9.5.1 The Monotremes
Description
This article is from the soc.culture.australian FAQ, by Stephen Wales with numerous contributions by others.
9.5.1 The Monotremes
[AT] The most remarkable of Australia's Gondwanan passengers are the
Platypus and echidnas. These are egg-laying mammals known as the
monotremes. Female monotremes incubate their eggs for 1-2 weeks.
After hatching the young depend on milk secreted by their mother for
3-5 months. Monotremes occur only in Australian and New Guinea.
[RG] The Echidna is a small termite eating monotreme. The Echidna's
back is covered with spines (a similar defense system to the
porcupine, though the two animals are not related). It's short legs
are adapted for digging - the forelegs for digging into termite
mounds, and the hind legs for digging into the ground. The animal's
defense is to quickly bury itself while raising the spines. Very few
predators are capable of attacking the Echidna (though I believe
Dingos have managed to). The Echidna is one of the world's two
monotremes (the other of which is the Platypus) which are the only egg
laying mammals. It's species name is Tachyglossus Aculeatus. Many
people in Australia mistakenly call them "porcupines", though a more
correct colloquial name for them is the Spiny Anteater.
[AT] To be picky there actually two species of Echidna and hence 3
extant monotreme species. The Long-Beaked Echidna (Zachyglossus
bruini I think) is found in Papua New-Guinea. The Short-Beaked
Echidna is found in both PNG and Australia. Both species have been
split in the past. Echidnas also eat ants and occur in areas without
termites but not in areas without ants (but maybe there are no areas
with termites but no ants).
Like the Platypus, Echidnas possess receptor capable of detecting
minute electrical currents. The Platypus presumably uses them for
detecting the nerve impulses of prey. Its not obvious how the
Echidnas' receptors are useful. One suggestion is that they allow
detection of trace concentrations of gases associated with termite
colonies when the gases dissolve on the Echidna's snout and produce
minute electrical currents.
Also remarkable is the diversity of habitats Short-Beaked Echidnas
occupy. Everything from the arid interior to alpine areas of the Snowy
Mountains. In the last 2-3 years researchers have monitored Echidnas
in the Kosciusko high country through the winter and found their
temperature regulation more complex than previously thought. In the
past it was suggested monotremes had primitive temperature regulation
because they maintain a lower temperature than placentals and it
fluctuates more. Clearly its not that simple and their temperature
regulation may be as well-adapted as many placental mammals.
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