AbstractsBiology & Animal Science

New Zealand sea lion abundance, demographics and movements in southern New Zealand

by Nathan Colin Wheeler McNally

Institution: University of Otago
Year: 0
Keywords: New Zealand sea lion; Phocarctos hookeri; Hooker's; sea lion; Campbell Island; The Snares; abundance; pup; Catlins; marine mammal; conservation; status; population
Record ID: 1313677
Full text PDF: http://hdl.handle.net/10523/5412


This study represents the first comprehensive survey of the New Zealand sea lion, Phocarctos hookeri populations at Campbell Island, the first surveys in nearly 30 years at The Snares and the continuation of a monitoring program in the Catlins. The results from each of these study locations, increases the understanding of the population dynamics of the species. Photo-identification and mark recapture techniques were used to obtain a population estimate for male sea lions in the Catlins. There are approximately 63 males, and at least two females. Over the eighteen-month period of this study, July 1997 – January 1999, only five new identifications were made. The population in the Catlins continues to increase, but it appears it will remain a predominantly male non-breeding colony, in the short term at least. Photo-identification and mark recapture techniques were used to study the abundance and demography of sea lions at North East Island, The Snares during autumn 1997 and autumn 1998. In total 118 male sea lions were identified, with 63% of identifiable sea lions from 1997 being resighted in 1998. The population estimates for male sea lions were 234 (95% CI 187 to 293) males in 1997 and 255 (95% CI 187 to 348) males in 1998. The minimum estimate for females was 2 in 1997 and 7 in 1998. A single pup was recorded in 1997, but none in 1998. The Snares, despite records of occasional breeding spread over nearly 100 years, remains a non-breeding colony. Campbell Island is the only major breeding site for sea lions outside of the Auckland Islands. Minimum pup production was estimated at 78 for the 1997/98 breeding season, compared with the only previous estimate of 122 from 1991/92, and represents less than 5% of the total pup production for the species. Sea lions at Campbell Island have a widespread distribution, clumped at the coast with low densities inland. Local concentrations of sea lions were seen at Davis Point, Sandy Bay and both Northeast and Southeast Harbours. Isolated individuals were found up to 1.5km inland and at altitudes >250 m. Breeding females at Campbell Island are generally solitary and give birth inland, in contrast to the highly gregarious colonial rookeries seen on the coasts of the Auckland Islands. This study also presents the confirmation of an annual return migration by adult male sea lions based in Otago to the breeding colonies at the Auckland Islands.