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How long do crocodiles live for?

The answer to this question is difficult to answer precisely and, like the size of crocodiles, suffers from exaggeration. There are a few clues, however, which can tell us the age of these venerable reptiles. Did you know the oldest crocodile reportedly died in 1997 at a zoo in Russia, aged 115 years old? I have not been able to verify this story entirely, but there's good evidence to suggest that it is true (the crocodile was originally captured in the 1890's as a 5 to 10 year old juvenile).

Gomek Measuring the longevity of crocodiles can be very difficult, because they live for such a long time. Reliable age records are more difficult to come by, and typically derive from captive animals which has problems (see below). The image on the left is Gomek, who died in February 1997 at the St. Augustine Alligator Farm. He was 17.9 feet when he died, and around 70 to 80 years old. He was captured in Papua New Guinea as an adult, and his age at that time was unknown, although he grew less than a foot in the 20 years he remained in Florida.

How is age measured? There is currently no reliable way of measuring crocodile age, although several techniques can be 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. This is problematic for animals living in tropical climates (ie. most species) as growth rates within a year vary much less than those in temperate climates where there are distinct seasons. Innermost growth rings also degenerate over time, and most measures of age using growth ring data will underestimate age. A more reliable method is to mark a young animal of known age and determine age whenever it is recaptured. Unfortunately this technique takes the animal's entire lifetime to come up with a figure! Even then you rarely know whether an animal died or moved out of the area, and whether it died of natural causes or was killed. A 22 year study on Australian freshwater crocodiles has revealed good evidence of animals at least 50 to 60 years of age, estimated from recaptures dating back to the late 1970s, and extrapolated from growth rates. This is fairly typical for most medium-sized species.

Estimating maximum age from animals which have lived and died in captivity is problematic as we don't know whether the animal lived as long as it would under natural conditions - or longer than a wild animal! Stress, incorrect diet, disease - all these can cause premature death in captivity, although factors such as predation are usually eliminated. It is possible that mean age in captive animals is higher than in wild populations, but that maximum age is achieved in animals in the wild (where conditions may be optimal, assuming the animal survives to such an old age).

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, and there is limited evidence that some individuals may exceed 100 years. Certainly, individuals in many aboriginal tribes recognise very old crocodiles that have been alive for as long as they can remember. The same is true of C. niloticus, which probably lives nearly as long as the saltwater crocodile. One of the oldest crocodiles recorded died in a zoo in Russia apparently aged 115 years old. Unfortunately, the news report did not identify the species.
 
Sweetheart
   SWEETHEART AFTER CAPTURE

Sweetheart, a large saltwater crocodile from Australia, was captured from a lagoon after terrorising fishermen - or, more specifically, their boats. He gained a reputation for attacking outboard motors (probably because of the low-frequency vibrations they emitted, or because of their shape). He never attacked a person. However, it was decided to move him before a fatality occurred. Unfortunately, like many large and old crocodiles, the stress of capture was too much for him and he died.

Other species may not live as long, especially members of the family Alligatorinae. Caimans are estimated to live only 30 to 40 years, for example. Such ages are likely to be underestimates, having come from zoo animals. It is clear that stories of crocodiles living hundreds of years are simply untrue, yet there is reasonable evidence that medium to large species are capable of attaining at least 60 to 70 years when disease, starvation and predation have been avoided.

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