Echidna

A spiny egg-laying mammal of Australia and New Guinea — one of only five surviving monotremes — that uses an electroreceptive snout to locate buried ants, termites, and earthworms without using sight or smell.

One of five egg-laying mammals

Monotremes — mammals that lay eggs — are the oldest surviving mammalian lineage, branching from the main mammalian line over 180 million years ago. Only five species exist today:

Short-beaked echidna (Tachyglossus aculeatus) — Australia and New Guinea
Three long-beaked echidna species (Zaglossus spp.) — New Guinea only; all Critically Endangered
Platypus (Ornithorhynchus anatinus) — eastern Australia

The echidna is the most widespread and abundant of the five.

Electrosensory hunting

The echidna’s snout contains electroreceptors that detect the tiny electric fields generated by muscle activity in soil invertebrates. In water, the platypus uses a similar system but far more densely packed. On land, where dry soil doesn’t conduct electricity as well, echidna electroreception is supplementary to smell — but in moist soil, it can locate prey without any visual input at all.

No nipples, no problem

Echidnas have no nipples. Milk is secreted through two patches of specialized skin in the pouch, and the puggle (hatchling) laps it up rather than suckling. The egg is incubated in the pouch for 10 days; the puggle then develops in the pouch for 45–55 days before the spines emerge and the mother moves it to a burrow.

A record-holder for sleep

Echidnas enter one of the deepest known torpors of any mammal during cold weather, with body temperature dropping to near ambient. They have been recorded sleeping for up to 22 hours a day during torpor periods and are among the longest-sleeping mammals when measured across a full year.

Brain size

Relative to body weight, echidnas have a disproportionately large neocortex — larger in proportion than humans. The reason is not fully understood; it may relate to their complex electrosensory processing or unusual social behaviors.