Why can some animals hold their breath for a really long time? I.e., turtles, dolphins, whales, etc… Do they have really big lungs for their size? Do they store oxygen in places other than their lungs? Do they have lower oxygen needs than humans? Are they just more efficient at using oxygen?

Question

Why can some animals hold their breath for a really long time? I.e., turtles, dolphins, whales, etc… Do they have really big lungs for their size? Do they store oxygen in places other than their lungs? Do they have lower oxygen needs than humans? Are they just more efficient at using oxygen?

In: 8

Answer 1

All of the above!

Specifically for dolphins and whales as that’s my area of expertise but similar adaptations can be found in other marine mammals:

– large lung volume allows for one big breath filled with as much oxygen as possible

– modified lung surfactant (substance that costs the inside of the lungs) allows for almost complete collapse of the lungs when at depth. This helps force the gas inside the lungs to be absorbed into the blood, making it available for the body

– flexible ribs help with lung collapse

– more oxygen-binging molecules in blood but more importantly in muscles. You know how chicken meat is rather pale compared to beef? Dolphin nest is several shades darker still, almost dark brown. This is due to more myoglobin, a molecule that binds oxygen in the muscles. This means that once oxygen is stored in the muscle, no transport from the lungs is required, therefore no breath, allowing for deeper and longer dives until the myoglobin stocks run out

– selective shunting of the blood away from irrelevant organs. While on a deep dive, it’s unnecessary for the dolphin to waste energy on digesting food for example, it’s better to use it for hunting or swimming. Therefore blood flow to the stomach is limited, allowing for the precious oxygen and nutrients to be available for the muscles.

– higher breath exchange volume. When we humans breathe through one cycle (inhale-exhale), we only exchange about 10-15% of the air in our lungs. That’s fine for us as we live in an environment where there is plenty of air. Dolphins can exchange as much as 95% of their lung volume which means they don’t have to spend much time at the surface before they are ready for the next five, and can recover from a dive much faster than we do