Module 2
Elephant Seal Deep Diving
Mirounga angustirostris (northern elephant seal) holds the mammalian depth record: 1 735 m, Robinson 2012. The species spends ~95% of its at-sea time submerged, cycling 20–25 min dives with 3–5 min surface intervals for months at a time. This module covers the deep-diving physiology and the neutral-buoyancy exploitation that makes it energetically possible.
1. Deep-Dive Kinematics
Le Boeuf 1988 and subsequent satellite-telemetry work catalogued continuous-diving patterns in both sexes. Typical mean depth 400–800 m, with individual dives exceeding 1 500 m in foraging seals pursuing mesopelagic squid and fish. Descent rate ~1 m s-1, ascent slightly slower; 90–95% of total time at sea is spent below 200 m.
2. Lung Collapse & Barotrauma Avoidance
As pressure rises with depth, lung air compresses; by ~150 m the alveoli collapse entirely, forcing remaining air into the cartilage-reinforced trachea and bronchi. This prevents nitrogen absorption at depth and eliminates decompression- sickness risk on ascent. Blood and muscle O2 stores (M1) supply metabolism throughout the dive.
3. Neutral Buoyancy Exploitation
After lung collapse the seal becomes essentially neutrally buoyant — subcutaneous blubber keeps positive buoyancy close to zero at working depths. Descent becomes a passive glide with flipper strokes only to steer; upward swim requires more active propulsion because the blubber becomes negatively buoyant near the surface. This asymmetry — glide down, swim up — is the core energetic trick that makes continuous diving affordable.
Simulation: Dive Profile & Buoyancy
Click Run to execute the Python code
Code will be executed with Python 3 on the server
4. Oceanographic Sampling
CTD-instrumented elephant seals are now a core component of Southern Ocean oceanography. Instruments glued to the hair deliver temperature, salinity, and depth profiles for months before moulting releases them. SEaOS (Seal-borne Ocean-Surveyor) has contributed more Southern Ocean profiles than any research vessel since 2004 (Roquet 2013).
Key References
• Le Boeuf, B. J. et al. (1988). “Continuous, deep diving in female northern elephant seals.” Can. J. Zool., 66, 446–458.
• Robinson, P. W. et al. (2012). “Foraging behavior and success of a mesopelagic predator in the northeast Pacific.” PLOS ONE, 7, e36728.
• Kooyman, G. L. & Ponganis, P. J. (1998). “The physiological basis of diving to depth: birds and mammals.” Annu. Rev. Physiol., 60, 19–32.
• Roquet, F. et al. (2013). “Estimates of the Southern Ocean general circulation improved by animal-borne instruments.” Geophys. Res. Lett., 40, 6176–6180.