Movements and home ranges of monk seals in the main Hawaiian Islands

Hawaiian monk seals (Neomonachus schauinslandi) began recolonizing the main Hawaiian Islands (MHI) roughly 20 yr ago. The species' abundance is still declining, but the subpopulation in the MHI is increasing by 6.5% per year. This difference may be due to differences in prey availability or habitat quality between the northwest (NWHI) and main Hawaiian Islands, which could be reflected in the movements and behavior of the seals. For example, foraging trip durations may be shorter in areas with higher forage quality. From 2007 to 2014 we deployed GPS phone tags on the islands of Molokai (n = 7), Kauai (n = 6), and Oahu (n = 6) to study movements and dive behavior. Foraging trips typically lasted 0.57 d (IQR: 0.34-0.83) and seals traveled 18 km (IQR: 10.2-30.5) per trip. Seals began benthic dives shortly after entering the water, with most dives to depths of 12-32 m. The median 95% and 50% kernel density isopleths for seals in the MHI were 149.2 km(2) and 23.2 km(2), respectively. The duration and distance of foraging trips in the MHI were shorter than that observed in other studies from the NWHI, suggesting that foraging habitat is currently better in the MHI.