• Question: How come rabbits jump around all day and eat carrots but only live 16 years. Whales swim around all day and only eat fish but are fat. Turtles just sit around all day yet live for a hundred years. Why?

    Asked by alanah to Michael on 11 Nov 2013.
    • Photo: Michael Nolan

      Michael Nolan answered on 11 Nov 2013:

      Hi Alanah,

      good question – here is my hypothesis…
      It is probably based on factors that determine aging in animals. You will notice that the most active of the animals in your list live the shortest while the slowest/least active live longest. Humans are probably in the middle.

      If we remove external factors (that is things like predators, weather, anything outside of the animal’s control that could harm them) and consider the animals, it is likely that that very slow metabolisms of turtles contributes to their surviving longer.

      They take longer to grow and are less active. The last point means that the strain on their heart, skeleton etc is much smaller, which means the heart, skeleton etc do not deteriorate as quickly as in a rabitt which with all its activity is putting the heart, skeleton under strain and so they live for a shorter time.

      Another factor could be evolution. Rabbits have lots of babies very quickly, turtles are the opposite. Evolution wants the genes of an animal to be passed to the next generation, so for that to happen to a turtle, you need to give lots of time for mating to happen. So if the turtle lives longer, it has more chances to mate and pass on its genes. since the rabbit has a short lifespan, it needs to mate and have offspring early and lots of them.

      This is a really good question, which scientists are trying to figure out, so well done. There is lots of work on understanding aging in animals and humans.

      M

Comments

  • Photo: Sive

    Sive commented on :

    Great question Alanah and cool answer Michael,
    There seems to be a general trend for longevity to scale with body size; so larger animals tend to live longer. But sometimes these patterns don’t necessarily follow each other. For example, bats live far longer than expected for their body size. One of the ideas people have proposed to explain why there is such variation in the lifespan and rate of aging of birds and mammals is the extrinsic mortality hypothesis. This is just a fancy way of saying that animals which are exposed to a high risk of death from external factors such as predators or competitors are more likely to have a “live fast, die young” mode of life like the rabbits. It comes back to what Michael was saying about evolution being all about passing on your genes to another generation. If you’re likely to get eaten by a fox relatively early in life, it makes sense to mature quickly, have lots of babies and then, evolutionarily speaking, it doesn’t matter as much if you die once you have passed on your genes to the next generation. On the other hand, once whales are fully grown they’re unlikely to die of extrinsic causes (i.e. things other than old age) and so they can “afford” to take their time reaching maturity and invest lots of energy in just producing a few offspring.
    We did a group project recently which looked at the ecological factors that seem to correlate with relatively longer life spans in mammals and birds. There seems to be a pattern that, for a given body size, animals who have ways of escaping predators (by flying, digging or taking to water) seem to live longer than their close relatives who don’t have these escape methods.

    • Photo: Michael

      Michael commented on :

      Nice answer Sive: I think mine was a bit too physical scientist 🙂
      On your last paragraph, you exclude reptiles, since turtles might not fit the hypothesis you explore? Scuse my ignorance if I miss anything!

      • Photo: Sive

        Sive commented on :

        For that paper we left out reptiles for two main reasons. They’re ectotherms with very different growth rate patterns to mammals and birds so it’s tricky to make direct comparisons. Also, the longevity data that’s available for birds and mammals is far better than the data that’s out there for reptiles!

        • Photo: Michael

          Michael commented on :

          So, this question may not have a general answer – you have to break the animal kingdom into pieces and look at each piece?
          Do you think we will unlock any secrets to aging and how to combat it, or will the simple physics of bone, tissue and muscle simply be unbratable?

  • Photo: ladybird117

    ladybird117 commented on :

    can dogs see in black and white or colored

    • Photo: Sive

      Sive commented on :

      Hi ladybird 🙂

      Colour vision is all to do with the coloured light receptors we have in our eyes called cones. Humans have 3 types of cones which we use in combination to distinguish different colours. Dogs only have two types of cones so they can see some colours but not as many as we can. They have cones that allow them to distinguish between blue and yellow light but they can’t tell the difference between red and green. Some people think that red and green objects appear grey to dogs while other research has found evidence that dogs might see red and green objects as different shades of blue or yellow. It’s hard to be certain because we can’t really ask the dogs!
      Sive

  • Photo: alanah

    alanah commented on :

    Thank you for your answers I think I understand now 🙂

  • Photo: zebraperson72

    zebraperson72 commented on :

    I have always wondered that, now I know ! 🙂

  • michaela commented on :

    why do we laugh