World's largest captive croc turns 120, giving scientists 'serious knowledge on longevity'

Scientists think that Cassius, a nearly 18-foot-long saltwater crocodile living in captivity, is roughly 120 years old. (Image credit: Marineland Melanesia Crocodile Habitat)

Cassius, the world's largest crocodile living in captivity, just turned 120 years old. Or at least that's his estimated age, scientists say. 

It's difficult to determine a crocodile's age based on its size. Once they reach adulthood, the rate at which crocodiles grow slows down and eventually grinds to a halt. The largest crocodiles are usually the ones that grow in irregular spurts as juveniles, with males typically growing bigger than females.