Body Condition and Allometry of Free-Ranging Short-Finned Pilot Whales in the North Atlantic

Abstract

To understand the effects of anthropogenic disturbance on the nutritional health of animals, it is important to measure and understand the morphometrics, allometrics, and body condition of the species. We examined the body shape, allometric relationships, and body condition of short-finned pilot whales (Globicephala macrorhynchus) in three locations across the North Atlantic. Using unmanned aerial vehicles, the body length (BL) and width (along the body axis) were measured from photographs of the dorsal side, while body height (dorso-ventral distance) was measured on the lateral side. Seventy-seven pilot whales were measured (mean ± SD), including 9 calves (BL 2.37 m ± 0.118), 31 juveniles (2.90 m ± 0.183), and 37 adults (3.72 m ± 0.440). The body shape was similar among reproductive classes, with the widest point being anterior of the dorsal fin (at 30–35% BL from the rostrum). The cross-sectional body shape of the whales was flattened in the lateral plane, which increased towards the peduncle and fluke. The rostrum-blowhole distance and fluke width increased linearly with BL. The estimated volumes of pilot whales ranged between 0.15 and 0.32 m3 for calves, 0.25 and 0.64 m3 for juveniles, and 0.46 and 1.13 m3 for adults. The body condition (residual of log-volume vs. log-length) ranged from −34.8 to +52.4%. There was no difference in body condition among reproductive classes or locations.