How does dense fur keep a platypus warm and dry?

The platypus is well-adapted for its aquatic lifestyle through the use of dense, waterproof fur that provides essential insulation. This coat consists of long guard hairs that protect a layer of soft underfur, which remains dry even after the animal has spent hours in the water.1

In addition to the protective properties of its fur, the platypus utilizes its burrow to help maintain the condition of its coat; the entrance of the burrow is specifically sized to squeeze excess moisture from the fur as the animal enters. These adaptations allow the platypus to maintain a constant body temperature even when foraging in cold water.1