Parasites and infectious diseases can have profound effects on their hosts, yet relatively little is known about how parasites influence animal behavior. The work will address three fundamental questions: (1) Does individual infection risk vary with mating status and behavior? (2) Do parasites drive variation in mating tactics by influencing individual mating decisions, behavior, and mating success? (3) What are the mechanisms underlying associations between mating behavior and parasite infection? To answer these questions, associations between behavior, physiology and gastrointestinal nematode parasitism in the African antelope, Grant's gazelle (Gazella granti), will be studied. Taking advantage of natural variation in the behavior of male gazelles, the study will examine whether higher parasite infection levels are associated with differences in male mating behavior. In addition, experimental manipulation of male parasite loads will test the effect of parasites on individual mating decisions and mating success. Finally the work will use field and physiological studies to investigate whether reproductive behavior modifies male exposure and susceptibility to parasites. The study results will reveal the extent to which parasites shape behavioral strategies observed in host populations, shedding light on the evolutionary significance of complex animal behaviors. The results of this study will also make a timely contribution to knowledge of how animal behavior may change in response to increasing parasite pressure. The project will provide numerous educational opportunities for undergraduate and graduate students. Biology students from both the U.S.A. and Kenya will gain hands-on training in the fields of disease ecology and behavioral ecology. American students will obtain international research experience working at the study site in Kenya; and students from both countries will have unique opportunities for academic and cultural exchange. This award is co-funded by NSF's Office of International Science and Engineering.
Intellectual merit: Parasites are ubiquitous parts of the environment, and they affect animal behavior. Behavior, in turn, affects animals' risk of parasite infection. This project examined the reciprocal effects of parasites on behavior and behavior on parasites focusing on reproductive behavior in male Grant's gazelles. The Grant's gazelle is a common East African antelope in which males either defend territories to attract mates or reside in roving bachelor herds. By tracking individual males through time as they moved between reproductive states (bachelor to territorial male or vice versa), this study showed that the accumulation of gastrointestinal parasites is an important cost of territorial behavior. This cost accrues because territorial behavior is associated with changes in parasite exposure and susceptibility that enhance infection risk. For instance, territorial males have higher testosterone levels, and this hormone is associated with the suppression of certain immune responses. Territorial males also feed in habitats that are more contaminated with parasites when compared to bachelor males, and this increases their contact with parasites. These results support the idea that male behavior is directly associated with increases in parasite infection. In addition, experimental manipulation of parasite loads in territorial males revealed that parasites suppress agonistic behaviors that are crucial for maintaining a territory. Taken together, study results point to a parasite-mediated feedback loop where territoriality promotes the accumulation of parasites in males, but these parasites suppress the very behaviors required for territory maintenance. Overall, this study provides evidence of a dynamic interplay between parasites and behavior that may help explain high levels of behavioral flexibility observed in Grant's gazelle, and in other animal species more generally. Broader impacts: A key broader impact of this project was student training. Over twenty students (including undergraduate, veterinary and graduate students) and seven postgraduates received training as part of the project. In addition, ten Kenyan undergraduates participated in field courses held at the project study site and designed as part of the educational component of the project. As part of the project training activities, U.S. students worked side-by-side with Kenyan students to learn and conduct research on animal behavior and disease ecology fostering bi-national collaborative academic and cultural exchange. A second component of the project's broader impacts involved fostering awareness of the important connections between animal behavior and parasites and microbes, both inside and outside of the discipline. This was accomplished through the publication of several synthetic review papers and the organization of two symposia at national meetings.
