Aggressive behavior and dominance hierarchies in female sable antelope,Hippotragus niger: Implications for captive management

Social interactions of adult female sable antelope, Hippotragus niger, were observed at the National Zoological Park's Conservation and Research Center. Aggressive behavior was quantified for two herds containing 8 and 11 females. Aggression was lowest at calving, and highest near the time of conception. Dominance hierarchies were strictly linear and stable over time. Dominance rank was highly correlated with age, with the oldest females achieving highest rank. High-ranking females initiated more aggression and were more likely to behave aggressively towards a newly introduced adult female. The newly introduced individual was the victim of prolonged, intense group chases and was permanently excluded from the herd. Low-ranking females directed more aggression at yearling herd members than did high-ranking females. Temporary absences by herd members resulted in long-lasting, substantial increases in received aggression upon their return. Because of their aggressive nature, sable antelope present a challenge to captive management. © 1993 Wiley-Liss, Inc.     

Is sexual segregation in the guppy, <Emphasis Type="Italic">Poecilia reticulata</Emphasis>, consistentwith the predation risk hypothesis?

We examined the importance of sex differences in predation risk in generating sexual segregation in the guppy, Poecilia reticulata. We hypothesised that sex differences in predation risk will result in habitat segregation and ultimately social segregation of the sexes, with the more vulnerable sex (males in this case) using safer habitats. In accordance with the predation risk hypothesis we observed sexual segregation in a population associated with high but not low predation risk. Under high predation risk we observed a larger proportion of males in shallow marginal habitats resulting in habitat segregation and ultimately social segregation of the sexes. Furthermore, habitat segregation by sex was associated with habitat segregation by body length with shoals in deeper water having a larger mean body length. Shoaling fish species have been key models in investigating group living, and further research directed towards understanding sexual segregation in other fish species would be valuable.     

Primate group size and interpreting socioecological models: Do folivores really play by different rules?

Because primates display such remarkable diversity, they are an ideal taxon within which to examine the evolutionary significance of group living and the ecological factors responsible for variation in social organization. However, as with any social vertebrate, the ecological determinants of primate social variability are not easily identified. Interspecific variation in group size and social organization results from the compromises required to accommodate the associative and dissociative forces of many factors, including predation, 1 - 3 conspecific harassment and infanticide, 4 - 6 foraging competition 1 , 7 and cooperation, 8 dominance interactions, 9 reproductive strategies, and socialization. 10 - 12 Causative explanations have emerged primarily through the construction of theoretical models that organize the observed variation in primate social organization and group size relative to measurable ecological variation.     

Proboscis monkey (Nasalis larvatus) social organization: Nature and possible functions of intergroup patterns of association

Proboscis monkey (Nasalis larvatus) socioecology was studied at the Natai Lengkuas Station, Tanjung Puting National Park, in Kalimantan Tengah, Indonesia. Data on the nature of intergroup interactions were collected on ten one-male groups and two all-male groups using event sampling during follows and also through evening census surveys. Proboscis monkeys form stable one-male groups, with specific groups regularly associating at their sleeping sites (band members). Both intraband and interband high-intensity agonistic displays (slapping, chasing, biting) were rare. Lower intensity agonistic displays (vocalizations, leaping-branch shaking, and erect penis and open-mouth displays) occurred frequently. Temporal avoidance between bands may have been mediated by early morning vocalizations and branch shaking displays by the adult males. Associations between groups may play a role in displacement avoidance and/or predation avoidance.     

Predicting the Competitive Regime of Female <Emphasis Type="Italic">Colobus vellerosus</Emphasis> from the Distribution of Food Resources

We examined the spatial and temporal distribution of the foods of ursine colobus (Colobus vellerosus) at Boabeng-Fiema, Ghana as a means to predict the monopolizablity and usurpability of their food resources. Recent evidence suggests that food may not be limiting for folivorous primates, and that male sexual coercion may be a more important influence on folivore social organization. To address the question, we collected focal data on the feeding behavior of adult females and males over 11 mo (September 2000-August 2001) on 2 groups: WW (n = 31–33 individuals) and B (n = 8–16 individuals). We also conducted phenological monitoring and a tree survey of the two-group home ranges to establish food availability and distribution. We used 2 behavioral or organism-defined indicators of feeding behavior to assess potential resource contestability: food site residence time and distance moved between food sites. The colobus fed on a high diversity of species, most of their food trees were not clumped in distribution, within-tree interfood distances were short, and food trees were large. The only condition associated with the potential for monopolization was low food tree density. However, low food tree density may be offset by the colobus’ use of large trees. Taken together, the ecological and behavioral indicators suggest the food resources of Colobus vellerosus had a low potential for monopolization. Our results also indicate mature leaves had the longest food site residence time, which may suggest they should be the most usurpable plant part, though their presumed low quality and high abundance probably counteracted the effect. The pattern implied the potential for direct feeding competition among Colobus vellerosus at Boabeng-Fiema was low and agonistic interactions over food are not expected. Instead, a group size effect on feeding efficiency should be a more predominant influence on feeding efficiency, if food is limiting for the species.     

Fear of feces? Tradeoffs between disease risk and foraging drive animal activity around raccoon latrines

Fear of predation alters prey behavior, which can indirectly alter entire landscapes. A parasite‐induced ecology of fear might also exist if animals avoid parasite‐contaminated resources when infection costs outweigh foraging benefits. To investigate whether animals avoid parasite contaminated sites, and if such avoidance balances disease costs and foraging gains, we monitored animal behavior at raccoon latrines – sites that concentrate both seeds and pathogenic parasite eggs. Using wildlife cameras, we documented over 40 potentially susceptible vertebrate species in latrines and adjacent habitat. Latrine contact rates reflected background activity, diet preferences and disease risk. Disease‐tolerant raccoons and rats displayed significant site attraction, while susceptible birds and small mammals avoided these high‐risk sites. This suggests that parasites, like predators, might create a landscape of fear for vulnerable hosts. Such non‐consumptive parasite effects could alter disease transmission, population dynamics, and even ecosystem structure.     

Seasonal selection of soil types and grass swards by roan antelope in a South African savanna

Roan antelope are distributed mainly in regions characterized by infertile soils, offering food of low quality. We hypothesized that roan may select localities with higher soil nutrient levels and/or grass swards with more favourable properties in terms of food abundance or quality than generally available in those regions. Roan antelope were observed in a savanna region in South Africa where soils of widely varying nutrient status occurred. Roan favoured open grassland over wooded savanna areas. During the wet season, roan preferred sites with felsite‐derived soil of intermediate soil nutrient status. Grasslands growing on nutrient enriched alluvial soils were preferred outside of the early wet season, although most of the favourable sward characteristics were present in other landscape units. Food quantity, rather than quality appeared to attract roan to foraging sites in the late wet and early dry seasons. Food quality appeared more important in the early wet and late dry seasons. The higher degree of clustering of leafy material within foraging swards seemed to be an additional discriminating factor. The factors governing the selection of foraging sites by roan did not seem notably different from those influencing other species of grazing ruminant, but roan nevertheless seemed tolerant of stemmy grasslands growing on nutrient richer substrates.     

Managing the social environments of flamingos for reproductive success

Recent research has shown that large flamingo flocks are more likely to experience reproductive success than small flocks and that there is a positive relationship between behavioral stimulation from group displays and reproductive success. This study compares the group displays and reproductive success in a captive flock of Caribbean flamingos over 6 years at the National Zoological Park. Birds were added to the flock in two different years. In each case, the flock produced fertile eggs during the breeding season following the addition of new birds. Furthermore, the addition of new birds in 1988, and then again in 1991, significantly increased group display activity over the previous year when the flock size was lower. That the addition of birds stimulated group display activity suggests an alternative management strategy for promoting reproduction in captivity: separate birds in a flock and then reunite them prior to the breeding season. © 1994 Wiley-Liss, Inc.