Their heartbeat?

Question

i heard that the heartbeat of animals increase the smaller they are.is it true?

Answer 1

Yes.

The relationship between body size and heartbeat rate for a mammal is:

Heartbeat rate (beats per minute) = 241 / fourth root of Body weight (kg)

So according to this formula, if the body weight is 81 kg, the heartbeat should be 241 divided by 3, roughly 80 beats per minute. For different classes of animals, like the reptiles, amphibians and such, this relationship will not necessarily hold, because of metabolic differences. Also, remember the heartbeat rate is heavily affected by other factors such as exertion, nervousness, body chemistry, or species specialization.

http://www.hhmi.org/biointeractive/heart...

Answer 2

I believe so; I remember I did a bio lab looking at Daphnia, which are tiny animals that live in ponds.  Looking at them through the microscope, you can actually see them very well, and their hearts were going crazy just sitting around.

However, I don't know if this consistent across all animal spectra (though I also can think of some vague anecdotal stuff) or why this would be.