Abstract: n one group each of Plains zebra (six mares, one foal, one subadult) and Asiatic wild asses (seven mares, two foals) at Nuremberg Zoo, food distribution was experimentally changed from clumped (all food in one standard hay rack) to dispersed (one heap per animal). Both groups were characterized by different social structures, which basically remained during the experiment. Plains zebras had an individually structured system of social relationships in a dominance order, wild asses a more egalitarian system without clear-cut rank differences and low frequencies of agonistic interactions. Access to food accordingly was individually (but consistently) different for zebra mares, almost equal for wild ass mares. During the dispersed feeding situation frequencies of agonistic interactions in both species decreased (however non-significantly), individual distances increased but mares also frequently ''visited'' each others' heaps. Feeding time increased for all wild ass mares. Some individuals (in both groups) behaved ''against the trend'' in agonistic behaviour. The results are discussed with regard to food distribution for ungulates in general, and equid social systems.

Abstract: This review focuses on five key evolutionary issues pertaining to animal cognition, defined as the neuronal processes concerned with the acquisition, retention, and use of information. Whereas the use of information, or decision making, has been relatively well examined by students of behavior, evolutionary aspects of other cognitive traits that affect behavior, including perception, learning, memory, and attention, are less well understood. First, there is ample evidence for genetically based individual variation in cognitive traits, although much of the information for some traits comes from humans. Second, several studies documented positive association between cognitive abilities and performance measures linked to fitness. Third, information on the evolution of cognitive traits is available primarily for color vision and decision making. Fourth, much of the data on plasticity of cognitive traits appears to reflect nonadaptive phenotypic plasticity, perhaps because few evolutionary analyses of cognitive plasticity have been carried out. Nonetheless, several studies suggest that cognitive traits show adaptive plasticity, and at least one study documented genetically based individual variation in plasticity. Fifth, whereas assertions that cognition has played a central role in animal evolution are not supported by currently available data, theoretical considerations indicate that cognition may either increase or decrease the rate of evolutionary change.

Abstract: What examples of convergence in higher-level complex cognitive characteristics exist in the animal kingdom? In this paper I will provide evidence that convergent intelligence has occurred in two distantly related mammalian taxa. One of these is the order Cetacea (dolphins, whales and porpoises) and the other is our own order Primates, and in particular the suborder anthropoid primates (monkeys, apes, and humans). Despite a deep evolutionary divergence, adaptation to physically dissimilar environments, and very different neuroanatomical organization, some primates and cetaceans show striking convergence in social behavior, artificial 'language' comprehension, and self-recognition ability. Taken together, these findings have important implications for understanding the generality and specificity of those processes that underlie cognition in different species and the nature of the evolution of intelligence.

Abstract: Mammals show extensive interspecific variation in the form of maternal care. Among ungulates, there is a dichotomy between species in which offspring follow the mother (“following” strategy) versus species in which offspring remain concealed (“hiding” strategy). Here we reveal that the same dichotomy exists among macropods (kangaroos, wallabies and allies). We test three traditional adaptive explanations and one new life history hypothesis, and find very similar patterns among both ungulates and macropods. The three traditional explanations that we tested were that a “following” strategy is associated with (1) open habitat, (2) large mothers, and (3) gregariousness. Our new life-history hypothesis is that a “following strategy” is associated with delayed weaning, and thus with the “slow” end of the slow-fast mammalian life-history continuum, because offspring devote resources to locomotion rather than rapid growth. Our comparative test strongly supports the habitat structure hypothesis and provides some support for this new delayed weaning hypothesis for both ungulates and macropods. We propose that sedentary young in closed habitats benefit energetically by having milk brought to them. In open habitats, predation pressure will select against hiding. Followers will suffer slower growth to independence. Taken together, therefore, our results provide the first quantitative evidence that macropods and ungulates are convergent with respect to interspecific variation in maternal care strategy. In both clades, differences between species in the form of parental care are due to a similar interaction between habitat, social behavior, and life history. Corresponding Editor: B. Crespi

Abstract: Behavioral ecologists have devoted considerable effort to identifying the sources of variation in individual reproductive success. Much of this work has focused on the characteristics of individuals, such as their sex and rank. However, many animals live in stable social groups and the fitness of individuals depends at least in part on the outcome of their interactions with other group members. For example, in many primate species, high dominance rank enhances access to resources and reproductive success. The ability to acquire and maintain high rank often depends on the availability and effectiveness of coalitionary support. Allies may be cultivated and coalitions may be reinforced by affiliative interactions such as grooming, food sharing, and tolerance. These findings suggest that if we want to understand the selective pressures that shape the social behavior of primates, it will be profitable to broaden our focus from the characteristics of individuals to the properties of the relationships that they form with others. The goal of this paper is to discuss a set of methods that can be used to quantify the properties of social relationships.