howler monkey eating in a tree


by Jacalyn Giacalone, Ph.D.

Posted in: Mammal Directory, Rainforest Connection Live

Pacas are reddish brown with three or four rows of white spots that may form stripes along the sides of their bodies. They have very short tails and large heads with big cheeks. They weigh about 9 kg and look like a larger, heavier version of the basic agouti body plan. They look rather piglike in the season of abundant fruit supply because they store up body fat and then live off this fat, supplemented with a diet of leaves, in the season of fruit shortage (November to March).

Pacas do not climb and therefore live on the forest floor, where they are dependent on arboreal mammals to knock fruit from trees. However, they have a number of special adaptations that suit them to their lifestyle and so they have flourished in a large geographic area. They are found in a variety of forests from southern Mexico to southern Brazil. Their meat is prized by hunters throughout their range. In Panama they are called conejo pintada, and are endangered in some localities because of over-hunting.

Pacas eat fruits, and, unlike agoutis, they do not rely on large, hard seeds, but prefer soft, sweet pulpy fruits. They also browse on leaves and seedlings, depending on these less digestible foods in time of fruit shortage. They have a specialized digestive tract with an elongated large intestine that is adapted for leaf digestion through bacterial fermentation. They produce special feces that they eat and re-digest to derive greatest benefit from the nutrients (much as rabbits do).

They generally live in pairs but forage alone and den in separate burrows. Burrows usually have several entrances, some of which are camouflaged with leaves. One pair of adults occupies an area of about 3 hectares.

It is usually necessary to go out in the forest at night with bright lights in order to see pacas. They are nocturnal, usually appearing about the time when agoutis go to sleep. They have bright eyeshines that are widely spaced and bright orange to yellow in color. They are usually very quiet, but will walk noisily on dry leaves. They also have very deep voices that they use in social gatherings, where they may make grunting noises or stunningly loud barks. Very complex cavities in the cheek bones of their skulls are thought to act as resonating structures for these vocalizations. We have heard them congregate under Smith House when a jack fruit tree (no longer there) was dropping ripe fruits. The pacas made noises like a party of people laughing with deep throaty laughs.

Pacas require water for breeding, according to Dr. Nicholas Smythe, who raised and developed a domesticated non-territorial version of paca, and studied their life history on BCI and nearby Gigante Peninsula. Young pacas are most likely to die in the season of fruit shortage from November to March. Perhaps they are more easily taken by predators because pacas must spend longer hours foraging for food and may be in poorer condition in this season. Adult pacas live about 3.5 years on the average on BCI, but can live more than 7 years in captivity.

© Jacalyn Giacalone, Ph.D. 1997