Impact of Botfly Parasitism on the Behavior of Mantled Howler Monkeys

Parasitism, a widespread nutrient acquisition strategy among animals, results from a long evolutionary history where one species derives its metabolic needs from another. Parasites can significantly reduce host fitness, affecting reproduction, growth, and survivability. Vertebrate hosts exhibit defensive strategies against parasites, including "sickness behaviors" such as lethargy and self-grooming to remove ectoparasites. In addition, social animals may engage in "helping sick animals" behaviors, such as social grooming, to aid parasitized group members. Mantled howler monkeys (Alouatta palliata) parasitized by botfly larvae (Cuterebra baeri) exhibit subdermal nodules, which can be fatal under nutritional stress. This study investigates whether mantled howler monkeys display sickness behaviors or helping behaviors in response to C. baeri parasitism. Observations from July 2022 to April 2023 in La Flor de Catemaco, Mexico, revealed that parasitized individuals did not increase the frequency of self-directed (rub, scratch, and touch) nor received helping behaviors (social scratch and social touch) compared to non-parasitized ones. However, parasitized monkeys were more active, spending more time feeding and moving, likely to compensate for the metabolic costs of parasitism. This shift from energy conservation to energy acquisition strategies suggests a complex response to parasitism, emphasizing the need for further research on the energetic impacts of parasitism in this species. These preliminary findings suggest behavioral flexibility by mantled howler monkeys in coping with infection, indicating potential adaptive strategies to mitigate the adverse effects of parasitism.