Scientists follow 77 species for 60 years to try to reveal the secrets of a long life

By Mike Gardner, Flinders University

June 29, 2022

Have you ever wondered the secret to a long life? Perhaps understanding the lifespans of other backbone animals (or “vertebrates”) could help us unravel this mystery.

You’ve probably heard that turtles live long (and slow) lives. At 190, jonathan The Seychelles giant tortoise may be the oldest living land animal. But why do some animals live longer than others?

To research published last week by myself and my colleagues in the journal Science investigates the various factors that can affect longevity (lifespan) and aging 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 over 100 scientists with up to 60 years of data on animals that have been captured, tagged, released and recaptured.

This data was then compared with existing information on warm-blooded animals, and several different ideas about aging emerged.

Jonathan the tortoise lives on Saint Helena Island, a small isolated British colony west of Angola, Africa. Photo credit: Saint Helena Tourism Board/EPA

What factors might be important?

cold blood or hot blood

A popular line of thought that we have studied is the idea that cold-blooded animals like frogs, salamanders and reptiles live longer because they age more slowly.

These animals must rely on outside 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).

Small, warm-blooded animals, like mice, age quickly because they have faster metabolisms — and turtles age slowly because they have slower metabolisms. By this logic, cold-blooded animals should have lower metabolisms than warm-blooded ones of similar size.

However, we found that cold-blooded animals do not age more slowly than warm-blooded animals of similar size. In fact, the variation in aging among the reptiles and amphibians we examined was much larger than expected. Thus, the reasons why vertebrates age are more complex than this idea suggests.

Ambient temperature

Another related the theory is that the ambient temperature itself could be a factor in longevity. For example, animals in colder regions may process food more slowly and have periods of inactivity, such as hibernation, resulting in an overall increase in lifespan.

In this scenario, cold-blooded and warm-blooded animals from colder regions would live longer than animals from warmer regions.

We found this to be true for reptiles as a group, but not for amphibians. Importantly, this finding has implications for the effects of global warming, which could lead to more rapid aging of reptiles in ever warmer environments.

The small striped brown lizard sits on a rock
The viviparous lizard (Zootoca vivipara) is one of the cold-blooded species we studied. Photo credit: Shutterstock


A suggestion is that animals with certain types of protections, such as protruding spines, armor, venom, or carapaces, do not age as quickly and therefore live longer.

A lot of energy is invested in the production of these protections, which can allow animals to live longer by making them less vulnerable to predation. However, does the very fact of having these protections allow animals to age more slowly?

Our work has revealed this to be true. It seems that such protections allow animals to live longer. This is especially true for turtles, which have tough shells and incredibly long lifespans.

We will need to conduct more research to understand why simply having pads is linked to a longer life.

A crocodile sits on the bank of a river with its mouth open
A species of crocodile studied, Crocodylus johnsonihas a powerful armored body with protruding scales that protect it from predation. Photo credit: Shutterstock

the reproduction

Finally, he was laid that longevity is perhaps related to the end of an animal’s life to reproduce.

If they can continue to reproduce later in life, then natural selection will drive this ability, from generation to generation, allowing these animals to live longer than those that reproduce early and cannot continue to do so.

Indeed, we have found that animals that start producing offspring at a later age seem to live longer. Sleeping lizards (or shingles) are a prime example. They don’t breed until they are about five years old and live to be almost 50 years old!

The challenge of understanding aging

To understand aging, we need a lot of data from the same animals. It’s simply because if we want to know how long a species lives, we have to keep catching the same individuals over and over again, over long periods of time.

This is a “longitudinal” research. Fortunately, that’s exactly what some scientists are committed to. That’s also what my team does with sleeping lizards, Tiliqua rugosa. These lizards have been studied continuously at Bundey Bore Station in north central South Australia since 1982.

The sleeping lizard is one of the species used in the study of longevity. To our knowledge, this species lives up to 50 years. Photo credit: Mike Gardner

Here, more than 13,000 lizards have been captured in 40 years of study. Some have been caught up to 60 times! But given the 45-year longevity of these lizards, we’ve been studying them for less time than some of them live. By continuing the investigative work, we may find that they live even longer.

The risk of death for some animals is not related to age

Another interesting part of this research was finding, for a range of animals, that their risk of dying is just as low when they are old enough as when they are young. This “negligible aging” is found in at least one species each of frogs, salamanders, lizards, crocodiles and, of course, turtles like Jonathon.

We don’t really know why. The next challenge is to find out – perhaps by analyzing the genomes of species. Knowing that some animals have negligible aging, we can target these species for future investigations.

Understanding what leads to long life in other animals could lead to different biomedical targets to study humans as well. We may not live to be Jonathan the turtle, but we could theoretically use this knowledge to develop therapies that help stop part of the aging process within us.

For now, eating healthy and exercising remain safer ways to live longer.

This article is republished from The conversation under Creative Commons license.

Related: Hibernating animals find anti-aging cure

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