Which egg-laying mammal enters hibernation during the Australian winter?

The short-beaked echidna is the egg-laying mammal that enters hibernation during the Australian winter.

It is one of only five living monotreme species, the small group of mammals that reproduce by laying eggs. The short-beaked echidna, Tachyglossus aculeatus, is widespread across Australia and also occurs in parts of New Guinea. Despite its spines and insect-eating lifestyle, it is a true mammal and nurses its young with milk.

During the Australian autumn and winter, echidnas undergo repeated bouts of torpor and deep hibernation. Their body temperature can fall dramatically, their heart rate slows to only a few beats per minute, and metabolism may drop to about one-eighth of its normal rate. Warmer intervals bring brief arousals.

The platypus is the common mix-up: it is also a monotreme, but it is not known for entering hibernation. Bilbies and numbats are marsupials, not egg-laying mammals. Echidnas emerge as conditions warm, with seasonal activity closely linked to feeding and reproduction.