Wearing fur in the tropics

I was watching David Attenborough's Wild Singapore the other night and was surprised to learn about its (now) locally famous family of otters living in Marina Bay, right in the city.   

I had no idea that otters even lived in a warm climate.  Their fur always made me assume they were cold water creatures only.  But obviously I was wrong. In fact:

Otters are found on every single continent in the world except for Australia and Antarctica. They enjoy the freshwater but they are also known to live in the saltwater of the oceans as well.

There's even a species of otter to be found in the middle of Africa.

How did Australia manage to miss out on them??  Was there some ancient territorial war with platypus that our poison spurred local river inhabitant won?

Anyway, this site explains that the Singaporean otters were no where to be seen in the 1970's, but they've reappeared since the city cleaned up its waterways.

Another site says that if you count all of the know otter families around the island, there are perhaps 50 furry residents. 

The things you learn...