Which animal has the fastest heart beat?

Answer 1

In general, the larger the animal is, the slower is its resting heart rate. Great whales (the

largest animals) have resting heart rates around 7 beats per minute (bpm), according to

Gordon Ramel (http://www.earthlife.net/mammals/blood.html), who also notes that some

smaller animals have even lower heart rates while hibernating (for example, the European

hedgehog, which slows from 200-280 bpm while active to around 5 bpm while hibernating).

(It's a good bet that there is some other animal with an even slower hibernating heart rate --

you might want to research this question a bit more).

Cold-blooded animals slow their hearts dramatically at low temperatures. At

http://www.peteducation.com/article.cfm?cls=17&cat=1848&articleid=295

you can read about how crocodiles, for example, slow their hearts from 24-40 bpm

in daytime (28C) to 15-20 bpm at night (18C), and to as slow as 1 bpm at 10C (which

is pretty cold for a croc).

At the other extreme, shrews have an average heart rate of 800 bpm and a peak rate

over 1300 bpm.

George Moody

Harvard-MIT Division of Health Sciences and Technology

Answer 2

the humming bird