According to this article, rats could grow to be the size of sheep.
http://au.news.yahoo.com/world/a/21250849/huge-rats-could-evolve-scientists-claim/
The argument is that as other, larger species become extinct, the rats will take advantage of the job opening and grow to fill it. I suspect that this article will be quite alarming to some, but when you think of it – Why?
What makes rats creepy? They live in dark, dank places like sewers and basements and rubbish bins. But if they were the size of sheep, that would no longer be possible. They would have to move above ground or risk plugging up the works.
There are already rodents as big as sheep. The Capybara is native to South America and are pretty darned cute (I took this pic off the internet from a Huffington Post article).
I mean come on. It’s so cute it hurts.
Another large rodent that is near and dear to my own heart is the noble and majestic beaver.
Who could be afraid of this??? Clearly sweet and god fearing and praying… (Picture also lifted from the ever giving internet).
I suppose the biggest downside would be their unsuitability for laboratory studies. We’d have to use hedge mazes to test them. Although, we already have giant hamster balls for them to play in (currently being used by people with hamster sized brains, again, picture totally pilfered off the net).
But since animal testing is growing less and less acceptable, this drawback is unlikely to be an issue by the time ratsheep arrive.
So, people of the earth, fear not the rodents of unusual size. Unlike most animals, they seem to get cuter as they get bigger.
The Shrinking Head 