Population dynamics and anthropogenic threats to New Zealand fur seal (Arctocephalus forsteri) in New Zealand : a thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Veterinary Science at Massey University, Palmerston North, Aotearoa New Zealand

Abstract

New Zealand fur seals (Arctocephalus forsteri; ‘NZFS’) are New Zealand’s most encountered pinniped. However, substantial gaps exist in the knowledge of their abundance and distribution. This study provides NZFS abundance and distribution data for Kaikōura and Banks Peninsula and investigates anthropogenic risks in both locations. Additionally, the thesis undertakes the first nationwide NZFS abundance estimate in ca. 50 years. The Kaikōura population study was the first since the 2016 earthquake. Kaikōura’s NZFS population has grown and spread post-earthquake, with an upper population estimate of 21,560 – 28,327 NZFS in the 2022/23 breeding season. However, pup production at Ōhau Point, the most impacted colony, has not grown, and breeding distribution has changed significantly. Following earthquake damage, State Highway 1 (SH1), which runs close to NZFS colonies, was reconstructed. This study detected an almost fivefold increase in the annual number of NZFS recorded on SH1 from 2012 – 2022, compared to 1996 – 2005. Ten statistically significant NZFS incident clusters were located, representing 89% of the incidents. Cluster location shifted following post-earthquake road reconstruction. Monthly NZFS incident numbers were significantly positively associated with traffic and windspeed, and significantly negatively associated with temperature and rainfall. Road-abutting NZFS breeding explained most of the spatial variation in NZFS incidents. An abundance estimate of 13,147 – 17,675 NZFS was calculated for Banks Peninsula in 2023/24, and 25 previously unrecorded colonies were assessed. This study considered response strategies for an oil spill impacting Banks Peninsula’s NZFS, as the region is classified as ‘high risk’ for such incidents. Priority response strategies include preventing oil from reaching colonies, and hazing individuals away from waterborne slicks. From the most recently available count data, a minimum nationwide population estimate of 131,338 – 168,269 NZFS was calculated. Using recent counts and stage-structured population modelling, a more reliable estimate of 181,646 – 239,473 NZFS was calculated, a substantial increase on the most cited nationwide abundance figure, 100,000 NZFS. This thesis’ population findings provide useful baselines and highlight the need for improved NZFS population monitoring. This is particularly important due to the changing human-NZFS relationship, evidenced by the Kaikōura road reconstruction and the risk of oil spills in Banks Peninsula.