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Douglas Kamaru - Linkages Between Mutualism Breakdowns, Landscape Change, and Predator-Prey Dynamics in a Human-Occupied Savanna

The BI enhancement award is timely and very significant in supporting my work. Results from my project will illuminate the cascading effects of invasion of big-headed ants on predator-prey interactions and how interactions between lions and their prey will translate to changes in the abundance of each. In so doing, my work will yield predictions for wildlife populations—in particular lions, which are listed as “Vulnerable” by the IUCN—in post-invasion landscapes. I will work with community schools adjacent to the Ol Pejeta Conservancy (my study site) through a conservation mentorship program, by engaging young students in deployment and servicing of camera traps, image classification, and lion tracking, thus providing opportunity to interact directly with wildlife and wildlife conservationists. Finally, I will advise students at local universities through internship placements and attachments in order to enhance their knowledge and skills in scientific research.

Douglas Kamaru

Biodiversity Graduate Student Research Enhancement Grant Awardee 

Department of Zoology & Physiology
Graduate Advisor: Dr. Jacob R. Goheen

Project Summary:

The big-headed ant (Pheidole megacephala) is one of the world’s “worst invasive species”, posing significant threats to agriculture and biodiversity across all seven biogeographic realms. Over the past two decades, invasion of the big-headed ant has disrupted a foundational mutualism between the monodominant whistling-thorn tree (Acacia drepanolobium) and their symbiotic bodyguards, native ants in the genus Crematogaster. In exchange for food and shelter, Crematogaster ants protect trees from catastrophic herbivory by elephants (Loxodonta africana). Because big-headed ants kill and displace these native mutualists, trees are rendered defenseless against elephants, such that elephants in post-invasion landscapes transform bushland savannas into open grasslands by browsing, breaking, and uprooting adult trees.

By concealing predators and providing cover for ambushes, trees shape the outcome of predator-prey dynamics in African savannas: in particular, lions (Panthera leo) are more successful at killing prey where tree cover is high at my study site in central Kenya and elsewhere in sub-Saharan Africa. Consequently, wild ungulates like antelopes and plains zebra (Equus burchelli) congregate more in open areas where tree cover is relatively low, because such areas are perceived to be safer. I will test the hypothesis that disruption of the ant-tree mutualism cascades to influence interactions between lions and their prey. Specifically, I will quantify (1) whether and how habitat selection by wild ungulates is altered by big-headed ant invasion; and (2) whether and how the outcome of hunting forays by lions is in turn affected by big-headed ant invasion. In doing so, my work will yield information important for understanding the ecology and conservation of lions—listed as “Vulnerable” by the IUCN—in post-invasion landscapes.

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