Aerobic dive limit in short-finned pilot whales Globicephala macrorhynchus: an assessment of behavioral criteria

Aerobic dive limits (ADLs) are a useful paradigm for assessing marine mammal diving ability. Given the allometry of total body oxygen stores and metabolic rate, larger animals should have increased diving capacities and thus elevated ADLs. The short-finned pilot whale Globicephala macrorhynchus is a deep-diving species with pronounced sexual size dimorphism, and individuals are regularly found in size-mixed groups. Therefore, we asked how body size constrains dive durations in this species and whether behavioral ADL (bADL), estimated as the 95th percentile of dive duration, is a useful measure of physiological ADL. We analyzed 30169 dives from 45 animals tagged with satellite-linked recorders off Cape Hatteras, North Carolina, and Jacksonville, Florida, USA, and determined a species-level bADL of 18.8 min and individual bADLs ranging from 13.9 to 22.1 min. To assess the influence of size on bADL, we estimated the body lengths of 19 whales from dorsal fin measurements. Body length did not fully explain intraspecific bADL variation, but similar dive distributions and lower bADL variance between animals tagged together indicated a potential effect of group membership. Moreover, individuals in Cape Hatteras had a significantly lower median bADL than those in Jacksonville, suggesting location may influence dive durations. These results indicate the potential impact of social and location-specific factors on bADL estimates in a deep-diving, sexually dimorphic species.