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I was watching a talk by Michio Kaku and he mentioned that crocodiles (or possibly alligators, I forget offhand) don't actually age -- they can die, but they essentially go through no aging process beyond adulthood

Can anyone link me any sort of detailed information on this?

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Well, this needs to be broken down into two parts. Do Crocodilians age (undergo senescence), and are Crocodilians immortal (will only die of external causes)?

Are Crocodilians immortal? - No. They appear to live about as long as humans before they die.

Measuring crocodile age is unreliable, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth—each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons. Bearing these inaccuracies in mind, the oldest crocodilians appear to be the largest species. C. porosus is estimated to live around 70 years on average, with limited evidence of some individuals exceeding 100 years. One of the oldest crocodiles recorded died in a zoo in Russia. A male freshwater crocodile at the Australia Zoo is estimated to be 130 years old. He was rescued from the wild by Bob Irwin and Steve Irwin after being shot twice by hunters. As a result of the shootings, this crocodile (known affectionately as "Mr. Freshy") has lost his right eye.

Do Crocodilians undergo senescence (show signs of aging)? Well, if this study from "Gerontology" written by Patnaik BK in 1994 is to believed... Maybe not.

Evidences and mechanisms of rapid or negligible senescence in reptiles are still fragmentary and unclear... neither the increase in mortality rate and accumulation of lipofuscin nor the reproductive senility have been shown conclusively in ageing reptile populations.

So, while Crocodiles and Alligators (both Crocodilians) definitely have a finite lifespan, because they just continue to grow it's hard to tell how long they have left until the day they die.

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  • $\begingroup$ Good answer, but I strongly disagree with the definition of immortal as "will only die of external cause". Immortal means that it does not die, whatever the cause. If they only died of extrenal causes it would just mean they they could not die of old age. $\endgroup$
    – nico
    Commented Nov 12, 2012 at 17:12
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    $\begingroup$ @nico - Which is precisely why I defined it in my answer. Talk to any Highlander fans, and Immortal means you can only die by having your head cut off - which also differs from your definition. :) $\endgroup$
    – MCM
    Commented Nov 12, 2012 at 17:39
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    $\begingroup$ Similarly in Tolkein, elves are immortal but can die in battle or from heartbreak. Both uses of "immortal" are common, and so MCM did the right thing by clarifying which way he was using it. $\endgroup$
    – Noah Snyder
    Commented Nov 13, 2012 at 20:26
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    $\begingroup$ @Good Gravy: [un]fortunately in biology definitions are extremely important. In any case let's stick to the question, which states that they die, i.e. they are not immortal. The question is whether they do not age which is a completely different thing biologically speaking. For instance, do crocodiles show signs of cellular aging, like telomeres shortening? Sorry but if we want to talk about elves or Highlanders I am very happy to do it, just not on a biology Q&A site. As I said before, I have nothing against MCM answer, just pointing out that the term immortal is misplaced here. $\endgroup$
    – nico
    Commented Aug 1, 2013 at 7:04
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    $\begingroup$ Other than external causes, what are the causes for a crocodile to die? Does an increase of aging increase the chances of organ failure? $\endgroup$
    – brillout
    Commented Nov 30, 2013 at 21:55

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