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Top-level
Actually, I take that back, I can only read the abstract right now but this older academic review article suggests longer-diving mammals generally exhale. It's an older article though so the answer might be more complicated now. https://www.sciencedirect.com/science/article/abs/pii/0034568783900725 3 comments
Right, so, the general thinking is deep diving mammals spend a period at the surface engaging in gas exchange to replenish oxygen stores in tissues (and remove carbon dioxide). Then there isn't an advantage, and if anything, there's a disadvantage, to filling the lungs with air at the start of the dive. I think this detail has stuck with me because it's surprising compared to how humans typically dive. But we don't go very deep (without scuba gear!) and we don't have as dramatic of circulatory changes as the marine mammals do. |
Gregory's Server
@theantlady I found this. I think they take a breath in to super oxygenate the blood and muscles then compress the lungs to prevent gas exchange.
And I was wrong about the time they can be submerged during an active deep dive. More like 20 minutes to an hour in full activity mode.
https://www.scientificamerican.com/article/how-do-deep-diving-sea-cr/