From June through November 1990, behavioral and demographic information was collected on 16 groups of free-ranging moustached tamarin monkeys inhabiting Padre Isla, a small island (5.2 km) in the Amazon Basin of northeastern Peru (S3º44', W73º14'). The island is of relatively recent origin, formed approximately 100 years ago from alluvial sediments deposited by the Amazon River. The area is a protected ecological reserve and includes a permanent research station maintained by the Proyecto Peruano de Primatología. Although mammalian predators, except for domesticated dogs, are absent from the island, constrictors, poisonous snakes, and birds of prey represent significant predatory threats to the tamarins [Heymann, 1987].
Moustached tamarins are not native to Padre Isla. In 1977, 1978, and 1980, researchers from the Proyecto Peruano de Primatologi4 (PPP) and the Ministerio de Agricultura y Alimentación wild-trapped and released 20 S. mystax groups on the island (87 animals) for purposes of research and study. Individuals were sexed, aged, permanently tattooed, and fitted with collars for later field identification. All members of an original wild-trapped group were taken to a particular location on the island, placed in a large outdoor holding cage, and released simultaneously. From 1980 to 1989, the PPP conducted periodic visual and trap censuses of Padre Isla's moustached tamarin population. General information on the vegetation of Padre Isla,and the behavior and ecology of the island's tamarins can be found in Moya et al. [1980], Garber et al. [1984], and Norconk [1986].
In 1990 we began a study of moustached tamarin mating systems by retrapping and recensusing the population. The procedure used to capture the animals involved habituating an entire group to a baited trap site composed of a single large cage divided into 10 separate compartments, each with its own manually operated door. The compartments were closed by pulling a string that runs from each door to the blind constructed some 5 meters from the trap. Although more labor intensive than using spring-loaded traps, this method of waiting in a blind and manually closing or opening each door independently has four primary advantages:
1) observation of the group from inside the blind prior
to trapping enables the researcher to determine how many animals are in the
group and whether all of the animals have entered the traps to feed;
2) the doors are closed silently and other group members are unaware that an
individual has been captured;
3) the entire group can be captured in a single day (often in the span of 1-2
hours);
and 4) since the animals are unaware of the presence of the researcher, the
technique can also be used to monitor changes in the composition of marked groups.
Immediately after capture, the group was transported to the field laboratory. Each individual was injected intramuscularly with 0.1-0.15 cc of ketamin HCL (a tranquilizer) and 0.05 cc of torbutrol (an analgesic). The tamarins were examined, measured, weighed, marked with a permanent tattoo, and fitted with an identification collar. Impressions were made of the maxillary and mandibular dentition of each moustached tamarin. Individuals were then assigned to general age categories (i.e., infant, juvenile, subadult, and adult) based on dental development, relative degree of dental wear, and dental stain according to criteria established by Soini and Soini [19821.
Subadults were defined as individuals with all permanent teeth erupted but with canines still not in full occlusion (approximately 12-18 months of age). Adults were defined as individuals with all permanent teeth in full occlusion. The adult category was subdivided into age classes based on the relative amount of stain and wear visible on the incisors and the cusp tips of the canines. Three grades of wear were noted. The Adult 1 (Al) class exhibited unstained (white) teeth and virtually no evidence of dental war, the Adult 2 (A2) class exhibited moderate dental wear (minimal dentin exposure) and slight staining, and the Adult 3 (A3) class was characterized by extreme wear (canines broken, heavy dentin exposure on incisors) and heavy staining. Based on a comparison with 19 animals of known age in the population (e.g., an animal trapped as an infant in 1986 would be 4 years old in 1990), Al adults are estimated to be 2-4 years of age, A2 adults 4 -8 years of age, and A3 adults 8 + years of age. Adult females were scored as pregnant, lactating, or nonreproductive. Pregnancy was determined by uterine palpation. Lactation was determined by the presence of milk in the mammary glands.
Age and sex differences in weight and other body measurements were compared using a Student's t-test.
