Animals are faced with a potentially over-whelming number of factors when foraging for food resources that differ in size, quality (energy available, rare nutrients, ease of digestion), distance, ease of access, predation risk, inducement of competition, etc. How they make quick decisions regarding which resources to visit is largely unknown. In our lab, we are utilizing foraging experiments to understand how vervets find food, solve multi-destination routes with several resources, and decide what resources to visit first. In our study system at Nabugabo, Uganda, individual vervets voluntarily leave their group to complete our experiments before returning and going through the experiment with others. This has allowed us to compare the same individuals for decisions made while solitary versus when social, showing different strategies in these situations based on dominance rank. We are collaborating with Dr. Chris Beck at the Toronto Intelligent Decision Engineering Laboratory at the University of Toronto (https://tidel.mie.utoronto.ca/beck.php) to design foraging arrays with optimization software and determine exactly how vervets make foraging decisions.
Leadership and Movement Ecology in Vervet Monkeys
Animal movement research has blossomed in the last decade, benefiting from better methodologies and technologies. We are applying these new methods to better understand how vervet groups move through their home range and search for food resources. We are also examining who leads group progressions, how individuals garner support, and how success in leadership can change over the life history of an animal.
Understanding the Social Structure of Rwenzori Angolan Colobus
We have determined that Colobus angolensis ruwenzorii at Nabugabo, Uganda are forming a multi-level society that is unique among primates in that about half the core units are uni-male/multi-female (OMUs) and half are multi-male/multi-female (MMUs). There are at least three tiers of social organization with core units clustering into clans that share a range in a band tier. These MMUs have several reproductive males that are socially integrated and that show bonding behaviours with one another. Our goals are to understand patterns of sex-biased dispersal in this species and determine the form of male relationships to understand how tolerant male relationships evolved. To do this, we are doing genetic analyses in collaboration with Dr. Eva Wikberg at the University of Texas San Antonio (https://evawikberg.com/). We are also working to understand the costs and benefits to females of living in different unit types. We are collaborating with Dr. Rudy Boonstra at the University of Toronto Scarborough (https://www.utsc.utoronto.ca/~boonstra/) to investigate the underlying hormonal patterns in maternal strategies and male bonding. This work will allow a greater understanding the larger impacts of ecological constraints and the strategies of group mates on the evolution of primate social systems.
Male-Infant Interactions in Rwenzori Angolan Colobus
C. a. ruwnenzorii show male natal attraction and infant handling at far higher rates than those seen in congeners. All males in core units handle infants and pass infants from male to male. We are working on understanding why these interactions are so common and how they evolved.
Photo credit: Sam Stead
Male and Female Strategies Driving Social Organization in Ursine Colobus
During my MA at the University of Calgary under the supervision of Dr. James D. Paterson and my PhD with Dr. Pascale Sicotte (https://antharky.ucalgary.ca/sicotte/) I worked at the Boabeng-Fiema Monkey Sanctuary in Ghana where I studied social organization in ursine (or white-thighed) colobus (Colobus vellerosus). I contrasted ecological factors (i.e., range size, food availability, scramble competition for food) with social factors (i.e., infanticide risk, male sexual coercion, male advertisement, female mate choice) to explain variation in group size and group composition. I found that the rate of infanticide by immigrant males was high and that resident males often defended infants. While food competition constrained group size at the upper end of the continuum, infanticide risk played a more important role in determining social organization, limiting group size earlier and having more of an effect on group composition. Infanticide risk increased with female group size because immigrant males were attracted to larger female groups, thus females attempted to keep group size small by resisting female immigration, evicting maturing nulliparous females, and dispersing when groups became at risk for male takeover. Male quality was found to be important to decreasing the risk of infanticide and females attempted to immigrate into groups where the male(s) won more encounters against the male(s) in the females’ own group. Within groups, male agonistic display output indicated fighting ability; however, males did not vary in their testosterone or parasite levels except when they dropped in rank and were involved in male-male fights. Females did not appear to use male agonistic display to inform their mate choices and seemed to mate promiscuously, perhaps as a counter-strategy to the high rates of infanticide.