Rule of thumb is the smaller the animal, the faster the heart rate. A healthy adult human at rest has about 60 heartbeats/min. Young babies can be double that. Elephants' hearts probably only beat a few times a minute whereas mice are off the scale!
Another rule of thumb is that (apart from humans) each animal (I presume this only applies to the main mammaly type things) has 800 million heartbeats per lifetime. So e.g. dog = 15 years = 450 million seconds = 2 per second; mouse = 2 years = 60 million seconds = 12 beats per second; elephant = 70 years = 2200 million seconds = 1 beat per 3 seconds etc.
I like that bernardo.
It does work for humans if you work on the premis that we are only meant to live about thirty years (were it not for modern living and medical care).