in groups of five females per male. At present, we have two groups of two females with one male, and two of three females with one male. None of these animals has shown any aggression toward other group members, and all are easier to handle than those raised by their mothers.
It might be expected that denial of a retreat to a naturally burrowing animal would give rise to pathological trauma, but researchers in comparative psychology have shown with other burrowing mammals (Price, 1984) that raising them in cages without any form of retreat causes the animals to mature faster and show less stress than those raised with retreats. Pacas raised without burrows are definitely more tranquil and are also more diurnal, which facilitates observation of their health and behavior. Psychologists have also demonstrated that handling makes an animal’s subsequent behavior toward its handlers less aggressive. The different groups of pacas have been treated according to different regimens, and all are easier to handle than animals left alone. The ease of manipulation is inversely proportional to the age at which they were removed from their mothers. It is hoped that the young born to human-acclimated females will learn their attitudes from their parents.
Pacas born early in the project gained weight at an average rate of 13 grams per kilogram of body weight per day (g/kg bw/day) and reached a weight of 6 kilograms (approximately the weight at maturity) at 18 months. As a result of improved nutrition and a rigorous antiparasite program, those most recently born gained 20 g/kg bw/day, and some have reached 6 kilograms at 4 months. By comparison, cattle in temperate regions gain about 7 to 10 g/kg bw/day during the same age span (Seigmund, 1979).
Pacas are naturally frugivorous. The gathering of wild fruits is not only highly laborious but is also subject to the seasonality of production. Many forest leaves are as nutritious as fruit and may be higher in proteins. One of the benefits of hand-rearing pacas is that they can be taught to eat diets that they would not encounter in the natural state and that adults only learn to eat reluctantly. Experiments are presently under way to develop a diet that consists of a high proportion of easily obtained leaves supplemented with a readily available, aseasonal, high-carbohydrate food such as manioc (Manihot esculentia), which is locally called yucca.
Only a few wild species have been truly domesticated, and most of these have been social species such as dogs and ungulates. Thus, the attempt to domesticate (or even semidomesticate) the paca is faced with long odds. But none of the traditional domestic meat animals thrive in the lowland tropical areas; thus there is a need for a domestic species that will do well in the area. In the 3.5 years since the inception of this project, significant progress has been made.
This 3-year project has several objectives. Using species that are not traditional in Panama, STRI hopes to restore and maintain soil fertility by selecting and establishing highly adaptable, hardy, and competitive leguminous plant species with emphasis on multipurpose shrubs and trees that can be used for green manure, forage, firewood, and timber production; to evaluate the adaptability of potential