The physical, behavioral and ecological diversity of baboons (genus Papio) makes them a fruitful source as analogies for understanding early human evolution. This project investigates a widespread but little known species, the kinda baboon (P. kindae), and probes the physiological and genetic bases of its distinctive behaviors and physical features. Besides being unusually small and juvenile in appearance, kinda baboons appear less sexually differentiated than other baboons. Behaving like females of other species, adult male kindas frequently initiate long grooming sessions, while females often give alarm barks, which is normally a male baboon activity. Unexpectedly, kinda baboons hybridize with neighboring chacma baboons (P. ursinus) which are almost twice their size, and are behaviorally more typical. This research project traces the causes of these species differences from the level of observable behavior and anatomy, through the level of development and hormonal control, to the level of the genome. Over 200 kinda, hybrid, and chacma baboons are trapped, sampled, and released unharmed in Kafue National Park, Zambia. Basic biological data such as weight and body measurements are collected along with blood samples. Specialist labs investigate these blood samples for the hormones and other biologically active components that influence growth, sexual differentiation, and behavior, and produce a high-resolution map of the kinda genome. Physiological differences that consistently distinguish kindas can then be tracked to the genetic level, by comparing fast-evolving candidate regions in kindas with homologous regions in other baboon species.

The project is innovative in combining proven, comparatively low-tech field techniques with cutting edge technology in genomics and hormonal physiology. Most immediately, it fills a major gap in our knowledge of a key primate genus. In the long term, it provides insights into behavioral variation and evolution in other species, including humans. In the wider sphere, the project will train graduate students, further scientific collaboration with Zambian Wildlife authorities, and promote the status of baboons in wildlife tourism.

Project Report

Baboons are very wide spread in their distribution, ranging across most of the continent of Africa. While all baboons share some similarities in their appearance, close study shows that there are differences across their range, which results in their being grouped into a number of species. At the edges of each species’ distribution, animals of different species come into contact and interbreeding occurs. Over the four decades that represents our team’s studies of baboons (in Ethiopia, Tanzania and Kenya), we have studied four of the seven (or more) baboon species. However, one species--­the Kinda baboon-- had been observed, but not properly studied, and this formed the basis of our proposed collaboration. We had several goals for this project. The first, and most important, was to gather information on this hitherto little studied species of baboon that inhabits Zambia, Angola, the Congo and westernmost Tanzania. We had conducted a number of on-the-ground surveys between 1999 and 2007 which revealed that this smallest baboon species has a range which overlaps two other baboon species in Zambia (the very large, grayfooted chacma and the well-known yellow baboon): that it interbreeds with both species where their ranges meet; and that its infants typically have white fur at birth, rather than the dark colored fur typical of all other baboon species. While they look similar to yellow baboons, they have a number of distinctive features: the fur on the top of their heads typically forms a midline crest, they have pink skin around the eyes, which makes them appear as if they were wearing spectacles, they have short faces and the size difference between males and females is far less than in other baboon species. We also noted unusual behaviors in Kindas that clearly distinguished them from other baboons. In most baboon species males show greatest interest in females when they are receptive to mating. At such times, males show their interest by grooming females; at times other than this, males groom females little. Kinda baboon males, on the other hand, seemed to engage in long, intensive grooming interactions with females , no matter whether they are sexually receptive or not. These findings suggested a number of questions: Are Kindas different from other baboons in hormones that are related to behavior? Are their hormones that are related to growth distinctive in some way to produce their small appearance and reduced difference between the sexes? Are they distinctive genetically from other baboons? And when they contact other baboon species, with their own unique behavioral programs, what are the behavioral and physical features that influence whether and how interbreeding occurs? Such questions­ about similarities and differences between species, and the kind of interactions that occur when they meet ­have become of great interest, given the recent understanding of interbreeding that occurred between Neanderthals and modern humans in the not very distant past. To address these questions we planned two years of capture and biological sampling of the baboons of Kafue National Park in western Zambia. We were given permission to do this research by the Zambian Wildlife authority, and were joined by ZAWA staff and a veterinarian from the Department of Veterinary and Livestock Development in Lusaka, Zambia. Fieldwork involved collecting blood for genetic/genomic and hormonal studies, feces for genetic and hormone studies and for studies of the baboon microbiome, and bodily measurements and impressions of their teeth. At Chunga, in the northern part of the park, only kinda baboons are found; at Ngoma 215 kilometers to the south, our previous surveys had shown a hybrid zone between the small kindas and the very large greyfooted chacmas. In 2011 we captured 76 kinda baboons at Chunga; in 2012 we captured 16 kinda-grayfoot hybrids at Ngoma. We extended our sample for genetic studies from Ngoma by supporting a doctoral study on behavior and genetics (from fecal samples) in the hybrid zone. While some analyses continue, we have found that the small size of kindas is reflected in their growth hormones, and that Kinda males have high levels of the hormone prolactin, which may be related to their grooming behavior, and possibly to their paternity. Surprisingly, they have high levels of testosterone and large testicles for their body size. Taken together, these features may explain our findings that Kinda males outcompete grayfoot males when the two species intermingle. Despite being half the size, Kinda males’ reproductive physiology allows them to successfully compete with grayfoot males, while their affiliative behavior makes them attractive to grayfoot females. Thus, as anticipated, both behavior and biology are influencing interbreeding at the hybrid zone. We anticipate that genome sequencing studies underway will help to illuminate the genetic bases for these complex traits.

National Science Foundation (NSF)
Division of Behavioral and Cognitive Sciences (BCS)
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Rebecca Ferrell
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Washington University
Saint Louis
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