Which animal has the fastest heart beat?

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