Zoo Ecology of a Primate Species: Squirrel Monkey (Saimiri sciureus)

Abstract

Understanding how captivity affects the behavioral and development traits of a species is important for management and conservation in zoos. The ecology of squirrel monkeys (Saimiri sp.) may be different in captivity than in their natural environment. I investigated five common ecological aspects: reproduction, vigilant behaviors, life history traits, and generational changes in seasonality. Reproduction in squirrel monkeys is naturally seasonal with speculation as to the environmental factor with the greatest influence. In captivity, different types of habitats used to house squirrel monkeys may affect seasonality of reproduction. Those individuals housed in outdoor enclosures maintained a seasonal peak of births while those monkeys kept in indoor enclosures reproduced throughout the year. These habitat-based differences in reproduction allowed for analysis of environmental variables, and temperature had a large impact on births.

Captivity also provides the opportunity to determine whether differences exist in vigilant responses of individuals to playbacks of alarm calls, in regards to whether anti-predator responses are innately predisposed or require experience. Captive squirrel monkeys presented with alarm, predator, and control sounds elicited a greater amount of vigilant behaviors to alarm calls compared to other sounds. However these behaviors were not maintained for a minute after the playback. Interestingly, a “group personality” seemed to be exhibited; responses were not related to group size or type of enclosure. Captive squirrel monkeys were naïve yet still able to correctly respond to alarm calls by displaying vigilant behaviors. Differences due to captive environments may affect life history traits of squirrel monkey populations. Variation in life history traits occurs between sexes, zoos, and generations of squirrel monkeys maintained in captivity. Prospective analyses predict that juvenile and adult survivals have the greatest impacts on population growth. Fertility, however, is the demographic trait that contributes the most to changes in population size based on a retrospective analysis. The seasonality of reproduction has previously been shown to vary depending on type of habitat. With several generations of squirrel monkeys established in captivity, change in reproduction timing allowed for testing of whether this change is due to plasticity or selection. Using pedigree data, differences between when mothers and daughters have their offspring reflects environmental influences, rather than heritability. Seasonal reproduction is significantly different between the wild and captive generations, however not between the two captive generations.