The role of Cayo Santiago in primate field studies.

Cayo Santiago has provided the opportunity to study primate biology in a free-ranging neutral environment free of provocative human influences. Rarely, if ever, does such a situation occur in natural rhesus habitats in Asia. This Cayo Santiago advantage has permitted fine-scale analyses of the details of behavior, ecology, reproduction, genetics, demography, and pathobiology with a greater degree of precision than is possible in the field. At the same time, research on Cayo Santiago has provided valuable baselines for comparative work with natural populations in Asia. Field and laboratory work with the Cayo Santiago colony has produced an impressive number of pioneering studies, from the first investigations of Carpenter in the late 1930's, to the recent demonstrations of Kessler and Rawlins on the demographic role of tetanus in rhesus population ecology and the effectiveness of an inoculation program in eliminating infectious disease. Few, if any, primate colonies have had such a productive interface of naturalistic studies of behavior and ecology with basic biomedical research.

Population survey of macaques in northern Sulawesi.

A field survey of 25 sites in Sulawesi Utara (north Sulawesi) in 1987 and 1988 found macaques in 16 of these sites. The most viable population of Macaca nigra was found in the Tangkoko reserve at an estimated density of 76.2 monkeys/km2, which is less than one-third the abundance reported in the late 1970s by the MacKinnons. The adjacent reserves of Batuangus and Duasudara had only 22 monkeys/km2, yielding a population estimate for these three contiguous reserves of only 3,655 individuals. Maccaca nigrescens were found in the central and western portions of Dumoga-Bone National Park in densities of 15.5 and 16.4 monkeys/km2, significantly below the density of 27/km2 reported by the MacKinnons. The more peripheral areas of Dumoga-Bone had only 8.15 monkeys/km2, yielding a population estimate of M. nigrescens in Dumoga-Bone of less than 34,000. Our total population estimate for M. nigra and M. nigrescens combined is less than 50,000 individuals, which is considerably below that reported in recent litreture. M. hecki were observed in only two locations, Tangale and Panua Reserves, at low densities of 3.3 to 5.2 monkeys/km2, suggesting its range and abundance have declined since the observations of Groves (pp. 84-124 in THE MACAQUES: STUDIES IN ECOLOGY, BEHAVIOR AND EVOLUTION. D. G. Lindburg, ed. New York, Van Nostrand Reinhold, 1980). Several factors have contributed to population decline in these species: habitat shrinkage, increasing human population pressure, and drought conditions. Group sizes were significantly smaller in our study than in previous ones, and we found a shortage of juveniles and infants.

Growth of pika in laboratory confinement.

Captive-born pikas (Ochotoma princeps) from 13 litters were maintained for up to three months in a laboratory setting. Mean litter size was 2.69 +/- 0.75, with litters of three the most frequent, and representing 68% of all litters observed. Mean individual birthweight was 11.7 g with a range of 8.8 to 16.8 g. Weights were taken every other day from birth, which yielded a growth curve equation of y = 12.18 + 1.72x. There was a strong positive linear correlation between bodyweight and time (r = 0.98, P less than 0.001), and a significant difference was noted between sexes, with females the heaviest. Subjects reached adult weight within 3 months. These data represent the first reports of growth in this species, and indicate that pikas are among the fastest growing species within the order Lagomorpha.

Natural regulation of rhesus monkey populations in Kathmandu, Nepal. Rhesus monkey groups near Kathmandu, Nepal, show demographic patterns of intrinsic population stability.

In Kathmandu valley, two populations of rhesus monkeys which are totally protected, have shown relatively stable numbers over a period of several years. Population stability within heterosexual troops appears to have been maintained through lower birth rates and slightly higher infant and adult mortality rates than in comparable rhesus populations in India which have been subject to trapping. Although the behavioral and physiological mechanisms by which these demographic changes occur are not known, behavioral observations on these populations suggest several possibilities. These data represent the first indication of possible mechanisms for population regulation in natural rhesus populations.

Effects of parental environment on the prevalence of convulsive seizures in Onychomys torridus.

Male and female southern grasshopper mice (Onychomys torridus) were reared in 1 of 3 different parental environments: (a) with the natural male and female parents; (b) with the female parent only; or (c) with foster parents of a closely related species, Peromyscus leucopus. All mice were weaned at 25 days of age, then observed individually in an open field arena at 10-day intervals from 30 to 100 days of age. Twenty-seven of 59 subjects (45.8%) that were reared by the natural parents exhibited convulsive seizures during at least 1 of the 8 tests in the open field arena. The prevalence of convulsive seizures increased significantly in subjects that received altered parental care: 27 of 41 subjects (65.9%) reared by the female parent only or by Peromyscus foster parents seized during at least 1 of the 8 tests in the open field. Subjects from the 3 treatment groups did not differ in the mean number of seizures observed during the 8 open field tests. These results demonstrate a significant influence of the preweaning parental environment on the prevalence of convulsive seizures on Onychomys torridus.

Effects of artificial feeding on aggressive behaviour of rhesus mondeys in India.

Artificial feeding of rhesus monkeys (Macaca mulatta), which provides the major food source for most rhesus groups in rural and urban habitats, is common practice in India. Such feeding results in significant increases in aggressive competition within the monkey groups: during feeding periods the frequencies of aggressive threats, chases, and attacks increased two to six times above those of non-feeding periods in each of eight different groups. Fighting behaviour did not increase in most groups studied, but did show a rise in one large urban group in Calcutta. The implications of these results for the management of primate breeding colonies are discussed.

The development of convulsive seizures in the grasshopper mouse (Onychomys torridus).

Open-field tests were administered to 29 male and 50 female southern grasshopper mice (Onychomys torridus) at 10-day intervals from 30-100 days of age. Convulsive seizures were observed to occur in 9 males and 23 females during at least 1 of the open-field tests. No significant differences appeared in the seizure characteristics of male and female subjects. The potential of O. torridus as an animal model of human epilepsy is discussed.