Crawling through a writhing pit of 75,000 snakes may not be everyone's idea of a great day at work, but it was for Paul Colangelo.

The National Geographic grantee recently gained new appreciation for the reptiles while photographing the world's largest gathering of snakes in the Narcisse Snake Dens of Manitoba, Canada (map).

Each spring, masses of red-sided garter snakes congregate inside limestone caves to form mating balls, in which up to a hundred male snakes vie for a single female. She, in turn, "is desperately trying to get out of the pit," said Colangelo, an environmental documentary photographer.

These slithery swarms appear to be a "frenzy, but a closer look reveals a much finer dance,"