Sound the alarm: Exploring the effects of anthropogenic noise on attention, learning, and memory in Tursiops truncatus

Anthropogenic noise has become an increased concern amidst the continually rising levels as human activities expand across the globe. Cetaceans are particularly susceptible to the impacts of anthropogenic noise due to the sensitive hearing structures, acoustically focused communication, and their reliance on complex cognition (attention, learning, and memory). Disruptions in these cognitive systems are implicated as potential welfare concerns that are not well explored in both wild and professional care environments. Anthropogenic noise affects dolphin attention through a sensitization response to anthropogenic noise across facilities that hear noise normally. Dolphins (Tursiops truncatus) housed across pool, lagoon, and ocean exposed facility types responded with significantly different look duration responses to anthropogenic noise playbacks. Those housed in pool facilities investigated the sound source less than those that live in an environment with frequent anthropogenic noise events indicating an overall sensitization response to noise. Further, when anthropogenic noise types were compared across all facilities the dolphins did not respond differently to individual playback types. This indicates there is no overall habituation or sensitization profile by anthropogenic noise source. However, when tested individually by facility there was a difference in response to anthropogenic noise types. Additionally, the anthropause resulting from the COVID-19 pandemic allowed for testing of attentional responses after a long cessation of sound produced by human activity. During the anthropause, dolphins spent more time responding to anthropogenic noise but less time vocally responding to the same noises. Attentional deficits from human noise affect task learning in dolphins, but only significantly more complex tasks were affected. Dolphins trained on novel behaviors in the presence of anthropogenic noise took longer to learn the more difficult novel behaviors learned without additional noise stimuli. When tested after a one-year training pause, dolphins recalled the easier match-to-sample task significantly better than the object-as-signal task. Further, dolphins recalled their task better when exposed to noise. However, this may be due to an order effect. Additionally, they exhibited the largest change in percentage correct between the end of their learning test and memory test when exposed to noise indicating a large variability in response. These studies are some of the first to look at the effects of anthropogenic noise on dolphin cognition and the dual process of sensitization and habituation in dolphins. Dolphins rely on complex cognition to navigate almost all aspects of their lives from social hierarchies to hunting techniques. Therefore, any cognitive deficits from attentional draw by sensitization threatens the welfare and health of populations in areas with increased presence of anthropogenic noise activities. These studies present the first granular look into the effects of anthropogenic noise on multiple facets of dolphin cognition and will aid in conservation and welfare efforts.