Restrictions on roaming Until the past century or so, the movement of wild animals was relatively unrestricted, and their travels contributed substantially to ecological processes. As humans have increasingly altered natural habitats, natural animal movements have been restricted. Tucker et al. examined GPS locations for more than 50 species. In general, animal movements were shorter in areas with high human impact, likely owing to changed behaviors and physical limitations. Besides affecting the species themselves, such changes could have wider effects by limiting the movement of nutrients and altering ecological interactions. Science , this issue p. 466

Understanding how predation risk and plant defenses interactively shape plant distributions is a core challenge in ecology. By combining global positioning system telemetry of an abundant antelope (impala) and its main predators (leopards and wild dogs) with a series of manipulative field experiments, we showed that herbivores' risk-avoidance behavior and plants' antiherbivore defenses interact to determine tree distributions in an African savanna. Well-defended thorny Acacia trees (A. etbaica) were abundant in low-risk areas where impala aggregated but rare in high-risk areas that impala avoided. In contrast, poorly defended trees (A. brevispica) were more abundant in high- than in low-risk areas. Our results suggest that plants can persist in landscapes characterized by intense herbivory, either by defending themselves or by thriving in risky areas where carnivores hunt.

Predation is thought to have been a key selection pressure in primate evolution, especially in the savannah-woodland habitats where several early hominin species lived. However, predator-primate prey relationships are still poorly understood because human presence often deters predators, limiting our ability to quantify the impact of predation. Synchronized high-resolution tracking of leopards (Panthera pardus), vervets (Chlorocebus pygerythrus), and olive baboons (Papio anubis) during a 14-month study in Kenya revealed that increased vulnerability to leopard predation was not associated with higher encounter rates, smaller body size, smaller group size, or greater distance from refuges, contrary to long-standing inferences. Instead, the initiation, rate, timing, and duration of encounters, outcome of approaches, and predation events showed only a diel pattern of differential vulnerability. In the absence of human observers, vervets were more vulnerable during the day, whereas baboons were more vulnerable at night, but overall neither species was more vulnerable than the other. As our results show that leopards avoided baboons during the day and hunted them at night, we suggest that the same pattern would have applied to hominins-because they were even larger than baboons and bipedal, resulting in similarly offensive capability on the ground during the day but poorer agility in the trees at night, especially as they became committed bipeds. Drawing from hominid behavior and archaeopaleontological and ethnographic evidence, we hypothesize that ground-sleeping hominins initially dealt with this formidable threat by using stone tools to modify Acacia branches into 'bomas', thorny enclosures that provided nighttime shelter. The ability of hominins to create their own nightly refuges on the ground wherever Acacia spp. were available would have allowed them to range more widely, a crucial step in furthering the spread of hominins across Africa and beyond.

An understanding of the fundamental causes of the structure of primate communities is important for studies of primate evolutionary history, primate behavioral ecology, and development of conservation strategies. Research into these structuring factors has benefited from new perspectives such as consideration of primate phylogenetic history, metacommunities, and interactions with predators and nonprimate competitors. This review presents the underlying factors of primate community structure within the biogeographic regions of Madagascar, the Neotropics, Africa, and Asia. One of the major differences among these locations likely resulted from the initial primate taxa that colonized each region (a single colonization event in the case of Madagascar and South America, and multiple radiations of higher-level taxa in Africa and Asia). As most primates live in forests, the differences among the forests in these locations, caused by various climatic influences, further influenced speciation and the development of primate communities. Within these habitats, species interactions with different groups of organisms were also instrumental in developing community dynamics. Through an investigation of these fundamental factors, we identify some of the most important effects on primate communities in each region. These findings suggest that low primate richness in Asia may be caused by either the abundance of dipterocarp trees or high levels of monsoon rains. High numbers of frugivores and a lack of folivores in neotropical communities may be associated with competiton with sloths that were already present at the time of initial radiation. Climatic patterns which affect forest structure and productivity in Madagascar may be responsible for high numbers of folivorous lemurs. The identification of these factors are important for the conservation of existing primate communities, and indicate directions for future studies. Yrbk Phys An- A primate community can be loosely defined as all primate species that live together and utilize resources at one geographic location. Each community can also be viewed as the end result of one or more adaptive radiations. That is, ancestral primates have colonized each continent and undergone subsequent species diversification with regard to resource partitioning. As such, comparisons of extant primate communities offer insights into how different evolutionary histories, habitats, and species interactions shaped primate evolution in particular regions. The understanding of how primates migrated, evolved, and currently exist together is also important for planning conservation strategies for their diminishing habitats. Prior studies led researchers to hypotheses about why there are major differences among primate communities on different continents. Our goal is to review the causes associated with these questions and outline possible answers: What are the major causes of differences among primate communities? Why is Asia characterized by low primate species richness? What is the reason for ...