The relationship between two species of fur seals Arctocephalus Tropicalis (Gray) and A. Gazella (Peters) on Marion Island

Abstract

Subantarctic fur seals Arctocephalus tropicalis and Antarctic fur seals A. gazella are sympatric at the Prince Edward Is lands, and appear to be hybridizing. Adult males of both species and the interspecific hybrids can be distinguished using univariate and multivariate analyses of cranial measurements. The two species differed in the electrophoretic mobility of the serum protein, transferrin. The extent of hybridization appears to be limited with the hybrids representing 0,1% of the total fur seal population (34528 A. tropical is and 300-400 A. gazella). Although the seasonal haul-out patterns and breeding habitat preferences of these two species do differ, these differences do not appear to be sufficient to prevent hybridization. Differences 1n suckling periods and pup growth rates may be acting to limit hybridization through pup mortality of hybrids born to A. gazella females.