Abstract: Predation is a major force in shaping biological communities, both over ecological and evolutionary timescales. In response to predation pressure, prey have evolved characteristics designed to mitigate predation pressure. We evaluated predator foraging biases in relation to prey characteristics across 16 vertebrate communities. We show that although predator biases vary, some prey traits are consistently associated with predator diet composition. Within their acceptable prey size range, predators show positive bias toward larger bodied prey, small-brained prey (controlling for body size), small group size, and terrestriality. Thus, whether predator foraging decisions are passive or active, predator choice exerts differential pressure on prey species according to prey characteristics. Predator biases also were positively associated with early age at maturity, supporting the role of mortality in driving life-history characteristics. These results support several theoretical models of predation including its role as a selective force driving evolutionary changes in life history, brain size and sociality, optimal diet theory, and antiapostatic predation.

Abstract: Abstract  Until recently, few studies have used social network theory (SNT) and metrics to examine how social network structure (SNS) might influence social behavior and social dynamics in non-human animals. Here, we present an overview of why and how the social network approach might be useful for behavioral ecology. We first note four important aspects of SNS that are commonly observed, but relatively rarely quantified: (1) that within a social group, differences among individuals in their social experiences and connections affect individual and group outcomes; (2) that indirect connections can be important (e.g., partners of your partners matter); (3) that individuals differ in their importance in the social network (some can be considered keystone individuals); and (4) that social network traits often carry over across contexts (e.g., SN position in male–male competition can influence later male mating success). We then discuss how these four points, and the social network approach in general, can yield new insights and questions for a broad range of issues in behavioral ecology including: mate choice, alternative mating tactics, male–male competition, cooperation, reciprocal altruism, eavesdropping, kin selection, dominance hierarchies, social learning, information flow, social foraging, and cooperative antipredator behavior. Finally, we suggest future directions including: (1) integrating behavioral syndromes and SNT; (2) comparing space use and SNS; (3) adaptive partner choice and SNS; (4) the dynamics and stability (or instability) of social networks, and (5) group selection shaping SNS.

Abstract: Coalitionary support in agonistic interactions represents cooperation because intervening in a fight is potentially costly to the donor of support but benefits the recipient. Here, we first review the characteristics of, and evolutionary forces favoring, intragroup coalitions in 49 species and find that patterns of intragroup coalition formation are remarkably similar between primates and nonprimates. We then test hypotheses suggesting kin selection, reciprocal altruism, and direct benefits as adaptive explanations for coalitionary interventions among adult female spotted hyenas (Crocuta crocuta) belonging to a large social group in Kenya. As predicted by kin selection theory, females supported close kin most often, and the density (connectedness) of cooperation networks increased with genetic relatedness. Nevertheless, kinship failed to protect females from coalitionary attacks. We found no evidence of enduring alliances based on reciprocal support among unrelated adult females. Instead, donors generally minimized costs to themselves, intervening most often during low-intensity fights and when feeding opportunities were unavailable. Females also gained direct benefits from directing coalitionary attacks toward subordinates. Finally, females monitored the number of dominant bystanders in the “audience” at fights and modified their level of cooperation based on this knowledge. Overall, hyenas made flexible decisions regarding whether or not to intervene in fights, modifying their tendency to cooperate based on multiple types of information about their immediate social and ecological environments. Taken together, these findings indicate that the combined evolutionary forces of kin selection and direct benefits derived from reinforcing the status quo drive coalitionary interventions among adult female spotted hyenas.

Abstract: Considerable interspeci®c variation in female social relationships occurs in gregarious primates, particularly with regard to agonism and cooperation between females and to the quality of female relationships with males. This variation exists alongside variation in female philopatry and dispersal. Socioecological theories have tried to explain variation in female-female social relationships from an evolutionary perspective focused on ecological factors, notably predation and food distribution. According to the current ``ecological model'', predation risk forces females of most diurnal primate species to live in groups; the strength of the contest component of competition for resources within and between groups then largely determines social relationships between females. Social elationships among gregarious females are here characterized as DispersalEgalitarian, Resident-Nepotistic, Resident-Nepotistic-Tolerant, or Resident-Egalitarian. This ecological model has successfully explained i€erences in the occurrence of formal submission signals, decided dominance relation ships, coalitions and female philopatry. Group size and female rank generally a€ect female reproduction success as the model predicts, and studies of closely related species in di€erent ecological circumstances underscore the importance of the model. Some cases, however, can only be explained when we extend the model to incorporate the e€ects of infanticide risk and habitat saturation. We review evidence in support of the ecological model and test the power of alternative models that invoke between-group competition, forced female philopatry, demographic female recruitment, male interventions into female aggression, and male harassment.
Not one of these models can replace the ecological model, which already encompasses the between-group competition. Currently the best model, which explains
several phenomena that the ecological model does not, is a ``socioecological model'' based on the combined importance of ecological factors, habitat saturation and infanticide avoidance. We note some points of similarity and divergence with other mammalian taxa; these remain to be explored in detail.