The fossil record of pacas begins in the Oligocene.
Like most rodents, pacas perceive the world through visual, acoustic, tactile, and chemical signals. While generally solitary, they do communicate by means of vocalizations, foot thumping, and tooth grinding. It has been suggested that the hollow chambers formed by their expanded zygomatic arches are resonating chambers to amplify sounds. In captivity, pacas have been observed scent-marking their enclosures with urine and feces.
Communication Channels: acoustic ; chemical
Other Communication Modes: scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
Both paca species are considered lower risk by the IUCN. The main threats to their populations are hunting and habitat destruction.
There are 2 species of cuniculids, placed in the single genus Agouti. These large, terrestrial rodents are commonly called pacas.
Pacas may be agricultural pests in some areas.
Negative Impacts: crop pest
Throughout their range, pacas are much sought for their flesh, which is tender and mild-flavored.
Positive Impacts: food
These plant-eating rodents are primary consumers, and they serve as prey for felids, canids, and reptiles. They likely compete for food with many species that have overlapping diets and habitats, including agoutis (Dasyprocta), squirrels (Sciurus), spiny rats (Proechimys), peccaries (Tayassu), brocket deer (Mazama), tayra (Eira), kinkajous (Potos), coatis (Nasua), woolly opossums (Caluromys), and brown four-eyed opossums (Metachirus). Pacas are parasitized by mites, nematodes, tapeworms, and protozoa.
Commensal/Parasitic Species:
Pacas consume foliage, roots, nuts, seeds, and fruits. Their large cheek pouches may be used in food storage, but this is not certain.
Primary Diet: herbivore (Folivore , Frugivore , Granivore )
Pacas are found in Central and South America, from east central Mexico to Paraguay.
Biogeographic Regions: neotropical (Native )
These rodents live along rivers and streams in tropical forests, from sea level to about 3000 m elevation.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest
Other Habitat Features: riparian
Pacas live 12 to 13 years in the wild, and up to 16 years in captivity.
Pacas are very large, up to around 12 kg in males. Females are somewhat smaller. They have chunky bodies, short, stout legs, hind limbs that are longer than the forelimbs, and a large, blunt head. The eyes are large and external ears are small. Pacas are nearly tailless. The forefeet have 4 functional toes, and the hindfeet 3 (digits 1 and 5 are present but reduced). The claws are thick and hoof-like. The pelage of pacas is coarse and without underfur. Dorsally, pacas are brown, with whitish spots arranged in longitudinal lines. Their bellies are whitish.
The skulls of pacas are unmistakeable. They are broad and massively constructed, with short nasals and long, broad frontals. A sagittal crest may sometimes be found over the posterior part of the braincase. A postorbital process is present, but it seems to be located unusually far back over the orbit. The zygomatic arches are enormously inflated, with jugal and maxillary forming a large, rough-surfaced plate on the outside and a smooth, hollow chamber on the inside. While large, the jugal does not contact the lacrimal. The infraorbital foramen is reduced in size, although these animals are hystricomorphous. A separate canal conducts nerves from the orbit to the rostrum. Pacas have small auditory bullae and long and heavily-built paroccipital processes. Lower jaws are hystricognathous, but the angular process is offset less than in many other hystricognaths.
The cheekteeth of pacas are hypsodont. They are flatcrowned and have a complex pattern of re-entrant folds. The first two molars have 1 labial and 3 lingual folds, while the third molar has 3 labial and 1 lingual. These folds become isolated to form enamel islands as the teeth wear. The dental formula is 1/1, 0/0, 1/1, 3/3 = 20.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
The major predators of pacas are felids, including cougars, jaguarundis, margays, little spotted cats, ocelots, and jaguars. Coyotes are also important predators. Occasional predators include crocodiles, boa constrictors, and bush dogs. Pacas are excellent swimmers and retreat to the water to escape predators.
Known Predators:
No information is available on the mating system of pacas. They are known to be solitary, however, which would suggest that they are polygynandrous.
Pacas breed throughout the year in most of their range. On the Yucatan peninsula, they mate in early winter and females give birth in winter to early spring, which is the dry season. Pacas may have up to two litters per year. Usually only one offspring is born at a time, though twins occur occasionally. The gestation period is about 118 days, after which females experience a postpartum estrus. The young are weaned at 6 to 12 weeks of age. Females begin breeding at one year old.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous ; post-partum estrous
Like all eutherian mammals, female pacas nurture developing offspring through the placenta. After the young are born, they are provided with milk until they are 6 to 12 weeks old. Young pacas are precocial; they are born with their eyes open and they are able to walk shortly after birth.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
