Home ranges and diving behavior of endangered New Zealand sea lions along the Catlins coast of South Island, New Zealand

Abstract

New Zealand sea lions (NZSL, Phocarctos hookeri) were extirpated from mainland New Zealand during pre-European subsistence hunting. They began reoccupying South Island in 1994, and the newest breeding colony arose in 2006 along the Catlins Coast on southeastern South Island and currently consists of <10 individuals. The goal of this study was to use animal-borne satellite telemeters and miniature data recorders (MDRs) to determine home ranges, three-dimensional movements, and foraging strategy of female NZSL along the Catlins Coast during the austral winter of 2019. Total home ranges were small (97 km2) and primarily restricted to nearshore areas. Dives were shallow (8.9 m), short in duration (1.4 min), and had a mean swimming speed of 1.5 m s−1. We identified three dive types based primarily on total dive duration, mean maximum depth, total distance swam, and path linearity. The estimated at-sea metabolic rate varied among dive types because of differences in flipper stroke frequency and swim speed. Female NZSL along the Catlins Coast have smaller home ranges and make shorter foraging trips compared with females in the Auckland Islands, and suitable habitat for breeding and prey availability along the southeast coast are encouraging for future population growth.