Why can most 4-legged land animals swim?

Factual Questions
1

I am helping my daughter with her science project. So, so asked the question why can most 4-legged land animals “swim”? Makes you go humm! Does anyone know the answer?

Thanks in advance for your help.

2

I believe it’s b/c

  1. the trunks of most animals’ bodies are buoyant (ours included)

  2. The position of the head/neck allows for the head to remain above water while the animal floats (unlike us–which is why we have so much trouble)

  3. the leg motions they use to propel themselves on land are easily translated to propelling them in water (i.e., they just “walk” in the water, whereas our walking method is totally unsuited for swimming)

3

I was just reading an article that may be germane to your question. It detailed the thinking of this obscure 19th century British scientist, Charles something, I think.

Anyway, I had never heard of the guy. But apparently, he proposed that the traits we see in living creatures today have their origins far in the past. And that traits aren’t static; good traits are preserved whereas maladaptive traits are lost. His disciples (a real clandestine group) maintain that all the complexity of modern life arose from simple beginnings, presumably by this process of modification an selection.

They also maintain that life arose in the oceans, and only later developed the traits required to survive on land. Therein may be the clue: we swim because our ancestors swam. Our physiology was well adapted to an aquatic lifestyle in the past, and for most creatures, the demands imposed for landlubbing, haven’t modified our original anatomy or neurophysiology to an extent that we can no longer swim. Not to mention that swimming actually helps some animals survive.

I still can’t think of the name of that Charles guy. Can anyone help me out?

4

The simplest answer is that there’s no particular reason for them not to be able to swim. As toadspittle said, as long as an animal can float (given body composition, most can), keep its head out of the water (and for most mammals, this is a fairly natural position), and move its legs, it will ‘swim’ after a fashion, although not necessarily very well. And if the ability allows them to avoid drowning in a flood or cross a river to new habitat even ocassionally, there is no reason for the ability to be lost.

The general topic of animals swimming received a lot of discussion in the Staff Report Is the camel the only animal that cannot swim? and the follow up thread:

http://boards.straightdope.com/sdmb/showthread.php?threadid=41778

The discussion showed that, rather surprisingly, the only mammals for which there is good evidence that they cannot swim are the apes (Gorilla, Orangutan, Chimp, and gibbons). There are some assertions that giraffes and perhaps some gophers can’t swim, but it didn’t seem to be definitely established. However, a lot of really outlandish mammals are known to be able to swim: kangaroos, moles, sloths, armadillos, elephants, bats, etc.

And choosybegger, I don’t have the slightest idea who you might be thinking of. Can you give us a few more hints?