• Question: Do big animals or small animals have a longer life expectancy?

    Asked by amybyrne to Aggelos, Andrew, Eileen, Naomi, Shane on 13 Nov 2012.
    • Photo: Andrew Jackson

      Andrew Jackson answered on 13 Nov 2012:

      hi amybyrne

      generally big animals live longer than small ones. We think this is becuase small animals tend to have hearts that need to beat faster to keep them alive than big ones – the reasons for this are due to the way big animals use energy more efficiently than small ones.

      There are some really interesting animals though that live far longer than you would expect for their size. Bats, naked mole rats (http://en.wikipedia.org/wiki/Naked_mole_rat) and parrots all live far longer than other animals of a similar size. One explanation is that animals that live in social groups, tend to live longer (including humans, monkeys and apes) because they can help and assist each other, but also becuase these social animals tend to be more intelligent and so can in theory use their environment more efficiently than less intelligent animals that live on their own.

    • Photo: Eileen Diskin

      Eileen Diskin answered on 15 Nov 2012:

      Like Andrew says, there are some exceptions – but its usually the big animals that live longer.

      And generally, there are fewer of the big animals then there are of the small ones. Like ants, for example: except for the queen they generally dont live very long at all. But ants have LOTS of babies – thousands! Compare this to humans, which are a lot bigger – and usually a mother only has a few babies.

      So intersestingly – the total weight of all of the ants on Earth at any time is equal to the weight of all of the humans! (And humans live a lot longer to see tons of ant generations :))

    • Photo: Naomi Elster

      Naomi Elster answered on 17 Nov 2012:

      Generally it is because larger animals, as Andrew says, live in social groups and use energy less efficiently. Some large animals, if attacked, will actually arrange themselves in a circle, with the old and very young inside the circle and the strong adults standing in a ring around them to defend them. Larger animals also tend to have much fewer babies and to nurture their babies – the longer an animal has until it reaches adulthood, the more time it has to learn from its parents, and this learning can be crucial to its survival. Big animals are also likely to be much better fed and cared for when they are young and will only become independent from their mothers when they are strong enough to. Also, the fact that there are fewer of them means there will be less competition for food, safe shelter, and their other needs.

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