The reproductive biology of black-handed spider monkeys (Ateles geoffroyi): Integrating behavior and endocrinology

In this dissertation I report the first study of the reproductive behavior and endocrinology of spider monkeys (genus Ateles) in natural setting. Data were collected from the single group of free ranging A. geoffroyi on Barro Colorado Island (BCI), Panama. A 14-month investigation of the natural history of this group was carried out between November 1997 and December 1998. The BCI spider monkeys have a significantly larger home range size and lower density than spider monkeys studied at other sites. Like all spider monkeys reported to date, the BCI spider monkeys are highly frugivorous and subgroup during the day for foraging. However, unlike other groups, BCI spider monkey females do not maintain core home ranges, and the group often travels as a whole, albeit spread out. The activity budget of the BCI spider monkeys is directly comparable to other spider monkeys.;This study reports the first application of enzyme immunoassay techniques to the genus Ateles. A preliminary study carried out using urine and fecal samples collected from A. geoffroyi at San Diego Zoo, indicates that the technique is applicable, demonstrating parallelism. Feces are shown to be-valid source of estrogen (EIC) and progesterone (PdG) metabolites in this species. Fecal excretion of these metabolites lags behind urinary excretion by 1--2 days.;Behavioral data collected from six females on BCI between February and December 1998 provide a detailed description of spider monkey sexual behavior. A very long average copulation length for this species (approximately 19 minutes) is reported. This is one of the longest among the primates for a single intromission copulatory pattern. Births and conceptions do not conform to a strict seasonal pattern, but appear to be related to food availability and female physical condition at the time of conception.;To investigate the relationship between behavior and female reproductive state I simultaneously collected fecal samples and behavioral data from the six focal females. Grouping patterns were influenced by reproductive state, i.e., pregnant females were observed in larger parties than cycling or non-cycling females. During the peri-ovulatory period, females were recorded in significantly smaller parties.;Results indicate that there are clear differences in the behavior of reproductively cycling and non-cycling females. The former are attacked more by adult males, copulate more, and are generally the targets of place sniffing by adult males more. However, there is no clear association between the stage of a female's cycle and behavior, i.e., female spider monkeys do not seem to have a clear "estrous period". The results are discussed in relation to the concept of "estrus" and its applicability to the anthropoid primates. It is suggested that anthropoid primates have a different form of sexuality from those animals that exhibit clear estrous cycles, and that the term estrus may not be applicable to this group.