Macropus

• Their shuffling walk, inquisitive gaze and protective spines are unmistakable, coupled with the coarse hair and stubby beak.
• Australia has just one species, the short-beaked echidna (Tachyglossus aculeatus), which roams virtually the entire continent.
• Tasmanian echidnas are much hairier and Kangaroo Island echidnas join long mating trains.

1: They’re ancient egg-laying mammals

• Our familiar short-beaked echidnas can weigh up to six kilograms – but the Western long-beaked echidna can get much larger at up to 16kg.
• These ancient mammals lay eggs through their cloacas (monotreme means one opening) and incubate them in a pouch-like skin fold, nurturing their tiny, jellybean-sized young after hatching.
• That’s because platypus fossils go back about 60 million years and echidnas only a quarter of that.
• Read more:
  Curious Kids: How does an echidna breathe when digging through solid earth?

2: From deserts to snow, echidnas are remarkably adaptable

• You can find echidnas on northern tropical savannah amid intense humidity, on coastal heaths and forests, in arid deserts and even on snowy mountains.
• The one most of us will be familiar with is Tachyglossus aculeatus aculeatus, widespread across Queensland, New South Wales, South Australia and Victoria.
• Kangaroo Island echidnas have longer, thinner, and paler spines – and more of them, compared to the mainland species.
• Tasmanian echidnas are well adapted to the cold, boasting a lushness of extra hair.

3: Mating trains and hibernation games

• You might have seen videos of Kangaroo Island mating trains, a spectacle where up to 11 males fervently pursue a single female during the breeding season.
• Pregnancy usually lasts about three weeks after mating for Kangaroo Island echidnas, followed by a long lactation period of 30 weeks for the baby puggle.
• T. aculeatus aculeatus has a similarly short lactation period (23 weeks), but rarely engages in mating train situations.
• After watching the pregnancies of 20 of these echidnas, my colleagues and I discovered this subspecies takes just 16–17 days to go from mating to egg laying.

4: What do marsupials and monotremes have in common?

• Marsupials bear live young when they’re very small and let them complete their development in a pouch.
• Despite this key difference with monotremes, there’s a fascinating similarity between Australia’s two most famous mammal families.
• At 17 days after conception, the embryo of the tammar wallaby (Macropus eugenii) hits almost exactly the same developmental milestone as echidna embryos.
• Monotremes branched off from other mammals early on, between 160 and 217 million years ago.