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

• Published in: Marine Mammal Science
• Main Authors: Garrett, Jennifer N., Fish, Frank E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: harbor seal; Phoca vitulina
• Online Access: http://dx.doi.org/10.1111/mms.12170; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fmms.12170; https://onlinelibrary.wiley.com/doi/pdf/10.1111/mms.12170

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.