Fur seals do, but sea lions don’t – cross taxa insights into exhalation during ascent from dives

Sascha Kate Hooker*, Russel Andrews, John Arnould, Marthan Bester, Randall Davis, Stephen Insley, Nick Gales, Simon Goldsworthy, Chris McKnight

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
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Management of gases during diving is not well understood across marine mammal species. Prior to diving, phocid (true) seals generally exhale, a behaviour thought to assist with the prevention of decompression sickness. Otariid seals (fur seals and sea lions) have a greater reliance on their lung oxygen stores, and inhale prior to diving. One otariid, the Antarctic fur seal (Arctocephalus gazella), then exhales during the final 50–85% of the return to the surface, which may prevent another gas management issue: shallow-water blackout. Here, we compare data collected from animal-attached tags (video cameras, hydrophones and conductivity sensors) deployed on a suite of otariid seal species to examine the ubiquity of ascent exhalations for this group. We find evidence for ascent exhalations across four fur seal species, but that such exhalations are absent for three sea lion species. Fur seals and sea lions are no longer genetically separated into distinct subfamilies, but are morphologically distinguished by the thick underfur layer of fur seals. Together with their smaller size and energetic dives, we suggest their air-filled fur might underlie the need to perform these exhalations, although whether to reduce buoyancy and ascent speed, for the avoidance of shallow-water blackout or to prevent other cardiovascular management issues in their diving remains unclear.
Original languageEnglish
Article number20200219
Number of pages11
JournalPhilosophical Transactions of the Royal Society. B, Biological Sciences
Issue number1830
Early online date14 Jun 2021
Publication statusPublished - 2 Aug 2021


  • Otariid
  • Fur seal
  • Sea lion
  • Diving
  • Physiology
  • Gas management
  • Shallow-water blackout


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