How can platypuses maintain body temperature in very cold water?

The platypus maintains a constant body temperature even in very cold water—sometimes as low as 4 °C (39 °F)—primarily through the use of dense, waterproof fur that provides excellent insulation.1

While the platypus has an unusually low body temperature for a mammal (approximately 32 °C or 90 °F), it is capable of thermoregulation. Its coat consists of long guard hairs that protect a layer of soft underfur, which remains dry even after the animal has spent hours submerged. This specialized insulation prevents excessive heat loss, allowing the platypus to remain active in cold aquatic environments without the need for hibernation.1