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We present data on the spread of terrestrial activities in one group of wild northern muriqui monkeys (Brachyteles hypoxanthus). Both males and females consumed fruit, drank, rested, traveled, and socialized terrestrially, but proportionately more males spent significantly more of their time on the ground than females, and females were more likely to engage in terrestrial activities when accompanied by males than when by themselves. Terrestrial activities occurred in both open and closed habitats where arboreal substrates were available and utilized by other individuals engaged in similar activities. Ecological and demographic factors may have stimulated the muriquis' vertical niche expansion, but increases in the frequency and diversity of terrestrial activities, the high proportion of group members that engage in terrestriality, and its diffusion along male-biased social bonds are consistent with the development of a local terrestrial tradition similar to other types of traditions described in other primates. [Key words: terrestriality, ecology, predation, tradition]

The evolution of primate behavioral density can be seen from different levels of analyses such as the individual behavior patterns and the effects of individual behavior on the demography and genetics of local populations. Multilevel studies provide insights into the range of behavioral variations.

Frameworks in research and knowledge integration on fission-fusion dynamics are proposed. Social systems could be described in terms of the extent to which they express fission-fusion dynamics.

The 957-ha forest at the Estacao Biologica de Caratinga/Reserva Particular do Patrimonio Natural-Feliciano Miguel Abdala, in Minas Gerais, Brazil, supports one of the largest known populations of the critically endangered northern muriqui (Brachyteles hypoxanthus). We combine long-term data on one group that has been monitored since 1982 with new data obtained on the other three groups since 2002 and 2003 to describe the demographic structure of this population, evaluate its potential for future growth, and predict how dispersal and competitive regimes may change in response to current demographic conditions. As of January 2005, the 226 individuals in the population were divided into four mixed-sex groups with 37-77 members, and an all-male unit whose eight males maintained transient associations with two of the mixed-sex groups. Although 51.77% of the population was female, the sex ratio among adults and subadults was female-biased (0.75), while that among immatures was male-biased (1.47). Consistent with expectations from mean interbirth intervals, 64.18% of adult females gave birth in 2003 and 2004. However, by January 2005, only 52.31% of adult females were still carrying infants KEY WORDS northern muriqui; Brachyteles hypoxanthus; demography; infant mortality; sex ratios

Fecal androgen and estradiol levels in female northern muriquis were measured at the Estacao Biologica de Caratinga/RPPN Feliciano Miguel Abdala, Minas Gerais, Brazil, to evaluate the hormonal bases underlying individual variation in the resumption of cycling and conception. It was found that androgen levels were significantly lower in females than in males, and that there were no consistent patterns in female androgen levels across precycling or cycling conditions.

Advances in field-based studies of primate behavioral endocrinology are presented, which shows that widespread application of noninvasive methods for measuring steroid levels in wild primates has revolutionized primate field studies in little more than a decade. This has made it possible for field workers to investigate questions about hormone-behavior relationships in ways that were previously feasible only in captive settings by noninvasive methods for obtaining primate endocrinological data.

The growth of primate field studies has occurred along multiple dimensions representing expansion in the number of species studied, comparative studies of different populations of the same species, and populations and groups studied over time. The accumulation of data on a broader taxonomic diversity of primates has contributed to advances in the use of comparative methods for gaining insights into interspecific variation in behavior patterns, but the incorporation of intraspecific variation into comparative models of behavior has lagged behind. This delay can be attributed, in part, to the slow rate at which the interacting effects of life history and demography on behavior emerge in slow-growing, long-lived primates. It may also reflect the anthropocentric foundation of field primatology, which historically focused on interspecific comparisons with humans instead of interpopulation variation among primates. Conservation concerns have stimulated new thinking about the importance of populations and the range of behavioral variation that populations maintain. The integration of intra- and interspecific behavioral variation will distinguish the next generation of comparative models in primatology, and set a new agenda as field primatology comes of age. KEY WORDS primate field studies; intraspecific variation; life history; demography; populations

Nonhuman primates occupy a special niche in anthropology because of the comparative insights into humans they provide. Initial anthropological interest in primates targeted the apes for their close phylogenetic relationships with humans, and the semiterrestrial Old World monkeys for their ecological similarities with hominids adapting to life on the ground. From the earliest anecdotal reports of tool use and hunting to more contemporary quantitative analyses of local 'cultural' traditions, nonhuman primates have challenged deep-rooted concepts of human uniqueness and redefined the boundaries between us and other animals. Yet, despite the long-standing influence of primate studies in anthropology, approaches to studying primates began diverging from those of earlier ethnographers. Advances in primatology, particularly during the 1990s, have included a much deeper understanding of how ecology, phylogeny, and demography affect behavior. Insights into intraspecific, population-level variation represent an important area of convergence between primatology, other areas of anthropology, and conservation biology. [Keywords: primate behavioral ecology, anthropocentrism, evolutionary theory, systematic methods, biology]

Reflections on physical anthropology are offered, with a focus on primate behavioral ecology. Topics include advances in the understanding of behavioral diversity and challenges for the future.

Anthropological interest in nonhuman primates as models for human behavioral evolution has tended to focus on a relatively small number of species. This emphasis, coupled with a search for unifying principles that explain behavior, has led to a widespread perception of the semi-terrestrial cercopithecines as 'typical,' and therefore characteristic of most other primates. The prevalence of male-biased dispersal and female philo-patry, the use of aggression to establish and maintain hierarchical relationships, and the occurrence of sex for exclusively reproductive purposes have been challenged repeatedly, but the cercopithecine model of primate behavior has nonetheless persisted in much of the anthropological literature. This review incorporates accumulating data on a diversity of primates to examine the myth of the typical primate. The roles of kinship, aggression, and sex in mediating primate social relationships are far less uniform across primates than the myth has implied, raising questions about the generality of models of primate social systems derived from 'typical' primates. Acknowledging existing diversity and encompassing it in more accurate portrayals of primate behavioral ecology requires consideration of the interacting effects of phylogenetic, demographic, ontogenetic, and physiological variables. KEY WORDS Cercopithecines, 'Typical' primates, Kinship, Dispersal, Aggression, Dominance, Sex, Reproduction

A study of ten mothers, each with two-six offsprings from August 2003- May 2004 at the RPPN- Feliciano Miguel Abdala in Minas Gerais, Brazil, to determine the mother-offspring relationship in wild northern muriquis (Brachyteles hypoxanthus), where males are philopatric, females generally disperse before puberty, and social relationships between and among males and females are egalitarian is mentioned. The observation of non-preferential relation between muriqui mother and their older male offspring indicate that extended maternal investment in offspring is of nominal importance in their egalitarian community in comparison with its significance for species inhibiting in hierarchical societies.

The article reports the observations made in Brazil, on two groups of northern muriquis which are basically arboreal in nature. The different types of ground use by the two groups are examined and the factors responsible for this are explained.

Hormonal and behavioral changes in wild male and female northern muriquis (Brachyteles arachnoides hypoxanthus) during six-month period of onset of mating and conception seasons in Brazil are investigated. Females experienced two to seven cycles prior to conceiving after the onset of the groups mating season, while male cortisol levels were positively correlated between years.