Information and the Umwelt: A theoretical framework for the evolution of play.

Play is phylogenetically widespread, and there are many proposed theories and fitness benefits of play. However, we still need a theoretical framework that unifies our understanding of the benefits that facilitated the evolution of play in so many diverse species. Starting with von Uexküll's theory of the Umwelt (i.

Factors influencing terrestriality in primates of the Americas and Madagascar.

Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods.

Dominance and social interaction patterns in brown capuchin monkey (Cebus [Sapajus] apella) social networks.

Strong, stable social bonds in primates are characterized by high levels of social affiliation, low levels of aggression, minimal stress, and affiliative reciprocity within the dyad. In relatively well-studied catarrhine monkeys, these bonds tend to form most frequently between kin, animals close in age, and animals close in rank. This results in patterns of affiliation in which kin, similarly aged animals, and like-ranked animals tend to affiliate and patterns of aggression and submission where animals tend to aggress more toward nonkin and closely ranked animals, and submit more toward distantly ranked animals.

Aggression and social support predict long-term cortisol levels in captive tufted capuchin monkeys (Cebus [Sapajus] apella).

Many nonhuman primates live in complex social groups in which they regularly encounter both social stressors such as aggression and social support such as that provided by long-term affiliative relationships. Repeated exposure to social stressors may result in chronically elevated cortisol levels that can have deleterious physical effects such as impaired immune function, cardiovascular disease, and reduced brain function. In contrast, affiliative social relationships may act as a buffer, dampening the release of cortisol in response to acute and chronic stressors.

Influences of demographic, seasonal, and social factors on automated touchscreen computer use by rhesus monkeys (Macaca mulatta) in a large naturalistic group.

Animals housed in naturalistic social groups with access to automated cognitive testing vary in whether and how much they participate in cognitive testing. Understanding how demographic, seasonal, and social factors relate to participation is essential to evaluating the usefulness of these systems for studying cognition and in assessing the data produced. We evaluated how sex, age, reproductive experience, seasonality, and rank related to patterns of participation in a naturalistic group of rhesus monkeys over a 4-year period.

Use of social network models to understand play partner choice strategies in three primate species.

Although play is seen in many species, its evolutionary function is still largely unknown. Several relevant, proposed hypotheses (such as the training for the unexpected, self-assessment, social skills, and dominance hierarchy hypotheses) make predictions about how animals should optimally choose their play partners based on their familiarity or other demographic variables. We used a social network approach to analyze focal sample data on brown capuchins (Cebus apella), hamadryas baboons (Papio hamadryas), and diademed sifaka (Propithecus diadema) to understand how these species choose their play partners with respect to demographic variables.