Factors affecting stroking patterns and body angle in diving Weddell seals under natural conditions

• Published in: Journal of Experimental Biology
• Main Authors: Sato, Katsufumi, Mitani, Yoko, Cameron, Michael F., Siniff, Donald B., Naito, Yasuhiko
• Format: Text
• Language: English
• Published: Company of Biologists 2003
• Subjects: Research Article; McMurdo Sound; Weddell; Antarc*; Antarctica; Weddell Seals
• Online Access: http://jeb.biologists.org/cgi/content/short/206/9/1461; https://doi.org/10.1242/jeb.00265

Aquatic animals use a variety of strategies to reduce the energetic cost of locomotion. Efficient locomotion is particularly important for breath-holding divers because high levels of exercise may quickly deplete oxygen reserves, leading to the termination of a dive. We investigated the swimming behavior of eight adult Weddell seals, which are proficient divers, in McMurdo Sound, Antarctica. A newly developed data logger was attached to free-ranging females at their own breeding sites to record swimming speed, depth, two-dimensional accelerations (stroke frequency and body angle) and temperature. All seals conducted multiple deep dives (the mean dive depth range for each animal was 223.3±66.5–297.9±164.7 m). Prolonged gliding while descending was observed with thinner females ( N =5 seals). But the fatter females ( N =3 seals) exhibited only swim-and-glide swimming, characterized by intermittent stroking and fluctuating swim speed, throughout their descent and ascent. The body angles of four of the seals were restricted to less than 30° by the location of breathing holes in the ice and the slope of local bathymetric features. Of these four, the three fatter seals adopted the stroke-and-glide method while the other thinner seal descended with prolonged periods of gliding. Prolonged gliding seems to be a more efficient method for locomotion because the surface time between dives of gliding seals was significantly less than that of stroking animals, despite their same stroke frequencies.