Social and thermoregulatory behaviour of the New Zealand fur seal, Arctocephalus forsteri (Lesson, 1828)
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Since 1871, when Darwin's first edition of The Descent of Man and Selection in Relation to Sex was published, there have appeared numerous studies of sexual dimorphism and sexual selection in fossil and extant taxa. Principles elucidated by Darwin on the choice of, and competition for mates, have since been supported by additional evidence, but is has become apparent that the causes and functions of sexual dimorphism are more diverse than Darwin envisaged (Huxley, 1938a, b). Published studies on sexual dimorphism in birds, fish, and arthropods are numerous, but there are remarkably few on mammals. The functioning of sexual selection is implicit, however, in the interpretation of such researches as those of Bannikov (1958) on the saiga antelope, Saiga tatarica, by Geist (1966a, b) on artiodactyls, and by Hall (1964) on primates. The objective of the present study was to examine the social behaviour of the New Zealand fur seal, Arctocephalus forsteri (Lesson), with emphasis on the role played by sexual dimorphism, and the relationship of social structure to thermoregulatory requirements and topography. This species, like all otariids, is polygynous and sexually dimorphic. It breeds in discrete, established colonies, is ashore in large numbers during the breeding season, and is readily observed. Territorial males fast while ashore, and normally do not leave their stations until defeated by challenging males or until the end of the breeding season. Their social contacts during the reproductive period can therefore be readily monitored. Individually recognizable animals are a requisite for successful field behaviour studies, and it was known from work on Zalophus (Peterson and Bartholomew, 1967), Callorhinus (Bartholomew and Hoel, 1953; Bartholomew, 1953; Kenyon, 1960; Peterson, 1965, 1968), Eumetopias (Gentry, 1970; Sandegren, 1970), A. p. pusillus (R. W. Rand, 1967) and A. townsendi (Peterson and Ramsey, 1968; Peterson et al. 1968), that many animals can be individually recognized by natural scars and marks, or can be approached and marked by paint, dye, or hair-clipping (see Appendix A for nomenclature used in this text). Although numerous publications have appeared on the general biology and behaviour of the genus Arctocephalus, none has approached the degree of refinement of studies on the reproductive and social behaviour of the two northern otariids Callorhinus (Peterson, 1965) and Eumetopias (Gentry, 1970; Sandegren, 1970).