Influence of rainfall on sleeping site choice by a group of anubis baboons (Papio anubis).

For diurnal nonhuman primates, shifting among different sleeping sites may provide multiple benefits such as better protection from predators, reduced risk of parasitic infection, and closer proximity to spatially and temporally heterogeneous food and water. This last benefit may be particularly important in sleeping site selection by primates living in savanna-woodlands where rainfall is more limited and more seasonally pronounced than in rainforests. Here, we examined the influence of rainfall, a factor that affects food and water availability, on the use of sleeping sites by anubis baboons (Papio anubis) over two 13-month study periods that differed in rainfall patterns. We predicted that during wet periods, when food and water availability should be higher, the study group would limit the number of sleeping sites and would stay at each one for more consecutive nights than during dry periods. Conversely, we predicted that during dry periods the group would increase the number of sleeping sites and stay at each one for fewer consecutive nights as they searched more widely for food and water. We also predicted that the group would more often choose sleeping sites closer to the center of the area used during daytime (between 07:00 and 19:00) during wet months than during dry months. Using Global Positioning System data from collared individuals, we found that our first prediction was not supported on either monthly or yearly timescales, although past monthly rainfall predicted the use of the main sleeping site in the second study period. Our second prediction was supported only on a yearly timescale. This study suggests that baboons' choice of sleeping sites is fluid over time while being sensitive to local environmental conditions, one of which may be rainfall.

Effects of body size on estimation of mammalian area requirements.

Accurately quantifying species' area requirements is a prerequisite for effective area-based conservation. This typically involves collecting tracking data on species of interest and then conducting home-range analyses. Problematically, autocorrelation in tracking data can result in space needs being severely underestimated. Based on the previous work, we hypothesized the magnitude of underestimation varies with body mass, a relationship that could have serious conservation implications. To evaluate this hypothesis for terrestrial mammals, we estimated home-range areas with global positioning system (GPS) locations from 757 individuals across 61 globally distributed mammalian species with body masses ranging from 0.4 to 4000 kg. We then applied block cross-validation to quantify bias in empirical home-range estimates. Area requirements of mammals <10 kg were underestimated by a mean approximately15%, and species weighing approximately100 kg were underestimated by approximately50% on average. Thus, we found area estimation was subject to autocorrelation-induced bias that was worse for large species. Combined with the fact that extinction risk increases as body mass increases, the allometric scaling of bias we observed suggests the most threatened species are also likely to be those with the least accurate home-range estimates. As a correction, we tested whether data thinning or autocorrelation-informed home-range estimation minimized the scaling effect of autocorrelation on area estimates. Data thinning required an approximately93% data loss to achieve statistical independence with 95% confidence and was, therefore, not a viable solution. In contrast, autocorrelation-informed home-range estimation resulted in consistently accurate estimates irrespective of mass. When relating body mass to home range size, we detected that correcting for autocorrelation resulted in a scaling exponent significantly >1, meaning the scaling of the relationship changed substantially at the upper end of the mass spectrum.

Efectos del Tamaño Corporal sobre la Estimación de los Requerimientos de Área de Mamíferos Resumen La cuantificación precisa de los requerimientos de área de una especie es un prerrequisito para que la conservación basada en áreas sea efectiva. Esto comúnmente implica la recolección de datos de rastreo de la especie de interés para después realizar análisis de la distribución local. De manera problemática, la autocorrelación en los datos de rastreo puede resultar en una subestimación grave de las necesidades de espacio. Con base en trabajos previos, formulamos una hipótesis en la que supusimos que la magnitud de la subestimación varía con la masa corporal, una relación que podría tener implicaciones serias para la conservación. Para probar esta hipótesis en mamíferos terrestres, estimamos las áreas de distribución local con las ubicaciones en GPS de 757 individuos de 61 especies de mamíferos distribuidas mundialmente con una masa corporal entre 0.4 y 4,000 kg. Después aplicamos una validación cruzada en bloque para cuantificar el sesgo en estimaciones empíricas de la distribución local. Los requerimientos de área de los mamíferos <10 kg fueron subestimados por una media ∼15% y las especies con una masa ∼100 kg fueron subestimadas en ∼50% en promedio. Por lo tanto, encontramos que la estimación del área estaba sujeta al sesgo inducido por la autocorrelación, el cual era peor para las especies de talla grande. En combinación con el hecho de que el riesgo de extinción incrementa conforme aumenta la masa corporal, el escalamiento alométrico del sesgo que observamos sugiere que la mayoría de las especies amenazadas también tienen la probabilidad de ser aquellas especies con las estimaciones de distribución local menos acertadas. Como corrección, probamos si la reducción de datos o la estimación de la distribución local informada por la autocorrelación minimizan el efecto de escalamiento que tiene la autocorrelación sobre las estimaciones de área. La reducción de datos requirió una pérdida de datos del ∼93% para lograr la independencia estadística con un 95% de confianza y por lo tanto no fue una solución viable. Al contrario, la estimación de la distribución local informada por la autocorrelación resultó en estimaciones constantemente precisas sin importar la masa corporal. Cuando relacionamos la masa corporal con el tamaño de la distribución local, detectamos que la corrección de la autocorrelación resultó en un exponente de escalamiento significativamente >1, lo que significa que el escalamiento de la relación cambió sustancialmente en el extremo superior del espectro de la masa corporal.

Capture, immobilization, and Global Positioning System collaring of olive baboons (Papio anubis) and vervets (Chlorocebus pygerythrus): Lessons learned and suggested best practices.

As the value of Global Positioning System (GPS) technology in addressing primatological questions becomes more obvious, more studies will include capturing and collaring primates, with concomitant increased risk of adverse consequences to primate subjects. Here we detail our experiences in capturing, immobilizing, and placing GPS collars on six olive baboons (Papio anubis) in four groups and 12 vervet monkeys (Chlorocebus pygerythrus) in five groups in Kenya. We captured baboons with cage traps and vervets with box traps, immobilized them, and attached GPS collars that were to be worn for 1 year. Adverse consequences from the trapping effort included incidental death of two nonsubjects (an adult female and her dependent infant), temporary rectal prolapse in one baboon, superficial wounds on the crown of the head in two vervets, and failure to recapture/remove collars from two baboons and two vervets. Obvious negative effects from wearing collars were limited to abrasions around the neck of one vervet. A possible, and if so, serious, adverse effect was greater mortality for collared adult female vervets compared with known uncollared adult female vervets, largely due to leopard (Panthera pardus) predation. Collared animals could be more vulnerable to predation because trapping favors bolder individuals, who may also be more vulnerable to predation, or because collars could slow them down or make them more noticeable to predators. Along with recommendations made by others, we suggest that future studies diversify trapping bait to minimize the risk of rectal prolapse, avoid capturing the first individuals to enter traps, test the movement speeds of collared versus noncollared animals, include a release system on the collars to avoid retrapping failure, and publish both positive and negative effects of capturing, immobilizing, and collaring.

Complete rectal prolapse in wild anubis baboons (Papio anubis).

This report describes two cases of rectal prolapse in wild anubis baboons (Papio anubis), with one spontaneous resolution. Both occurred after individuals consumed low-water, high-fibre dried maize during provisioning prior to capture, while one also experienced distress during capture.

The role of sleeping sites in the predator-prey dynamics of leopards and olive baboons.

Predation is widely recognized as an important selective pressure on prey animals such as baboons (Papio spp.), which face high leopard (Panthera pardus) predation risk, particularly at night. Baboons regularly sleep on cliff faces and in trees at night, ostensibly to avoid such predators. Despite retreating to such "refuges," baboons are most often killed by leopards at or near their sleeping sites. Because of the challenges of studying nocturnal behavior and human-averse predators, few systematic data exist to reveal how leopard ranging near baboon sleeping sites influences baboons' selection of sites and behavior at those sites. To investigate leopard-baboon dynamics at sleeping sites we deployed GPS/VHF radio collars on six representatives of four baboon groups and four leopards during a 14-month field study in Kenya. We used locations recorded every 15 min to identify baboons' cliffside and riverine sleeping sites, the frequency and duration of leopard visits to these sites, and baboons' adjustments in site use after leopard visits. Collared leopards visited riverine sites more frequently than cliffside sites, whereas most baboon groups strongly preferred cliffside sites, suggesting that leopard visits were often due to factors other than baboon presence, and that baboons used cliffside sites to reduce their risk of leopard predation. Regardless of type, collared leopards remained near baboon-occupied sleeping sites longer than vacant ones, indicating interest in hunting baboons then. Baboons at riverine sites departed later on mornings after leopard visits. Baboon groups occasionally shared sleeping sites simultaneously, possibly reducing risk through dilution. However, they did not reduce risk by frequently changing sleeping sites, minimizing detection at sleeping sites, or after leopard visits, arriving earlier the next evening or moving to a different site. Future research should explore if baboons readily detect nocturnal leopard presence and if predation-related changes in sleeping site use have cascading ecological effects.

GPS-identified vulnerabilities of savannah-woodland primates to leopard predation and their implications for early hominins.

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.

GPS-identified, low-level nocturnal activity of vervets (Chlorocebus pygerythrus) and olive baboons (Papio anubis) in Laikipia, Kenya.

OBJECTIVES: Except for owl monkeys (Aotus spp.), all anthropoid primates are considered strictly diurnal. Recent studies leveraging new technologies have shown, however, that some diurnal anthropoids also engage in nocturnal activity. Here we examine the extent to which vervets (Chlorocebus pygerythrus) and olive baboons (Papio anubis) are active at night. MATERIALS AND METHODS: We deployed GPS collars with tri-axial accelerometer data loggers on 18 free-ranging adult females: 12 vervets spread among 5 social groups, and 6 olive baboons spread among 4 groups. Their locations were recorded every 15 min, and their activity levels, for 3 s/min over 7.5 months. We also used camera traps that were triggered by heat and movement at seven sleeping sites. RESULTS: Travel was detected on 0.4% of 2,029 vervet-nights involving 3 vervets and 1.1% of 1,109 baboon-nights involving 5 baboons. Travel was mainly arboreal for vervets but mainly terrestrial for baboons. During the night, vervets and baboons were active 13% and 15% of the time, respectively. Activity varied little throughout the night and appeared unaffected by moon phase. DISCUSSION: Our results confirm the low nocturnality of vervets and olive baboons, which we suggest is related to living near the equator with consistent 12-hr days, in contrast to other anthropoids that are more active at night. Since anthropoid primates are thought to have evolved in northern latitudes, with later dispersal to tropical latitudes, our results may have implications for understanding the evolution of anthropoid diurnality.

Primate communities: past, present, and possible future.

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 competition 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.