Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Acoustic behaviour of southern right whales in relation to numbers of whales present in Walker Bay, South Africa

Acoustic behaviour of southern right whales in relation to numbers of whales present in Walker... Estimating numbers of whales present in an area from recorded call rates could be a useful conservation tool. We recorded southern right whale Eubalaena australis vocalisations and presence in Walker Bay on the south coast of South Africa. In all, 45 sessions with synchronous acoustic and visual data were analysed to determine call rates directly (overall call rate, OCR) and in relation to the number of whales sighted (call rate per whale, CPW) and number of groups sighted (call rate per group, CPG). The OCRs were examined in the presence of varying numbers of whales, using a log-linear model to investigate the dependence of the call rate on whale density. The number of whales present exerted a strong quadratic effect on the OCR, which peaked at around 15 whales and decreased to a low rate as whale presence approached a maximum, for all calls combined and for four of their constituent 13 call types: a quadratic trend was present to varying degrees among the remaining call types. Both quadratic and linear trends were absent when OCR was assessed against number of groups present, possibly because group size increased with increasing density of whales. A linear regression on the CPW and CPG suggested that there was a negative inverse relationship with the number of whales and groups present respectively. These findings are important in that, while they preclude the estimation of absolute numbers from call rates, they imply that, under the conditions prevailing in Walker Bay, southern right whales were aware of the presence, arrival and departure of other animals in their vicinity and adjusted their vocal behaviour accordingly. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png African Journal of Marine Science Taylor & Francis

Acoustic behaviour of southern right whales in relation to numbers of whales present in Walker Bay, South Africa

Hofmeyr-Juritz, LH; Best, PB
African Journal of Marine Science , Volume 33 (3): 13 – Nov 1, 2011
Download PDF

Acoustic behaviour of southern right whales in relation to numbers of whales present in Walker Bay, South Africa

Abstract

Estimating numbers of whales present in an area from recorded call rates could be a useful conservation tool. We recorded southern right whale Eubalaena australis vocalisations and presence in Walker Bay on the south coast of South Africa. In all, 45 sessions with synchronous acoustic and visual data were analysed to determine call rates directly (overall call rate, OCR) and in relation to the number of whales sighted (call rate per whale, CPW) and number of groups sighted (call rate per...
Loading next page...
 
/lp/taylor-francis/acoustic-behaviour-of-southern-right-whales-in-relation-to-numbers-of-0MpCLG9gPS
Publisher
Taylor & Francis
Copyright
Copyright Taylor & Francis Group, LLC
ISSN
1814-2338
eISSN
1814-232X
DOI
10.2989/1814232X.2011.637616
Publisher site
See Article on Publisher Site

Abstract

Estimating numbers of whales present in an area from recorded call rates could be a useful conservation tool. We recorded southern right whale Eubalaena australis vocalisations and presence in Walker Bay on the south coast of South Africa. In all, 45 sessions with synchronous acoustic and visual data were analysed to determine call rates directly (overall call rate, OCR) and in relation to the number of whales sighted (call rate per whale, CPW) and number of groups sighted (call rate per group, CPG). The OCRs were examined in the presence of varying numbers of whales, using a log-linear model to investigate the dependence of the call rate on whale density. The number of whales present exerted a strong quadratic effect on the OCR, which peaked at around 15 whales and decreased to a low rate as whale presence approached a maximum, for all calls combined and for four of their constituent 13 call types: a quadratic trend was present to varying degrees among the remaining call types. Both quadratic and linear trends were absent when OCR was assessed against number of groups present, possibly because group size increased with increasing density of whales. A linear regression on the CPW and CPG suggested that there was a negative inverse relationship with the number of whales and groups present respectively. These findings are important in that, while they preclude the estimation of absolute numbers from call rates, they imply that, under the conditions prevailing in Walker Bay, southern right whales were aware of the presence, arrival and departure of other animals in their vicinity and adjusted their vocal behaviour accordingly.

Journal

African Journal of Marine Science – Taylor & Francis

Published: Nov 1, 2011

Keywords: acoustics; call rates; Eubalaena australis; log-linear model; relative abundance; vocalisations

There are no references for this article.