Kinematics of terrestrial locomotion in harbor seals and gray seals: Importance of spinal flexion by amphibious phocids

Abstract

Pinnipeds are amphibious mammals with flippers, which function for both aquatic and terrestrial locomotion. Evolution of the flippers has placed constraints on the terrestrial locomotion of phocid seals. The detailed kinematics of terrestrial locomotion of gray (Halichoerus grypus) and harbor (Phoca vitulina) seals was studied in captivity and in the wild using video analysis. The seals exhibited dorsoventral undulations with the chest and pelvis serving as the main contact points. An anteriorly directed wave produced by spinal flexion aided in lifting the chest off the ground as the fore flippers were retracted to pull the body forward. The highest length-specific speeds recorded were 1.02 BL/s for a gray seal in captivity and 1.38 BL/s for a harbor seal in the wild. The frequency and amplitude of spinal movement increased directly with speed, but the duty factor remained constant. Substrate did not influence the kinematics except for differences due to moving up or down slopes. The highly aquatic nature of phocids seals has restricted them to locomote on land primarily using spinal flexion, which can limit performance in speed and duration.

Axial allometry in a neutrally buoyant environment: effects of the terrestrial‐aquatic transition on vertebral scaling

“…Pinnipeds move much less effectively on land than in the water. Although otariids are able to raise their bodies off the ground by rotating their hind feet during short bursts of galloping or bounding gaits (Beentjes, ), phocids are unable to lift the trunk at all and move on land using spinal undulation (Garrett & Fish, ). Thus, we suggest that pinnipeds are adapted primarily to a buoyant environment and that the thoracolumbar region should have a diminished role in body support; in turn, there should be reduced vertebral allometry relative to terrestrial taxa.…”

Evolutionary innovation and ecology in marine tetrapods from the Triassic to the Anthropocene

“…Quantitative functional morphology provides a means to quantify and compare performance and functional trade-offs, particularly in species that spend time both on land and in the water, such as snakes (29) and pinnipeds (40). Functional trade-offs can ultimately drive specialization and steer evolutionary convergence, as with repeated loss of flight among seabirds specialized for aquatic locomotion (41).…”

In vitro evaluation and in vivo use of a novel surgical stent to minimize suture pressure necrosis

“…The skin is therefore the holding layer in many species of marine mammals for wound and incision closure, and healing may be prolonged secondary to focal dermal necrosis from sutures or traumatic tissue handling. During postoperative recovery, the strong muscular activity during normal swimming, and, for pinnipeds (eg, seals, sea lions, and walruses) the method by which they slide their body against the ground when on land, places a tremendous amount of strain on wounds and incisions. These anatomical and locomotive attributes result in an increased risk for dehiscence and penetration of water into the wound or body cavity from their aquatic environment.…”