The Colour of the Bear

One of my favourite mathematical riddles:

An explorer travelled 5 km South from his camp, then 5 km East, then 5 km North. He found himself back in his camp and saw a bear rummaging through his food supplies. What is the colour of the bear?

Don't cheat! Answer is below -- you need to highlight it to see.

The explorer's path forms an equilateral triangle with all the angles equal to 90°. Obviously we cannot assume a Euclidean plane here, but curved plane like our very Earth. The only possible situation for the stipulated directions and path is when the camp is exactly at the geographical North Pole. So the bear was a polar bear. 

It was white.

The neat thing about this riddle is that it does not seem mathematical at all, what's with the question seemingly not related to the clues given. The additional deduction (North Pole --> polar bear) is witty, to say the least.