Behavioral Ecology and Sociobiology

, Volume 59, Issue 2, pp 293–302

Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki)

  • Jochen B. W. Wolf
  • Göran Kauermann
  • Fritz Trillmich
Original Article

Abstract

In many sexually dimorphic species adult sexes tend to segregate socially, spatially, or in habitat use. Several hypotheses have been formulated regarding underlying mechanisms. We investigated terrestrial habitat use and sexual segregation in a tropical otariid, the Galápagos sea lion (Zalophus californianus wollebaeki), where most of the hypotheses can be ruled out a priori. Factors relating to thermoregulation and costs of locomotion were of prime importance for habitat use. Habitats directly adjacent to the sea, with simple structured flat surfaces, shade, and tide pools were most frequented, but sexes and age classes differed in their usage patterns. Sexual segregation, both spatial and by habitat was pronounced in the reproductive period (RP), but remained high during the nonreproductive period (NRP). A GLM model of habitat use showed that in both seasons adult males frequented habitat types that adult females and other age classes used much less. Males were most abundant in suboptimal inland habitats, which offered only shade for cooling. Females with newborns differed in habitat use from females with older offspring and lone females. Spatial and habitat segregation are explained most parsimoniously as by-products of social processes, primarily intrasexual competition and female avoidance of male harassment, linked to the polygynous mating system.

Keywords

Habitat choice Harassment Intrasexual competition Mating system Seal Sexual segregation Sexual size dimorphism 

Supplementary material

265_2005_42_MOESM1_ESM.pdf (90 kb)
Multiple Testing Adjustment

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Jochen B. W. Wolf
    • 1
  • Göran Kauermann
    • 2
  • Fritz Trillmich
    • 1
  1. 1.Animal BehaviourUniversity BielefeldBielefeldGermany
  2. 2.Statistics Consultancy UnitUniversity BielefeldBielefeldGermany

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