Meeting Abstract
In the transition from terrestrial to aquatic habits in marine mammals, there has been a change in morphology that has placed constraints on the ability of these animals to continue to function on land. The amphibious northern elephant seal, Mirounga angustirostris, is the second largest phocid seal reaching 2,300 kg. Although elephant seals are proficient swimmers and deep divers, their extreme size can limit terrestrial movement. The kinematics of terrestrial locomotion in northern elephant seals were analyzed from video recordings of animals observed on the beach of Año Nuevo State Reserve, CA. The seals moved by dorsoventral spinal flexions. The traveling spinal wave moved anteriorly along the body with the chest, pelvic region, and foreflippers serving as the contact points with the ground. The hind flippers were not used. The spinal wave and foreflippers were used to lift the chest off the ground as the body was pushed forward from the pelvis and the foreflippers were retracted to pull the body forward. Seals moved over land at 0.36–2.55 m/s. Frequency of spinal flexions displayed a direct significant relationship with speed. Contact with the ground differed between the foreflippers and pelvic region as the duty cycle ranged from 0.55–0.96 and 0.12–0.53, respectively. The duty cycle for both foreflippers and pelvic region decreased with increasing speed. The trade-off for the northern elephant seal has been that its massive size and morphology have well adapted it to an aquatic existence, but limited its locomotor performance (i.e., speed, endurance) on land.
