Ingo Arndt / Japanese macaque being groomed in hot thermal spring {Macaca fuscata} Joshin-etsu NP, Japan

Ingo Arndt / Japanese macaques with young in hot spring {Macaca fuscata} Joshin-etsu NP, Japan

Ingo Arndt / Japanese macaque warming in hot thermal spring {Macaca fuscata} Joshin-etsu NP, Japan

Ingo Arndt / Japanese macaque warming in hot thermal spring {Macaca fuscata} Joshin-etsu NP, Japan

Ingo Arndt / Japanese macaques warming in hot thermal spring {Macaca fuscata} Joshin-etsu NP, Japan

Anup Shah / Japanese Macaque (Macaca fuscata) baby sitting on the edge of thermal hotspring pool. Jigokudani Yean-Koen National Park, Japan, February.

Paul D Stewart / Aerial view of Grand Prismatic thermal spring in Yellowstone National Park, USA. The bright colours are natural, coming from thermophile bacteria in the water. People can be seen walking on the raised...

Jeff Vanuga / Thermal hot spring at Mud Volcano, Hayden Valley, Yellowstone National Park, Wyoming, USA.

Jeff Vanuga / Dead Thermal Spider encased in thermophilic bacteria in hot Spring, Yellowstone National Park, Wyoming, USA, October

Ingo Arndt / Japanese macaques grooming in hot thermal spring {Macaca fuscata} Joshin-etsu NP, Japan. These primates can survive winter temperatures below -15 degrees by bathing in the springs

Nick Garbutt / Morning Glory thermal pool surrounded by snow, coniferous forest in background. Near Daisy Geyser Basin, Yellowstone National Park, USA. January 2019.

Nick Garbutt / Algal mats in front of Punch Bowl thermal pool. Near Daisy Geyser Basin, Yellowstone National Park, USA.