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All mammals thus far studied sleep, yet important questions remain concerning the ecological factors that influence sleep patterns. Here, we developed an evolutionary individual-based model to investigate the effect of predation pressure on prey sleep. We investigated three ecological conditions, including one that assumed a dynamic interaction between predator and prey behaviour. In condition 1, we found that monophasic predators (i.e. with one sleep bout per 24h) select for monophasic prey that sleep perfectly out of phase with predators. In condition 2, predators were monophasic but the safety of prey varied as a function of their activity (sleeping versus awake). In this condition, the prey adjusted their sleeping behaviour to lower the risk of predation. Finally, in condition 3, we modelled a more dynamic interaction between predator and prey, with predator activity dependent on prey activity in the previous hour. In this scenario, the prey adjusted their behaviour relative to one another, resulting in either greater or lesser synchrony in prey as a function of predator searching behaviour. Collectively, our model demonstrates that predator behaviour can have a strong influence on prey sleep patterns, including whether prey are monophasic or polyphasic (i.e. with many sleep bouts per 24h). The model further suggests that the timing of sleep relative to predator behaviour may depend strongly on how other potential prey partition the activity period. [ABSTRACT FROM AUTHOR]

Cultural traits spread via multiple mechanisms among individuals within social groups, including via transmission biases that occur when subordinates copy from dominants (prestige transmission), or via common cultural trait variants that are favoured over rare ones (consensus transmission). Most animal populations are subdivided into social groups where cultural learning occurs, yet theoretical studies of cultural trait transmission have tended to focus on within-group transmission dynamics. We developed an agent-based model of cultural transmission in socially structured populations in which a trait arises in one individual and either persists until a stable population equilibrium is reached, or goes extinct. With this model, we systematically varied group size, rates of dispersal among groups, mortality rates, transmission characteristics, the benefit of the cultural trait (including possibly negative benefits), and whether individuals disperse locally or randomly. We used generalized linear models to examine how changes in these parameters influence trait extinction, equilibrium prevalence and time to equilibrium. Four traits increased the probability of extinction: smaller group size, higher background mortality, lower transmission rate and more costly traits (although costly traits sometimes reached an equilibrium). Local dispersal and biased transmission mechanisms (prestige and consensus) had no significant effects on extinction probability, and similar patterns were found for equilibrium prevalence. We found that a lower dispersal rate and local dispersal slowed the time required for a trait to reach equilibrium, as did smaller groups, lower transmission rates and lower costs. Collectively, these analyses reveal that prestige and consensus transmission have weaker effects than other factors associated with demographic and social conditions. [Copyright &y& Elsevier]

Sexually transmitted diseases (STDs) are known to exist in wild and domesticated animals, but little is know about behavioural defences that animals use to reduce the risk of acquiring STDs. Using comparative data and a phylogeny of primates, I investigated whether behaviours hypothesized to reduce STD transmission are correlated with measures of STD risk involving mating promiscuity and life-history traits. Comparative tests revealed no support for genital inspection as a means to identify and avoid infected individuals with genital inspection was performed more commonly by males than females and uncorrelated with mating promiscuity. Primate species characterized by increased promiscuity were not more likely to display genital self-grooming following mating. Similarly, males and females of these species were not more likely to urinate immediately after mating, counter to suggestions that urination flushes microorganisms from the urethra and surrounding genital areas. Finally, monogamy was not correlated with a slow life history, which differs from predictions that monogamy is a response to increased STD risk in long-lived animals. Tests involving monogamy remained unsupported after controlling for potentially confounding variables, and all tests yielded similar results in phylogenetic and nonphylogenetic tests. Few results were significant even before controlling statistically for multiple comparisons, but nonsignificance was unlikely due to low statistical power or poor data quality in all tests. Instead, the comparative patterns were consistent with theoretical models showing that precopulatory behavioural defences to STDs, such as mate choice, are unlikely to be fully effective. In addition, many putative behavioural defences to STDs in primates entail substantial fitness costs in terms of reproductive output, offspring quality and infanticide avoidance. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. [Copyright &y& Elsevier]

Highlights research work on the phylogenetic distribution of exaggerated sexual swellings among primates. Correlation of morphology, physiology and behavior of species with the trait; Confusion of paternity certainty among males; Enabling of females to manipulate male behavior by altering the costs and benefits of mate guarding.

Abstract Humans are thought to exhibit an unusual suite of life history traits relative to other primates, with a longer lifespan, later age at first reproduction, and shorter interbirth interval. These assumptions are key components of popular hypotheses about human life history evolution, but they have yet to be investigated phylogenetically. We applied two phylogenetic comparative methods to investigate whether these human life history traits differ from expectations based on other primates: one fits and selects between Brownian and Ornstein-Uhlenbeck models of trait evolution; the other tests for phylogenetic outliers by predicting phenotypic characteristics based on trait covariation and phylogeny for a species of interest. We found that humans have exceptionally short interbirth intervals, long lifespans, and high birth masses. We failed to find evidence that humans have a delayed age at first reproduction relative to body mass or other covariates. Overall, our results support several previous assertions about the uniqueness of human life history characteristics and the importance of cooperative breeding and socioecology in human life history evolution. However, we suggest that several hypotheses about human life history need to be revised in light of our finding that humans do not have a delayed age at first reproduction. [ABSTRACT FROM AUTHOR]

Conflict resolution is an essential component of primate sociality that has been studied extensively within primate social groups, but few studies have examined how conflict resolution behaviours covary at evolutionary scales. We assembled a standardized data set on social interactions of sexually mature females to analyse patterns of conflict resolution in 15 groups of nine macaque species. Between-group comparisons revealed no significant difference in nonkin reconciliation levels between groups of the same species, whereas substantial interspecific differences were found. We tested for associations between four behavioural traits involving reconciliation and dominance asymmetry that play a central role in primate social systems. Regression analyses using group values indicated that these traits (conciliatory tendencies, proportions of explicit reconciliatory contacts, kin bias and levels of counteraggression) exist as an integrated suite of characters. We found strong phylogenetic signal in most traits, which further indicates that they evolved during the adaptive radiation of macaques. Using the method of independent contrasts, relationships between conciliatory tendencies and proportions of explicit reconciliatory contacts and between kin bias and levels of counteraggression remained consistent after controlling for phylogeny. This reveals that evolutionary change in one trait leads to correlated changes in other traits. Collectively, these results show how comparative studies of detailed behavioural interactions can be used to elucidate primate socioecology. [Copyright &y& Elsevier]

Phylogenetic comparative methods have become standard for investigating evolutionary hypotheses, including in studies of human evolution. While these methods account for the non-independence of trait data due to phylogeny, they often fail to consider intraspecific variation, which may lead to biased or erroneous results. We assessed the degree to which intraspecific variation impacts the results of comparative analyses by investigating the “social brain” hypothesis, which has provided a framework for explaining complex cognition and large brains in humans. This hypothesis suggests that group life imposes a cognitive challenge, with species living in larger social groups having comparably larger neocortex ratios than those living in smaller groups. Primates, however, vary considerably in group size within species, a fact that has been ignored in previous analyses. When within-species variation in group size is high, the common practice of using a mean value to represent the species may be inappropriate. We conducted regression and resampling analyses to ascertain whether the relationship between neocortex ratio and group size across primate species persists after controlling for within-species variation in group size. We found that in a sample of 23 primates, 70% of the variation in group size was due to between-species variation. Controlling for within-species variation in group size did not affect the results of phylogenetic analyses, which continued to show a positive relationship between neocortex ratio and group size. Analyses restricted to non-monogamous primates revealed considerable intraspecific variation in group size, but the positive association between neocortex ratio and group size remained even after controlling for within-species variation in group size. Our findings suggest that the relationship between neocortex size and group size in primates is robust. In addition, our methods and associated computer code provide a way to assess and account for intraspecific variation in other comparative analyses of primate evolution. [ABSTRACT FROM AUTHOR]