Sperm whales exhibit variation in echolocation tactics with depth and sea state but not naval sonar exposures
Abstract
Auditory masking by anthropogenic noise may impact marine mammals relying on sound for important life functions, including echolocation. Animals have evolved antimasking strategies, but they may not be completely effective or cost‐free. We formulated seven a priori hypotheses on how odontocete echolocation behavior could indicate masking. We addressed six of them using data from 15 tagged sperm whales subject to experimental exposures of pulsed and continuous active sonar (PAS and CAS). Sea state, received single‐pulse sound exposure level (SELsp), whale depth and orientation towards surface, and sonar were considered as candidate covariates representing different masking conditions. Echolocation behavior, including buzz duration and search range, varied strongly with depth. After controlling for depth and angle to the surface, the likelihood of buzzing following a click train decreased with sea state (t = −7.3, p sp, except reduced buzzing consistent with previously reported feeding cessation (t = −2.26, p = .02). A potential Lombard effect was detected during echolocation with sea state and SELsp, despite off‐axis measurement and right‐hand censoring due to acoustic clipping. The results are not conclusive on masking effects on sperm whale echolocation, highlighting challenges and opportunities for future anthropogenic masking studies.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 06, 2021
- Source ID
- 10.1111/mms.12890
Entities
People
- Alexander M. Von Benda‐beckmann
- Benjamin Benti
- Frans-Peter A Lam
- Ilias Foskolos
- Jacqueline Bort
- Kalliopi C. Gkikopoulou
- Miguel Neves
- Nicoletta Biassoni
- Patrick J O Miller
- Paul J. Wensveen
- Peter Tyack
- Petter H. Kvadsheim
- Saana Isojunno
- Viivi Pöyhönen
Organizations
- Aarhus University
- Netherlands Organisation for Applied Scientific Research
- Norwegian Defence Research Establishment
- Pacific Biological Station
- Strategic Environmental Research and Development Program
- United States Navy
- University of La Rochelle
- University of St Andrews