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Marine Ecology Progress Series

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MEPS 412:293-304 (2010)  -  DOI:

Segregation in a sexually dimorphic mammal: a mixed-effects modelling analysis of diving behaviour in southern elephant seals

Trevor McIntyre1*, Cheryl A. Tosh1, Joachim Plötz2, Horst Bornemann2, Marthán N. Bester1

1Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
2Alfred Wegener Institute for Polar and Marine Research, PO Box 120161, 27515 Bremerhaven, Germany

ABSTRACT: Sexual segregation in habitat use occurs in a number of animal species, including southern elephant seals, where differences in migration localities and dive behaviour between sexes have been recorded. Due to the extreme sexual size dimorphism exhibited by southern elephant seals, it is unclear whether observed differences in dive behaviour are due to increased physiological capacity of males, compared to females, or differences in activity budgets and foraging behaviour. Here we use a mixed-effects modelling approach to investigate the effects of sex, size, age and individual variation on a number of dive parameters measured on southern elephant seals from Marion Island. Although individual variation accounted for substantial portions of total model variance for many response variables, differences in maximum and targeted dive depths were always influenced by sex, and only partly by body length. Conversely, dive durations were always influenced by body length, while sex was not identified as a significant influence. These results support hypotheses that physiological capability associated with body size is a limiting factor on dive durations. However, differences in vertical depth use appear to be the result of differences in forage selection between sexes, rather than a by-product of the size dimorphism displayed by this species. This provides further support for resource partitioning and possible avoidance of inter-sexual competition in southern elephant seals.

KEY WORDS: Sexual segregation · Sexual dimorphism · Dive behaviour · Southern elephant seals · Linear mixed-effects models · Mirounga leonina

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Cite this article as: McIntyre T, Tosh CA, Plötz J, Bornemann H, Bester MN (2010) Segregation in a sexually dimorphic mammal: a mixed-effects modelling analysis of diving behaviour in southern elephant seals. Mar Ecol Prog Ser 412:293-304.

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