No abstract

Data obtained during a field study of two species of nonhuman primates (Alouatta villosa and Ateles geoffroyi) living in the Tikal National Park in Guatemala are used to suggest an answer to the question: To what extent is the existence of a particular form of social organization (group size, structure, and composition) an indication of the amount of energy in the form of food resources available to animals in a particular habitat? Seven researchers working in teams spent 2,318 hours in the field, 1,145 hours of which were in contact with the monkeys. Comparisons of dietary data, estimated energy expenditures, and habitat productivity provide indications of the degree to which a habitat is capable of supporting the energy and other nutritional requirements of howler and spider monkeys living within the study area. These data suggest that much larger populations and different forms of social organizations can be supported by resources available within the habitat.

ABSTRACT. Three techniques of observing spider monkeys, Ateles geoffroyi, in the lowland rain forest of Guatemala at the archeological site of Tikal included shadowing animals, observations by a stationary observer above the canopy, and seven-observer "picket lines." Results indicate (1) total party size in shadow data is larger and probably more representative than that recorded by both stationary methods, (2) the relative proportions of monkeys in the five age/sex classes do not statistically differ among the three techniques, (3) picket line observations permit most accurate age/sex identification, and (4) the adult male: adult female ratio is 36:64.