Optimising the timing of visual surveys of crabeater seal abundance: haulout behaviour as a consideration
Colin SouthwellAustralian Antarctic Division, Department of Environment and Heritage, Channel Highway, Kingston, Tas. 7050, Australia. Email: colin.southwell@aad.gov.au
Wildlife Research 32(4) 333-338 https://doi.org/10.1071/WR04085
Submitted: 24 September 2004 Accepted: 6 May 2005 Published: 5 July 2005
Abstract
The most practical means of estimating pack-ice seal abundance is by conducting visual surveys from ships and aircraft. However, only those seals hauled out on the ice are ‘available’ to such surveys, and additional information on haulout behaviour is required to adjust counts of seals on the ice to estimate the total population size. Consideration of the optimal time to undertake visual surveys with respect to availability is important to ensure that bias and uncertainty in the abundance estimate are minimised for a fixed survey effort. In order to assess the optimal time for conducting visual surveys of crabeater seals (Lobodon carcinophaga), satellite-linked dive recorders were attached to 24 adult seals in the pack-ice off east Antarctica to record haulout behaviour over a 4-month period from mid-September to mid-January. The optimal time for visual surveys within these four months was December to mid-January (after the pupping season) when a high, relatively constant proportion of seals were hauled out over a period of 6–7 h during daylight, and when variation in haulout behaviour between seals was low. Despite the necessity for breeding seals to haul out continuously for extended periods during the pupping season, this was not a preferred time for visual surveys because variability in haulout behaviour between breeding and non-breeding seals was high. The efficiency of surveys before pupping was limited by the relatively short time during daylight when both the proportion of seals hauled out was high and variability in haulout behaviour among seals was small.
Acknowledgments
This work extended over several Australian National Antarctic Research Expedition voyages on the RSV Aurora Australis from 1994/95–1999/00. I thank the ship captains and crews, helicopter crews and voyage management teams on all these voyages for logistical and management support. The safe sedation of seals under difficult circumstances was achieved with the expertise and skill of several veterinary anaesthetists to whom I very grateful: Mark Tahmindjis, Michael Lynch, Damien Higgins, Julie Barnes, Heather Gardner, Karen Viggers and Raina Plowright. Numerous expeditioners provided assistance in the capture and handling of seals, while others waited on board the Aurora Australis over many extended capture sessions; I thank everyone for their enthusiasm and/or patience. This work was undertaken under permits of the Commonwealth of Australia Antarctic Seals Conservation Regulations and was approved by the Antarctic Animal Ethics Committee.
Bengtson, J. L. , and Cameron, M. F. (2004). Seasonal haulout patterns of crabeater seals (Lobodon carcinophaga). Polar Biology 27, 344–349.
| Crossref | GoogleScholarGoogle Scholar |
Nordǿy, E. S. , Folkow, L. , and Blix, A. S. (1995). Distribution and diving behaviour of crabeater seals (Lobodon carcinophagus) off Queen Maud Land. Polar Biology 15, 261–268.
Nicol, S. , Constable, A. , and Pauly, T. (2000). Estimates of circumpolar abundance of Antarctic krill based on recent acoustic density measurements. CCAMLR Science 7, 87–99.
Siniff, D. B. , Stirling, I. , Bengtson, J. L. , and Reichle, R. A. (1979). Social and reproductive behavior of crabeater seals (Lobodon carcinophagus) during the austral spring. Canadian Journal of Zoology 57, 2243–2255.
Southwell, C. J. (2004). Satellite dive recorders provide insights into the reproductive strategies of crabeater seals (Lobodon carcinophagus). Journal of Zoology 264, 399–402.
| Crossref | GoogleScholarGoogle Scholar |
Southwell, C. , Kerry, K. , Ensor, P. , Woehler, E. J. , and Rogers, T. (2003). The timing of pupping by pack-ice seals in east Antarctica. Polar Biology 26, 648–652.
| Crossref | GoogleScholarGoogle Scholar |
Tahmindjis, M. A. , Higgins, D. P. , Lynch, M. J. , Barnes, J. A. , and Southwell, C. J. (2003). Use of a pethidine and midazolam combination for the reversible sedation of crabeater seals (Lobodon carcinophagus). Marine Mammal Science 19, 581–589.
