Photographer Captures Hilarious Close Up Portraits of Some of the World's Most Unusual Primates

For over two decades, photographer Mogens Trolle has captured stunning wildlife photos on all seven continents. Trained as a zoologist and wildlife biologist, he specializes in mammals and uses his knowledge of them—as well his keen eye—to capture each creature’s unique personality.

Only one monkey troop in the world frequents a hot spring, the one at Jigokudani in the cold mountains of Japan. Here two mothers and their young. Dominant females spend more time at the spa than subordinate females, so getting to use the thermal pool is a privilege. Infants of dominant females get to bath more than children of females further down the social ladder. Males that migrate into the Jigokudani troop as adults never acquire the habit of bathing in the hot spring. It is a habit you only learn as a kid.