Regional diving behavior of Pacific Arctic beluga whales Delphinapterus leucas and possible associations with prey

Navigating under sea ice promotes rapid maturation of diving physiology and performance in beluga whales

“…Although there are data on the at-sea swimming, diving and habitat use of beluga whales (e.g. Smith, 1992, 1999;Martin et al, 1993Martin et al, , 1998Martin et al, , 2001Heide-Jørgensen et al, 1998, 2001Kingsley et al, 2001;Citta et al, 2013;Hauser et al, 2014Hauser et al, , 2015, these studies only provide a glimpse of their capabilities and behaviors within the context of their current ecosystem. Knowledge of age-and sex-class limits for maximum dive duration and depth (Table 3), as well as the amount of submergence time at a given depth (Fig.…”

“…When comparing our theoretical assessment of maximum dive duration and depth with the foraging behaviors of free-ranging beluga whales (e.g. Smith, 1992, 1999;Martin et al, 1993Martin et al, , 1998Martin et al, , 2001Heide-Jørgensen et al, 1998, 2001Kingsley et al, 2001;Citta et al, 2013;Hauser et al, 2014Hauser et al, , 2015, we gain insight into how closely belugas are operating at their physiological capacity. Our estimates for maximum dive capacity (assuming a diving metabolism of 2× Kleiber BMR; Table 3) for a mature 754 kg female and 1016 kg male were 12.58 and 13.53 min, respectively (Table 3), and approximated the mean dive duration of 13.1 min recorded for free-ranging beluga whales (Martin and Smith, 1992) but were less than the maximum dive duration of free-ranging beluga whales (21-22.9 min; Martin and Smith, 1992;Citta et al, 2013).…”

“…This assumption is based on maximum swim speed (swim speed range: 0.25-2.0 m s −1 ) estimated for diving belugas (Hauser et al, 2015) and the average of the maximum descent and maximum ascent rates (descent rate range: 1.43-2.20 m s −1 ; ascent rate range: 1.23-1.84 m s −1 ) measured for diving belugas (Martin and Smith, 1992). Using the maximum ascent and descent rate provided the best estimate of maximum dive depth because beluga whales increase ascent and descent speeds with increasing dive depth (HeideJørgensen et al, 1998;Martin and Smith, 1999;Laidre et al, 2003;Hauser et al, 2015). In addition, this speed approximates the minimum cost of transport speed measured for dolphins (T. truncatus), which by definition elicited the lowest oxygen consumption rate (Williams et al, 1993).…”

“…Submerged search time was calculated for depths of 200 and 300 m, as ECS belugas typically feed at 200-300 m, where cod reside in the water column (Citta et al, 2013;Hauser et al, 2015). Belugas have also been observed to have extended occupancy times at 200-400 m and >400 m (Hauser et al, 2015); thus, submergence times at 400 m, as well as the maximum achievable dive depths, which assume a touch and go dive with zero bottom time, were calculated. Subsurface submergence time, as is required for traveling below sea ice, assumed no transit time to depth, and was therefore equivalent to the cADL.…”

“…Dive performance limits were compared with diving behaviors of freeranging belugas (e.g. Martin and Smith, 1992;Citta et al, 2013;Hauser et al, 2015) to ascertain how closely belugas approximate their physiological capacity, and so determine whether belugas will have the flexibility to alter foraging behaviors (dive for longer durations and to deeper depths). Predicting the resiliency of belugas to environmental perturbations is especially important because some populations of beluga are already critically endangered, such as Cook Inlet belugas (Hobbs and Shelden, 2008).…”