Why do stray cats in Singapore have half-tails or kinked-tails?

When we first saw these cats, our family thought some sadistic people were mutilating the stray cats of Singapore.  The length of the chopped off tails seemed random as did the kinks. 

I found many other people on the web commenting on the same thing:
- ”I used to think all these wretched cats were getting their tails trapped in car doors (ouch!)”
- “When we first arrived we thought the Chinese went around with cleavers chopping the tails off!!”

According to the Singapore SPCA, it is a common trait amongst Singapore cats. They are born that way.  Cats in Singapore belong to the bobtailed cat family.  They originated from the Japanese Bobtail cat which interbred with the local feral cats.

Claire Neckar, a zoologist who noticed the preponderance of kinky-tailed cats, said “the distorted tails point to their superiority over straight tails for a tropical climate, but what they can offer a cat in a hot climate that straight tails can't is anyone's guess."

There are a number of tales about Asian bobtailed cats. The most unusual is that a princess threaded her rings on a cat’s tail for safekeeping and the loyal cat wrapped its tail around the rings to keep them place.