Quantifying the effect of anthropogenic noise sources on cetacean fine-scale diving biomechanics and
Abstract
Behavioral Response Studies (BRS) have shown that cetaceans react to anthropogenic sounds such as navy sonar in ways that can lead t,o increased energy expenditure, e.g., increasing swimming speed, extending dives and avoiding the location of exposure. Beaked whale,s are the most sensitive group documented so far, and it is hypothesized that navy sonar can cause individuals to enter an abnormal,physiological state leading to lethal strandings. Locomotion costs for searching and capturing prey are the most significant compone,nt of cetaceans? total energetic costs during baselinebehavior, but locomotion costs could increase considerably due to avoidance. U,nderstanding energetic costs and how they vary with context is critical for constructing robust Population Consequences of Acoustic,Disturbance (PCOD) models. Behavioral response studies of cetaceans have extensively used the Overall Dynamic Body Acceleration (ODB,A) as a proxy for energy expenditure (EE), to identify and characterize avoidance responses to sonar. However, ODBA is dependent on,body size and activity. Specifically, this method overestimates the EE in large animals thus preventing comparative analyses and can,not identify periods of higher swimming speed in biganimals. In addition, quantitative data on how beaked whales manage gas volumes,during dives is required to test whether a decompression sickness-like syndrome can occur as a by-product of a strong behavioral res,ponse to noise.We propose to analyze existing BRS data from 10 different species including 7 toothed whales (of which 4 are beaked w,hale species) and 3 baleen whales, all fitted with DTAG biologging devices. This will allow us to quantify the effects of simulated,ns. We hypothesize that anthropogenic sounds lead to a change in behavior that results in increased EE with respect to periods of ba,seline behavior. Anincrease in locomotion-related EE could be caused by an increase in dive duration, swimming speed, and/or by adop,ting a more energetically demanding gait, such as the recently described fast and strong ?B-strokes? in beaked whales. B-strokes are, hypothesized to be associated with recruitment of fast-twitch fibers when oxygen stores dwindle in long dives. To test our hypothes,is, we will use a recently developed method for kinematic analysis, the ?magnetometer method? that will allow us to calculate a prox,y for EE that overcomes the limitations of ODBA. We will also use a recently developed method to estimate the relative diving lung v,olume at the beginning of the dive, as an indicator of intended dive depth and duration. If EE increases, so will oxygen consumption, and therefore an earlier use of possible anaerobic strategies such as the use of B-strokes when oxygen stores are nearly exhausted., Using diving lung volume at the start of the dive, we will also investigate if there is a change in the intended dive depth (e.g.,,switch from a shallow to a deep dive) due to sonar exposure in those cetacean species that perform distinctive short-and-shallow and, longand-deep dives (e.g., beaked whales, pilot whales and sperm whales). Together, these results will allow us to assess whether mo,re behaviorally responsive species (i.e., beaked whales) show more energetically expensive responses, i.e., longer diving durations,with the appearance of faster and stronger gaits earlier than expected. With this project we aim to fill ga,e effect of anthropogenic noise on cetacean fine-scale biomechanics and theirenergetic and physiological implications, to better und,erstand whether some species are more susceptible to disturbance than others.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 08, 2022
- Source ID
- N000142212735
Entities
People
- Fleur Visser
Organizations
- Office of Naval Research
- United States Navy