For instance, the capybara, a giant amphibious guinea pig the size of a labrador.
Early Spanish invaders of South America had trouble finding enough plant food to let them observe the Catholic tradition of meat abstinence during Lent.
They got round the problem by getting the Vatican to decree that because the capybara is amphibious it therefore counts as fish.
Next mad animal? Thanks to a piece in The Independent, I learn of the markhor. It's a goat that stands 6 foot tall, with spectacular twirly corkscrew horns adding another couple of feet.
[piece reproduced in full cos The Independent have a habit of doing pay-archiving]
Giant goat survives war zone
The ceasefire between India and Pakistan in Kashmir has produced an unexpected beneficiary - the world's largest goat.
The markhor, a mountain goat that stands almost 6ft tall at the shoulder and can weigh 17 stone, was thought to be extinct in Indian-held Kashmir. But a recent joint survey by Indian wildlife organisations and the Indian army found 35 small herds - 155 goats - thriving near the Line of Control.
As recently as 1970 there were 25,000 on the Indian side, but by 1997 they had been driven to near extinction. The main cause was the conflict. But markhor are also hunted for their spiral horns - a mounted pair can sell for £850. The horns are also used for Chinese medicine; a kilogram fetches £600 in China.
Markhor are considered critically endangered, but other populations have survived in the mountains of Pakistan away from the Line of Control, and in Afghanistan and Turkmenistan.
In the same mad way that South Americans can't do the decent thing and leave the 'fish' capybara alone, Pakistan still legally permits markhor hunting despite their status as a critically endangered species. Fuckers. If I were in charge of goats that good I'd just fuss them all day long.
Personally I think the problems of Kashmir could be resolved by telling both India and Pakistan to fuck off out of it and declaring the territory an independent goat republic. With six foot goats armed with big horns, you'd not mess with the border patrols.