Abstract
Marine mammals navigate their environment both horizontally and vertically, adding an additional layer of complexity to understanding their behavior and developing effective conservation strategies. Here, we use data from 14 tagged common bottlenose dolphins ( Tursiops truncatus ) from Hawai'i to explore how their diving behavior varies in response to temporal and demographic variables. Overall mean dive depth (for dives ≥ 50 m) was 206 m (max = 896 m), and duration was 5.9 min (max = 13.6 min). However, individual variation was considerable and explained most of the variation in dive depths and durations. Dive rates varied between diel periods, with rates at night more than double those during the day. Dive depths and durations also varied between diel periods, with animals generally conducting their deepest and longest dives during dusk and their shortest and shallowest dives at night. Regular dives to or close to the seafloor occurred in depths of up to 800 m, but animals spent the majority of their time in the top 50 m of the water column. These findings represent the first baseline data on diving behavior for this species in Hawai'i and will be critical in evaluating potential impacts stemming from planned marine infrastructure development.