Colony growth and pup condition of the New Zealand fur seal (Arctocephalus forsteri) on the Kaikoura coastline compared with other east coast colonies

Abstract

Abstract.Since its near extermination by sealing, the New Zealand fur seal (Arctocephalus forsteri) has been recolonising areas of its former range throughout New Zealand and Australia. This study examined fur seal population growth over four breeding seasons spanning 2002–05 at the Ohau Point and Lynch’s Reef colonies in Kaikoura and the Horseshoe Bay and Te Oka Bay colonies on Banks Peninsula, on the east coast of New Zealand. Estimates of pup numbers were made using mark–recapture techniques and condition indices were used to assess the body condition of pups in each colony. We found that the Ohau Point and Te Oka Bay colonies are growing exponentially (32% and 47% per annum respectively), reaching nearly 600 pups at Ohau Point and 300 pups at Te Oka Bay, whereas Horseshoe Bay appears stable. Pups born at Ohau Point are consistently heavier and in better condition than their Banks Peninsula counterparts despite the faster rate of growth observed at Te Oka Bay. An El Niño event in 2003 coincided with a drop in mass and condition at the Banks Peninsula colonies, but not at the Kaikoura colony. This discrepancy between colonies in response to environmental conditions suggests that colony-specific variables at Kaikoura may provide more favourable conditions for rearing pups than on Banks Peninsula.