Reproductive biology

Litter size is usually one (exceptionally two). Young are precocial, born furred, and with open eyes. They are able to

A paca (Agouti paca) stands amid fallen leaves. (Photo by © Terry Whit-taker; Frank Lane Picture Agency/Corbis. Reproduced by permission.)

run with the mother from an early age, and they are weaned at around six weeks but may stay with the mother for up to a year afterwards. Gestation lasts between 114-119 days. Interbirth interval is around 190 days. Females generally breed seasonally, but will bear up to three litters if conditions allow. Sexual maturity occurs at between six and 12 months, whenever the weight of females reaches 14.3 lb (6.5 kg) and males reach 16.5 lb (7.5 kg). Where two litters a year occur, the lactation period of the existing young overlaps the female's second pregnancy. Females in breeding condition will exhibit a "frisky hopping" behavior at the approach of the male. This will become more developed if he sprays her with urine. Copulation frequently takes place in water.

Pacas go to considerable effort to reduce the possibility of predation of their offspring. The young is born away from the burrow, in one of the mother's habitual sleeping spots. The morning after its birth, female leads the 22.9-25 oz (650-710 g) young to various holes in the territory. It will choose one with an entrance hole too small for such predators as coatis (Nasua nasua) and tayras (Eira barbara) to enter. The female will bring it leaves and twigs for its nest. Morning and evening, the mother, who is likewise unable to enter this natal burrow, uses a low rolling vocalization to call the young to suckle. Suckling lasts some 90 days, by which time the young paca weighs about 8.8 lb (4 kg). Before it is allowed to suckle, it must defecate and urinate, stimulated to do this when the female licks it. She ingests the resulting products to reduce the possibility of odors around the natal burrow that might attract predators. Thus, pacas have modified the familiar rodent strategy of high numbers, low individual investment into one very much like deer and most other large mammals, which use a strategy of low fecundity but high survivorship. Apart from human hunters, pacas have a large number of other predators, including jaguar, puma, ocelot, margay, jagarundi, bush dog, boa constrictor, and caiman.

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