The Spatial Distribution of Chacma Baboon (Papio ursinus) Habitat Based on an Environmental Envelope Model

Species-specific effects of climate change on the distribution of suitable baboon habitats - Ecological niche modeling of current and Last Glacial Maximum conditions

Baboons (genus Papio) have been proposed as a possible analogous phylogeographic model for intra-African dispersal of hominins during the Pleistocene. Previous studies of the genus reveal complex evolutionary dynamics including introgressive hybridization and, as for hominins, it has been hypothesized that past climate change has been a major driver in their evolutionary history. However, how historical climate changes affected the distribution and extent of baboon habitats is not clear. We therefore employed three ecological niche modeling algorithms (maximum entropy model: MaxEnt; general additive model: GAM; gradient boosting model: GBM) to map suitable habitat of baboons at both genus and species levels under two extreme late-Quaternary climates: current (warm period) and Last Glacial Maximum (LGM, cold period). The three model algorithms predicted habitat suitabilities for the baboon species with high accuracy, as indicated by AUC values of 0.83-0.85 at genus level and ≥0.90 for species. The results suggest that climate change from LGM to current affected the distribution and extent of suitable habitats for the genus Papio only slightly (>80% of the habitat remained suitable). However, and in contrast to our expectation for ecological generalists, individual species have been differentially affected. While P. ursinus and P. anubis lost some of their suitable habitats (net loss 25.5% and 13.3% respectively), P. kindae and P. papio gained large portions (net gain >62%), and P. cynocephalus and P. hamadryas smaller portions (net gain >20%). Overlap among the specific realized climate niches remained small, suggesting only slight overlap of suitable habitat among species. Results of our study further suggest that shifts of suitable habitats could have led to isolation and reconnection of populations which most likely affected gene flow among them. The impact of historic climate changes on baboon habitats might have been similar for other savanna living species, such as hominins.

Ecological niche modeling of the genus Papio

OBJECTIVE

Ecological niche modeling (ENM) has been used to assess how abiotic variables influence species distributions and diversity. Baboons are broadly distributed throughout Africa, yet the degree of climatic specialization is largely unexplored for individual taxa. Also, the influence of climate on baboon phylogenetic divergence is unknown. In this study, we constructed ENMs to investigate how niches vary across Papio species to understand how climatic variables have influenced their biogeography and mode of speciation.

MATERIALS AND METHODS

We used Maxent to generate ENMs by collating locality data for six Papio species and climate information from WorldClim. In addition, we examined the degree of niche overlap among all possible pairs of taxa, which can provide insight into patterns of species diversity. Lastly, we conducted a Mantel test to assess the relationship between niche overlap and estimated time since divergence.

RESULTS

Our models performed moderately to extremely well, with a mean area under the curve value of 0.868. The species with the best models include P. papio and P. kindae, whereas P. hamadryas had the poorest models. We found that most species pairs exhibited significantly different niches. Lastly, we found no significant correlation between niche overlap and divergence times.

DISCUSSION

Niche models had good predictive power, which indicates Papio species distributions are correlated with climatic variables to varying degrees. Significantly little niche overlap and incomplete geographic boundaries suggests these models generally support a parapatric speciation scenario for the genus Papio.

Potential human impact on the environmental central niche of the chacma baboon

Abstract We assessed the human impact on regions identified as the environmental central niche for the chacma baboon(Papio ursinus) across southern Africa. This central niche is the area within an animal’s natural range that is most insulated from changes to the environmental variables that influence that animal’s distribution. We used an environmental envelope model constructed with geographic information system software to predict the geographic extent of the central niche. The predicted chacma baboon central niche was 389 000 km2, with substantial overlap with human settlements in several countries. Of note is that although Botswana contains nearly 60 000 km2 of predicted central niche, the International Union for the Conservation of Nature chacma baboon distribution map implies that much of this area is uninhabited by baboons. A regional assessment of the province of KwaZulu-Natal (South Africa) suggests more than 95% of its central niche is uninhabited. Additionally, the very limited and likely disturbed central niche area in Lesotho coupled with the unknown status of chacma baboons within Lesotho warrants further attention. Overall, it appears likely that significant proportions of the predicted central niche in southern Africa are currently uninhabited by the chacma baboon. These uninhabited areas correspond with areas of high human population density and anthropogenic land alteration. The remaining central niche areas that are still inhabited are potentially key areas for conservation and are important for ensuring the sustainability of future populations. However, these areas may be undergoing degradation whilst also becoming more inaccessible to baboons, thus increasing the difficulty of conservation efforts. This preliminary assessment highlights the urgent need for detailed assessments at a finer scale.

Social effects on foraging behavior and success depend on local environmental conditions

In social groups, individuals' dominance rank, social bonds, and kinship with other group members have been shown to influence their foraging behavior. However, there is growing evidence that the particular effects of these social traits may also depend on local environmental conditions. We investigated this by comparing the foraging behavior of wild chacma baboons, Papio ursinus, under natural conditions and in a field experiment where food was spatially clumped. Data were collected from 55 animals across two troops over a 5-month period, including over 900 agonistic foraging interactions and over 600 food patch visits in each condition. In both conditions, low-ranked individuals received more agonism, but this only translated into reduced foraging performances for low-ranked individuals in the high-competition experimental conditions. Our results suggest one possible reason for this pattern may be low-ranked individuals strategically investing social effort to negotiate foraging tolerance, but the rank-offsetting effect of this investment being overwhelmed in the higher-competition experimental environment. Our results also suggest that individuals may use imbalances in their social bonds to negotiate tolerance from others under a wider range of environmental conditions, but utilize the overall strength of their social bonds in more extreme environments where feeding competition is more intense. These findings highlight that behavioral tactics such as the strategic investment of social effort may allow foragers to mitigate the costs of low rank, but that the effectiveness of these tactics is likely to be limited in certain environments.