A tale of two singers: how do bats and bird mixed-flocks respond to petroleum industry noise in the Ecuadorian Amazon

Abstract

Industrial noise can have a significant impact on animal groups that rely on acoustic communication for fundamental survival activities. Our research focuses on two of these groups: insectivorous bats, which use ultrasound to navigate and find food; and mixed flocks of insectivorous birds, that rely on vocalizations to communicate about foraging direction and potential threats. We conducted in situ experiments in the Yasuni Biosphere Reserve in the Ecuadorian Amazon to understand the immediate and long term effects of industrial noise on behaviour, habitat use and local diversity. We characterized bats and birds vocalizations, and the industrial noise profile, both in ultrasound and audible frequencies. Experiments were performed using pure tone sounds representative of the industrial noise acoustic profile. Moreover, experiments included behavioral response characterization and acoustic transmission modeling. Our results suggest, in both groups, the immediate response is avoidance. In the long term, the effects included a change on habitat use, and modification on community composition. These effects are proportional to how similar is the noise to the frequencies commonly used by the animals and how much noise the habitat itself absorbs. Modeling and technology development are the next steps to further understand these effects and how to mitigate them.