Pulse Rate, Metabolism, Size... & more Hearty facts

A faster heart and a faster metabolism too!

Smaller animals use more energy for their body mass to maintain their body temperature

...because they lose heat faster than larger animals.

 Birds 

Mass (grams) 

Pulse Rate (beats/minute)

canary

pigeon 

crow 

buzzard

wild duck 

hen 

domestic duck 

turkey

 20 

300 

341 

 658 

1100 

2000 

 2300 

8750

1000 

185 

378 

300 

190 

312 

240 

193

The Heart of an ELEPHANT weighs between 40 and 60 pounds and beats about 30 times a minute.

Larger animals have larger hearts too, and they are connected to large veins and arteries. 

 

The large hearts can generate great pressures while pumping blood, and due to the sheer quantity, increasing the risk of harming the blood vessels.

It also takes longer for the pressure to push the blood to limbs 'far' away, and therefore increasing the pulse rate would not really serve its purpose.

Mammals

Mass (grams) 

Pulse Rate (beats/minute)

mouse 

rat 

guinea pig 

rabbit  

small dog 

large dog  

man 

horse 

25 

200 

300 

2000 

5000 

30000 

70000 

450000

670 

420 

300 

205 

120 

85 

72 

38

Why do smaller animals have faster heart rates?

Smaller animals are constantly on the lookout for danger and must be able to react quickly when they need to.

A fast heart and breathing rate ensures that enough oxygen is being put into the bloodstream to allow the animal to move quickly without getting tired, or eaten.

Also, because the animal is smaller, it doesn't take the blood very long to travel one loop around the circulatory system, as it might if it were an elephant or a whale.

The circulation is therefore quicker allowing the heart less time to relax in between pumps.