Delphinid behavioral responses to incidental mid-frequency active sonar

TitleDelphinid behavioral responses to incidental mid-frequency active sonar
Publication TypeJournal Article
Year of Publication2014
AuthorsHenderson E.E, Smith M.H, Gassmann M., Wiggins SM, Douglas A.B, Hildebrand JA
JournalJournal of the Acoustical Society of America
Volume136
Pagination2003-2014
Date Published2014/10
Type of ArticleArticle
ISBN Number0001-4966
Accession NumberWOS:000345977400064
Keywordsabundance; bottle-nosed-dolphin; classification; common dolphin; ecology; marine mammals; sampling methods; vocalizations; whales; whistles
Abstract

Opportunistic observations of behavioral responses by delphinids to incidental mid-frequency active (MFA) sonar were recorded in the Southern California Bight from 2004 through 2008 using visual focal follows, static hydrophones, and autonomous recorders. Sound pressure levels were calculated between 2 and 8 kHz. Surface behavioral responses were observed in 26 groups from at least three species of 46 groups out of five species encountered during MFA sonar incidents. Responses included changes in behavioral state or direction of travel, changes in vocalization rates and call intensity, or a lack of vocalizations while MFA sonar occurred. However, 46% of focal groups not exposed to sonar also changed their behavior, and 43% of focal groups exposed to sonar did not change their behavior. Mean peak sound pressure levels when a behavioral response occurred were around 122 dB re: 1 mu Pa. Acoustic localizations of dolphin groups exhibiting a response gave insight into nighttime movement patterns and provided evidence that impacts of sonar may be mediated by behavioral state. The lack of response in some cases may indicate a tolerance of or habituation to MFA sonar by local populations; however, the responses that occur at lower received levels may point to some sensitization as well. (C) 2014 Acoustical Society of America.

DOI10.1121/1.4895681
Integrated Research Themes: 
Student Publication: 
No