South American opossums age extremely rapidly, exhibiting cataracts and muscle loss by 18 months of age.

“you know so this is an animal the south american ones that we're studying look very much like the north american opossums most people would not be able to tell the difference um so they're about the size of a small cat and i expected they would live 10 or 20 years like cats do and here at 18 months they would get cataracts they would lose muscle they would be able to parasitize they would just look terrible even the same animal that i'd caught three months earlier and i just became incredibly intrigued with why they would age so much more quickly than it than a cat”