No abstract

We describe two cases of infanticide, two suspected infanticides, and a forced copulation by familiar resident males in two populations of wild spider monkeys (Ateles belzebuth chamek and A. geoffroyi yucatanensis). These are the first known infanticides and forced copulation in spider monkeys. Data were gathered from four neighboring communities of spider monkeys in Manu National Park at the Cocha Cashu Biological Station, Peru and two communities in the Otoch Ma'ax Yetel Kooh Reserve at Punta Laguna, Mexico, during intensive field studies of over 2,000 hr each. These are rare behaviors, but results suggest that mating history and sexual coercion are important in spider monkey social relationships.

I investigated the mating system and male mating tactics for a population of wild spider monkeys (Ateles belzebuth chamek), to identify the behaviors males used to achieve and maintain access to sexually receptive females, and to examine if some males used more tactics than other males and/or had differential access to females. Results show that the mating system mostly involved scramble competition polygyny and that males used a range of mating tactics and behaviors, previously unreported for spider monkeys. The most unusual feature of spider monkey mating behavior was the secretive nature of copulations-nearly all copulations were clandestine, but a few were in the presence of other group members. Fifteen sexually mature males were observed to copulate 43 times. These data provide the first opportunity to evaluate how female availability influences male-male competition. First, the operational sex ratio was highly skewed toward males because usually only one female was receptive in each community per month. Second, females only mated with a few males in their community in any one mating period, but some females mated over the course of multiple consecutive mating periods, eventually mating with most or all of the males in their community. Across all communities, 9 (21%) of the 43 copulations involved a single male-female partner, 20 (47%) involved four males mating with the same female, and males mated with from one to four different females. Fourteen of the 16 total adult males and 1 subadult male (10 total) copulated. One or two males in each community were successful in monopolizing access to receptive females, and these males did not usually have the highest rates of copulation. In this system, clandestine copulations are one behavioral solution to the complex problem of gaining mating exclusivity and, probably, exercising mate choice.

El presente trabajo pretende establecer la prevalencia de los helmintos intestinales de una poblaciónprotegida de Ateles belzebuth chamek. Para ello, se colectaron muestras fecales de 34 individuos pertenecientes a tres grupos sociales de una población en la Estación Biológica Cocha Cashu del Parque Nacional del Manu, Perú. Las muestras fueron fijadas en formol (10 %, 60 ºC) y analizadas mediante el método directo y el de Ritchie para el caso de helmintos. Para los protozoarios, las muestras se conservaron en alcohol polivinílico (PVA) y fueron procesadas para su análisis mediante frotis y tinción con colorante Tricrómica de Gomori. El análisis de laboratorio reveló que 76,4 % (26/34) de los individuos muestreados estaban parasitados. Se identificaron larvas o huevecillos de Strongyloides, Trichuris, Trypanoxyuris, tipo estrongilídeo y de un tremátodo de la familia Dicrocoeliidae, pero de acuerdo con las técnicas empleadas no se halló ninguna especie de protozoario.