Stranger fic­tion

A mammal that lays eggs and se­cretes venom, the pe­cu­liar platy­pus has been fas­ci­nat­ing sci­en­tists since the 19th cen­tury but faces an un­cer­tain fu­ture.

BBC Wildlife Magazine - - Platypus - By Linda Vergnani Pho­to­graphs Doug Gimesy

Afurry an­i­mal with a body the size of a hot-wa­ter bot­tle is ca­vort­ing through the wa­ters of a clear, blue stream emerg­ing from Jenolan caves, three hours west of Syd­ney. There is a splash as it dives down, pad­dling vig­or­ously with its webbed front feet. When it reaches the bot­tom, the an­i­mal be­gins sweeping its flat, duck-like bill back and forth above the silt. The platy­pus is us­ing thou­sands of minute re­cep­tors in its bill to de­tect the elec­tri­cal fields made by the mus­cle

move­ments of its prey – mainly in­sect lar­vae, aquatic in­sects, and some­times fresh­wa­ter cray­fish and shrimp.

It is rel­a­tively easy to spot a platy­pus in the limpid stream and Blue Lake at Jenolan, but nor­mally they are far harder to de­tect. Their water­proof brown coats of­fer good cam­ou­flage against the earthy banks of the per­ma­nent rivers, creeks, lakes and wet­lands they in­habit in eastern Aus­tralia.

They’re also largely noc­tur­nal, and usu­ally spend the day sleep­ing in their bur­rows, which may be up to 30m long, in the river banks. They emerge at dusk to hunt for their

aquatic prey and re­treat at dawn. Fe­males weigh 600–1,750g, while males are a heftier 800–3,000g (platy­puses in north Queensland are about half the weight of those in Tas­ma­nia).

This cu­ri­ous crea­ture is a monotreme: a form of egg-lay­ing mammal that suck­les its young. It has a sin­gle ori­fice – the cloaca – used for uri­na­tion, defe­ca­tion and re­pro­duc­tion. The only other monotremes are four species of echidna, but these are very dif­fer­ent look­ing, spiny land dwellers.

Tom Grant, au­thor of the nat­u­ral his­tory guide Platy­pus, spent over 40 years re­search­ing platy­puses on a 5km stretch of the Shoal­haven River in New South Wales. He mi­crochipped 812 in­di­vid­u­als and found the old­est fe­male platy­pus in his study was still breed­ing af­ter 21 years.

Would you be­lieve it?

When dried spec­i­mens of this species were first sent to Europe at the end of the 19th cen­tury, some nat­u­ral­ists thought the an­i­mal was a fake, as­sem­bled by a wily taxi­der­mist. Not only did it have a duck-form bill and a beaver tail, but the an­i­mal laid eggs like a snake or bird.

Tom says the bill is ac­tu­ally noth­ing like a duck’s bill. “It feels like kid leather and is very soft, pli­able.” Up close, the thou­sands of elec­tro and touch re­cep­tors that give the an­i­mal a ‘sixth sense’, look like tiny pores cover­ing the sur­face of the bill.

In his book, Tom de­scribes how, af­ter mat­ing, the fe­male platy­pus lays up to three eggs in a nest of wet veg­e­ta­tion that she makes in a cham­ber in one of her bur­rows. The fe­males are thought to in­cu­bate the eggs by curl­ing their bod­ies around them.

When the young hatch af­ter about 10 days, the mother feeds them from two milk patches (are­o­lae) on her chest. The nestlings lick the milk off their mother’s fur, as the platy­pus has no teats.

Tom says though the platy­pus is an iconic an­i­mal, sci­en­tists still don’t know much about its ecol­ogy. Pro­fes­sor Richard Kings­ford, Di­rec­tor of the Cen­tre for Ecosys­tem Science at the Univer­sity of New South Wales, says, “They’re very dif­fi­cult to work on be­cause they keep un­godly hours and they’re very cryptic.”

It is hard to get quan­ti­ta­tive data on the platy­pus. At the turn of the 19th cen­tury, “tens of thou­sands of these crea­tures were killed for their fur,” says Richard, and the species never re­ally re­cov­ered. It wasn’t un­til 1912 that the species was of­fi­cially pro­tected in all states.

Richard led a na­tional risk as­sess­ment study into platy­puses, which showed a “wor­ry­ing” 30 per cent de­cline in platy­pus num­bers – from an es­ti­mated 300,000 when Eu­ro­pean set­tlers colonised Aus­tralia 200 years ago to 200,000 or fewer now. The re­searchers based the pro­jec­tions on his­toric re­ports of platy­puses as well as cur­rent re­search across 300km of river in four states. Richard says, “We have great con­cerns about the fu­ture sur­vival of this unique species”. The platy­pus is listed as Near Threat­ened on the IUCN Red List.

The study is part of the Platy­pus Con­ser­va­tion Ini­tia­tive (PCI), which aims to re­duce the risk of the species be­com­ing ex­tinct, and bet­ter con­serve the wild pop­u­la­tions. It in­cludes re­searchers from three uni­ver­si­ties and Syd­ney’s Taronga Zoo as well as a pri­vate con­sul­tancy Ce­sar.

Re­searchers can­not at­tach ra­dio col­lars to platy­puses, for fear the an­i­mals might drown.

The an­i­mals are dif­fi­cult to track in the wild. Re­searchers can­not at­tach ra­dio col­lars to platy­puses for fear they might stran­gle or drown as they for­age be­tween sub­merged roots and branches, ac­cord­ing to Richard. For the past three years, his team has fit­ted some platy­puses with acoustic tags and tracked their move­ments with lis­ten­ing sta­tions along cer­tain river­banks.

Han­dle with care

Sci­en­tists cap­tur­ing platy­puses in the wild take great care to avoid the venom spurs on the hind an­kles of the males. Used in fights against ri­vals, the com­plex venom in­jected through the spurs causes agony in hu­mans.

Gi­lad Bino, re­search fel­low at the Cen­tre for Ecosys­tem Science, re­mem­bers the adren­a­line rush when he and a vet­eri­nar­ian from Taronga Zoo un­tan­gled their first wild platy­pus. It was caught in a fyke net (an un­weighted mesh net, which al­lows the platy­pus to sur­face) they had set up on the Sev­ern River. The sci­en­tist was re­search­ing the im­pact of dams and river reg­u­la­tion on the health of platy­puses for the PCI.

The semi­aquatic platy­pus has webbed feet and a duck­like bill. When the first dried spec­i­mens were brought to Europe, sci­en­tists be­lieved they were a hoax.

Clockwise from top left: a platy­pus re­search project in the Snowy River; mea­sure­ments are taken to com­pare pop­u­la­tions; fyke nets are checked ev­ery four hours.

Once highly sought af­ter by the fur trade, the thick, water­proof fur of the platy­pus helps to in­su­late this species in the wa­ter.

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