Locomotion in diving elephant seals: physical and physiological constraints

Area of Science:

• Marine Biology
• Animal Physiology
• Bioenergetics

Background:

• Elephant seals (Mirounga angustirostris) exhibit remarkable diving capabilities, utilizing negative buoyancy.
• Understanding energy conservation strategies is crucial for comprehending their prolonged dive durations and foraging success.

Purpose of the Study:

• To model the energetic costs associated with transit and foraging dives in elephant seals.
• To investigate the role of negative buoyancy and gliding descents in reducing metabolic rate and extending dive times.

Main Methods:

• A numerical integration technique was employed to model dive energetics.
• Simulations incorporated parameters such as swim speed, descent/ascent angles, and locomotion modes (stroking vs. gliding).
• Model inputs utilized realistic data from previous experimental studies on elephant seals.

Main Results:

• Gliding descents offered minimal energetic savings for transit dives compared to surface swimming.
• Variable energy savings were observed for foraging dives, with deep mid-water dives showing the greatest benefit (approx. 18%).
• Flat-bottom foraging dives at 400m showed reduced energetic advantages due to increased stroking.

Conclusions:

• Gliding descent can be an effective energy-saving strategy for elephant seals, particularly during deep mid-water foraging.
• Further research using advanced animal-borne instrumentation is needed to fully elucidate the benefits of gliding across different demographics and dive types.
• Factors beyond energetics, such as feeding and predator avoidance, may influence dive depth selection.