K. (2000). Microsatellite analysis of kinkajou social organization. Molecular Ecology 9: 743-751.

Kays, R. W. & Gittleman, J. L. (1995). Home range size and social behavior of kinkajous (Potos flavus) in the Republic of Panama. Biotropica 27: 530-534.

Kays, R. W. (1999). The Solitary Group Life of a Frugivorous Carnivore: Ecology, Behavior and Genetics of Kinkajous (Potos flavus). ( edn). Knoxville, Tennessee: The University of Tennessee, Knoxville.