Comparison of marine mammals and humans

[fabrice]

Hello,

I'm looking for informations to do a presentation on the subject "why us mere humans are we so bad at freediving compared to marine mammals".
I'm not looking for an in-depth description of physiological mechanisms, but items like :
- some mammals don't have to equalize since their ears are filled with fluid.

Any info/pointers appreciated ! Thanks !

Fabrice

[Adrian]

Fabrice,
Do a search on mammals here. There's been quite some discussion by efattah and others on the subject, you'll find some interesting information.

Adrian

[DeepThought]

If I remember correct these 2 articles were very interesting:
http://www.deeperblue.net/article.php/316/%200/0
http://www.deeperblue.net/article.php/318/19/0

The second one is about penguins.

[sinkweight]

Good links, Deep

Maybe somebody can now explain why I'm mistaken for a new species of Beluga.

I could stand to lose a few pounds and maybe get some sun, but C'MON!

[Adrian]

It's very simple Warren, it's all in your accent! Everybody knows that belugas have a good Texan drawl Tell me, is your avatar a reflection of how you feel after a hangover?

Adrian

[efattah]

The simple answer:

1. Marine mammals have a FAR GREATER oxygen storage capacity, in terms of oxygen per unit body mass, mostly due to higher blood volume per unit body mass, and higher oxygen storage in their muscles (in the form of myoglobin). Their muscles have ten times more myoglobin than humans.

2. Far more streamlined body shape allows for effortless movement through the water. Humans have a non-streamlined shape which makes swimming full of effort, wasting oxygen.

3. Marine mammals are nearly neutrally buoyant, reducing the effort to get down.

4. The blood vessels in their eustachian tubes swell with blood, meaning they don't need to equalize their ears.

5. They have a profound oxygen conserving diving reflex once they start the dive. Their heart rate slows dramatically, and blood is shifted away from non-essential muscles & organs, reducing the oxygen consumption of non-essential functions. For example, blood flow to the stomach is completely stopped during a dive. In a human, the stomach will continue digesting and burning oxygen during a dive (although the effect is diminished in expert divers).

6. The deepest diving mammals exhale before they dive, so they don't bring down too much nitrogen, and thus avoid decompression sickness and narcosis.

7. Marine mammals can withstand far greater amounts of CO2, and far lower levels of oxygen. At the level of oxygen which would cause unconsciousness in a human, a marine mammal's brain is still working fine, with clear thinking and quick reflexes.

[Bill]

There's another very important difference, sometimes overlooked. Marine mammals 'train' every day.
Aloha
Bill

[sinkweight]

It's very simple Warren, it's all in your accent! Everybody knows that belugas have a good Texan drawl

Well, looking from my picture, I'm starting to see the resemblance!

as for my current avatar...it's off of a 70's childrens show called Sigmund and the Sea Monsters...the picture being of Sigmund Ooze, the main character. A crappy costume, manned by small person extraordinnaire, Billy Barty. It was part of a Sid and Marty Croft weekly special here in the states. Psychadelic morning bonanza for kids two warp their impressionable minds around on Saturdays.

I'm definitely one of the deeper-scarred kids.