Date of Award

Spring 5-12-2017

Degree Type

Honors Thesis


Zoology and Physiology

First Advisor

Anne-Marie Claire Hodge


When mammals select for fleshy fruits of introduced species, subsequent seed dispersal may increase a potential invader’s rate of establishment and spread. We assessed whether olive baboons (Papio anubis) select for the fruits of an invasive prickly pear cactus (Opuntia stricta) on the Laikipia Plateau in Kenya. Baboons function as seed dispersers for native flora across many regions of Africa. By eating the fleshy fruits of O. stricta, they also facilitate the establishment and spread of the cactus. We collected scats from eight baboon roosts; the seeds in the scats were identified to species and then counted and weighed. To determine fruit availability, we conducted vegetation surveys of the baboon roosts and quantified fruits per cactus. Using a two-sample t-test, we compared the cactus fruit availability, and the proportion of individual scats’ masses that were O. stricta seeds, between 2014 and 2016. Fruit availability decreased substantially between 2014 and 2016, however, the proportion of 0. stricta seeds in the scats did not decrease significantly. Following such a marked decline in O. stricta fruits in 2016, we would expect the proportion of 0. stricta seeds in the baboons’ scats to decrease proportionately. Our scat data, however, indicates baboons appear to be consuming a disproportionate amount of 0. stricta relative to availability. This has important implications for both management of O. stricta around the world and our understanding of native mutualisms between baboons and the native flora on the Laikipia Plateau.