Publication Date

Fall 2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Birgitte McDonald; Scott Hamilton; Holder Klinck

Abstract

Understanding how marine mammals respond to and recover from acoustic stressors is crucial if underwater noise increases. The use of an animal-borne biologger that combines a speaker with a motion sensor allows for the collection of whole-dive and fine-scale data over repeated exposures under identical experimental parameters. This study determined whether northern elephant seals (Mirounga angustirostris), a model for deep-diving marine mammals, exhibited a stereotypical behavioral response when exposed to killer whale whistles, an acoustic stressor. I examined changes in dive characteristics, measured duration of altered response, and observed behavior in response to repeated exposures. When exposed to the playback on ascent, the elephant seals performed an escape response consisting of a dive inversion during which they increased activity and displayed more variation in swimming direction. However, the seals returned to baseline diving behavior immediately after the exposure dives, suggesting they recover quickly from disturbance. After repeated exposures, the seals continued to perform dive inversions but reduced the extent of their responses over time. Even though northern elephant seals appear to recover quickly from this acoustic stressor, the initial strong behavioral response still causes an increase in energy expenditure that could be detrimental over time, especially if they are continuously faced with disturbances. Integrating behavioral responses with physiological measurements will help us fully comprehend how these animals change their diving behavior in response to increased sounds in the ocean.

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