Published: November 2, 2022
Ever wondered about the secret to a long life? Perhaps understanding the lifespans of other animals with backbones (or “vertebrates”) might help us unlock this mystery.
You’ve probably heard turtles live a long (and slow) life. At 190 years, Jonathan the Seychelles giant tortoise might be the oldest land animal alive. But why do some animals live longer than others?
Research published today by myself and colleagues in the journal Science investigates the various factors that may affect longevity (lifespan) and ageing in reptiles and amphibians.
We used long-term data from 77 different species of reptiles and amphibians – all cold-blooded animals. Our work is a collaboration between more than 100 scientists with up to 60 years of data on animals that were caught, marked, released and re-caught.
These data were then compared to existing information on warm-blooded animals, and several different ideas about ageing emerged.
One popular line of thought we investigated is the idea that cold-blooded animals such as frogs, salamanders and reptiles live longer because they age more slowly.
These animals have to rely on external temperatures to help regulate their body temperature. As a result they have slower “metabolisms” (the rate at which they convert what they eat and drink into energy).
Animals that are small and warm-blooded, such as mice, age quickly since they have faster metabolisms – and turtles age slowly since they have slower metabolisms. By this logic, cold-blooded animals should have lower metabolisms than similar-sized warm-blooded ones.
However, we found cold-blooded animals don’t age more slowly than similar-sized warm-blooded ones. In fact, the variation in ageing in the reptiles and amphibians we looked at was much greater than previously predicted. So the reasons vertebrates age are more complex than this idea sets out.
Another related theory is that environmental temperature itself could be a driver for longevity. For instance, animals in colder areas might be processing food more slowly and have periods of inactivity, such as with hibernation – leading to an overall increase in lifespan.
Under this scenario, both cold and warm-blooded animals in colder areas would live longer than animals in warmer areas.
We found this was true for reptiles as a group, but not for amphibians. Importantly, this finding has implications for the effects of global warming, which might lead to reptiles ageing faster in permanently warmer environments.
One suggestion is that animals with certain types of protections, such as protruding spines, armour, venom or shells, also don’t age as fast and therefore live longer.
A lot of energy is put into producing these protections, which can allow animals to live longer by making them less vulnerable to predation. However, could it be the very fact of having these protections allows animals to age more slowly?
Our work found this to be true. It seems having such protections does lead to animals living longer. This is especially true for turtles, which have hard shell protection and incredibly long lifespans.
We’ll need to conduct more research to figure out why just having protections is linked to a longer life.