Low Levels of Fruit Nitrogen as Drivers for the Evolution of Madagascar's Primate Communities.

The uneven representation of frugivorous mammals and birds across tropical regions - high in the New World, low in Madagascar and intermediate in Africa and Asia - represents a long-standing enigma in ecology. Several hypotheses have been proposed to explain these differences but the ultimate drivers remain unclear. Here, we tested the hypothesis that fruits in Madagascar contain insufficient nitrogen to meet primate metabolic requirements, thus constraining the evolution of frugivory.

Social and personal information use by squirrel monkeys in assessing predation risk.

The threat of predation can significantly influence prey behaviors through altered perceptions of risk. Prey risk perception is constantly updated via collection of personal and social information about predators. Better understanding of the links between information availability, its use, and prey species' perception of risk will aid in explaining how animals adapt to predation.

Primates in 21st century ecosystems: does primate conservation promote ecosystem conservation?

Contributors to this issue of the American Journal of Primatology were among the participants in an invited symposium at the 2008 Association for Tropical Biology and Conservation meeting in Paramaribo, Suriname. They were asked to assess how essential primates are to tropical ecosystems and, given their research interests, discuss how primate research contributes to the broader understanding about how ecosystems function. This introduction to the issue is divided into three parts: a review of the roles that nonhuman primates play in tropical ecosystems; the implementation of large-scale landscape methods used to identify primate densities; and concerns about the increasingly porous boundaries between humans, nonhuman primates, and pathogens.

The ontogeny of handling hard-to-process food in wild brown capuchins (Cebus apella apella): evidence from foraging on the fruit of Maximiliana maripa.

We examined age-related differences in wild brown capuchins' foraging efficiency and the food-processing behaviors directed toward maripa palm fruit (Maximiliana maripa). A detailed comparison of the different foraging techniques showed that plucking the fruit from the infructescence constituted the main difficulty of this task. Foraging efficiency tended to increase with age, with a threshold at which sufficient strength allowed immatures by the age of three to reach adult-level efficiency.

Development of skilled detection and extraction of embedded prey by wild brown capuchin monkeys (Cebus apella apella).

Brown capuchin monkeys (Cebus apella apella) in Suriname forage on larvae enclosed within healthy bamboo stalks. We applied the searching versus handling dichotomy of optimal foraging models to highlight developmental processes contributing to foraging on embedded prey. Larvae acquisition begins with search; selecting an appropriate stalk and locating the embedded larvae; followed by handling, ripping the stalk open, and extracting the larvae.

Possible fruit protein effects on primate communities in madagascar and the neotropics.

Background: The ecological factors contributing to the evolution of tropical vertebrate communities are still poorly understood. Primate communities of the tropical Americas have fewer folivorous but more frugivorous genera than tropical regions of the Old World and especially many more frugivorous genera than Madagascar. Reasons for this phenomenon are largely unexplored.

Allelic variation in the squirrel monkey x-linked color vision gene: biogeographical and behavioral correlates.

Most Neotropical primate species possess a polymorphic X-linked and a monomorphic autosomal color vision gene. Consequently, populations are composed of both dichromatics and trichromatics. Most theories on the maintenance of this genetic system revolve around possible advantages for foraging ecology.

Patterns of individual diet choice and efficiency of foraging in wedge-capped capuchin monkeys (Cebus olivaceus).

Capuchin monkeys (Cebus olivaceus) exhibit extensive intragroup variability in foraging and diet. To consider how age, sex, and individual identity contribute to this variability, the authors examined foraging and diet in 18 wedge-capped capuchin monkeys in 1 social group in the wild. Age-sex classes did not differ in the time spent ingesting food, the reliance on plant foods, the foraging actions used or substrates exploited, or in the efficiency of exploiting animal foods.

Temperament in nonhuman primates.

Formerly applied to studies of responsivity in children, in more recent years the concept of temperament has been applied to nonhuman primates at the individual, species, and now population levels. While the concepts of temperament and personality have been less distinguished in nonhuman primate studies than in the human literature, temperamental and personality differences have now been identified among individual primates and among primate species in a number of studies. At the individual level, certain temperamental characteristics have been associated with age, sex, and most frequently rank.

Wild squirrel monkey (Saimiri sciureus) "caregiver" calls: Contexts and acoustic structure.

A field study of the vocal behavior of 22 wild adult female squirrel monkeys (Saimiri sciureus) in Parque Nacional del Manu, Peru, found that 21% of vocalizations were "caregiver" calls. Caregiver calls are brief, low frequency calls, often with numerous harmonics, that are addressed by caregivers to their own infants in three contexts: 1) prenurse, signalling the caregiver's location and willingness to nurse; 2) nurse, while nursing; and 3) end nurse, indicating the end of the nursing bout. Three measures (start, end, and peak frequency) of the acoustic structure of the fundamental frequency of the caregiver calls significantly differed across the contexts.

Interleukin-1 induces sleep-like behavior and alters call structure in juvenile rhesus macaques.

To date, there have been no investigations of the behavioral effects of interleukin-1 (IL-1) in nonhuman primates. In this study the locomotor behavior and vocalizations of juvenile rhesus monkeys were monitored for 45 minutes following intravenous injections of recombinant human IL-1 alpha. In addition, their reaction to a broadcasted recording of infant monkey distress calls was determined 20 minutes after the beginning of each test session.

Male residence and association patterns in Costa Rican squirrel monkeys (Saimiri oerstedi).

A model is developed to interpret the evolution of the unusual pattern of male residence and social structure in the Costa Rican squirrel monkey (Saimiri oerstedi). Observations of a wild population document that males 1) maintain close spatial and social associations with other males, especially other males in their birth cohort, but not females and infants; 2) exhibit negligible within-troop male-male aggression, high levels of antipredator vigilance, and frequent predator deterrence; 3) cooperate in aggressive olfactory investigation of females; and 4) maintain residence in their natal troop with their male birth cohort, eventually succeeding to reproductive positions in their natal troop. Less commonly, male age-cohorts leave the troop well past reproductive maturity and usurp the reproductive male cohort in another troop.

Vocal coordination of troop movement among white-faced capuchin monkeys, Cebus capucinus.

Coordinated travel by social groups is well documented, often with evidence that cognitive spatial maps are employed. Yet the mechanisms by which movement decisions are made and implemented within social groups are poorly known. In a field study of white-faced capuchin monkeys in Costa Rica it was demonstrated that a specific call, the "trill," is used by adults in the initiation and directing of troop movement.

Predation by squirrel monkeys and double-toothed kites on tent-making bats.

Central American squirrel monkeys (Saimiri oerstedi) appear to recognize the modified leaves that phyllostomid bats utilize for diurnal roost sites. The monkeys visually and manually search these bat tents for both bats and insects. Adult males are the most successful at capturing bats.