Jessie Gibb, of Ardgowan School, asks :-

Why don't cats and dogs live to 100 like humans?

Alex Davies, a vet at Massey University, responded.

If we look at animals with a wide range of body size, such as mice to elephants and whales, we find that small animals don't live long. A mouse lives for only about two years and a cow about 30 years.

There are plenty of exceptions: humans live remarkably long for their size. But it is generally true that small animals eat a lot more in proportion to their body size, almost their own weight in food per day, they breathe faster and they have a higher heart rate. They wear out faster. For all the difference in how long they live, the hearts of mammals (the warm-blooded, furry animals) beat about the same number of times (500 million) before they die.

So our pet cats and dogs grow up, become old, and die within just a small part of our lives. Because they are close members of our families, this can bring much sadness. Do you think this is a disadvantage, or an advantage, in keeping a cat or dog?