Diane McAllister / Japanese Macaque (Macaca fuscata) pair rest together on a rock near the river in Jigokudani, Japan.

Diane McAllister / Japanese Macaque (Macaca fuscata) adult with wet snowy head in the hot springs of Jigokudani, Japan.

Diane McAllister / Japanese Macaque (Macaca fuscata) juvenile riding on its mother's back, along snow trail in Jigokudani, Japan.

Diane McAllister / Japanese Macaque (Macaca fuscata) adult in the hot springs of Jigokudani, in the snow, Japan. February

Diane McAllister / Japanese Macaque (Macaca fuscata) juvenile portrait, Jigokudani, Japan. February

Wim van den Heever / Japanese macaque (Macaca fuscata) still soaked from climbing out of the hot spring, Jigokudani, Nagano, Japan.

Wim van den Heever / Japanese macaque (Macaca fuscata) sitting portrait, Jigokudani, Nagano, Japan.

Wim van den Heever / Japanese macaque (Macaca fuscata) drinking at hot spring, silhouetted in mist, Jigokudani, Nagano, Japan.

Wim van den Heever / Japanese macaque (Macaca fuscata) a playful youngster launches out the tree onto the snow below, Jigokudani, Nagano, Japan.

Wim van den Heever / Japanese macaques (Macaca fuscata) huddling together to keep warm, Jigokudani, Nagano, Japan.

Wim van den Heever / Japanese macaque (Macaca fuscata) playful youngter hanging from tree, Jigokudani, Nagano, Japan.

Wim van den Heever / Japanese macaque (Macaca fuscata) two youngsters playing in tree, Jigokudani, Nagano, Japan. February.