Next to the koala and kangaroo, Australia’s most iconic animal is the platypus (Ornithorhynchus anatinus). So uniquely odd is the platypus that when the first (dead) specimens were sent back to England they were considered hoaxes.
Platypuses are superbly adapted to their aquatic environment. They have flat, streamlined bodies and extensive webbing on their powerful front feet which propels them through the water. Like humans but unlike most other aquatic animals they swim by using alternative strokes of their front limbs.
The back feet are used as rudders and brakes whilst the paddle-like tail acts as a stabiliser and as fat storage (holding up to 40% of the platypus’ total weight). The fur is dense and waterproof thus providing excellent insulation. Eyes and nostrils which shut when diving underwater are relatively small and placed dorsally in a groove.
The famous ‘duck bill’ is covered by soft sensitive skin and incorporates the platypus’s ‘super sense’, about 40,000 electroreceptor cells which, similar to sharks, allows them to pick up on the electrical signals of prey animals such as larval insects and small crustaceans.
Instead of teeth adults have flat pads of gum tissue with which they grind their prey, and cheek pouches in which to store it.
They also have unusually low body temperature for mammals of 32 degrees Celsius and can maintain this constantly even during long submersions in water as cold as 4 degrees. Research has shown that they also slow their heart rate when diving from a normal rate of 140-230 beats per minute to 10 to 120. Their blood oxygen levels also fall rapidly but are restored just as quickly once surfaced.
They range in length from 38 to 60 cm with males generally larger than females. Mainland platypuses are generally smaller than those found in Tasmania. The fur is dark to light brown on top with a lighter underside and white patches under the eyes.
Males have a spur on the inner side of each ankle which can release a venom powerful enough to kill small animals and cause intense pain in larger ones, including humans. It is thought that this is used mostly in self-defence but can also play a role in territorial and dominance disputes during breeding season.
Probably the most remarkable thing about the platypus is, along with echidnas, that they are the world’s only living monotremes. This means that although classified as mammals (warm blooded) they lay eggs rather than give birth to live young. They also lactate or feed their young milk from mammary gland ducts although they do not have nipples. Rather the milk oozes out and collects in grooves where the young lap it or suck it from tufts of fur.
Monotremes are considered to be ancient species with the first fossil records of platypus-like creatures dating back to 110 million years ago when Australia was still part of the Gondwana landmass along with South America and Antarctica.
Today there is still not a lot known about platypuses although fears that they may be in decline is prompting a renewed focus from conservation groups, university researchers and government bodies alike, including our MidCoast Council.
Historically platypuses have been found in a wide variety of fresh water habitats in the Eastern States (with the exception of Far North Queensland) from alpine areas to coastal fresh waters. However their secretive natures mean they are rarely seen. They forage mostly between dusk and dawn although sometimes they will be sighted in daylight, particularly if it is cloudy or there is limited food.
During the daylight hours most will usually be hidden away in burrows. They prefer to dig or occupy burrows in steep stable river and creek banks that contain roots and overhanging vegetation including trees. Burrows are typically 3 to 6 metres long and can be blocked with plugs of compacted soil.
Platypuses are typically solitary animals and territorial except when breeding, usually in August. Males will fight each other during the breeding season using their ankle spurs and inflict significant wounds. Courtship and mating occurs in the water and involves a slow dance wherein the male holds the female by the tail with his bill while the female leads them both through a series of circles, twists and turns on the water surface.
Once mating has occurred Platypuses return to their solitary ways with the male taking no part in rearing the young. Females will construct specially built nursery burrows where usually two leathery eggs are laid. Gestation is between two weeks and a month. The female incubates the eggs by curling around them with her tail touching her bill. After another 6 to 10 days the tiny young platypuses, called puggles, will hatch from their eggs with the aid of special egg teeth.
The young grow quickly increasing their weight up to 20 times from hatching and after three to four months become independent, usually between January and early March. They reach adult size between 12 and 18 months and sexual maturity at 18 months. They have been known to live for 20 years in the wild and nearly 23 years in captivity.
Platypuses face a number of threats. Chemical spills into waterways, droughts, and sedimentation washing in from developments have all been known to wipe out populations. Foxes and feral cats can prey on them when they are forced to travel overland in search of new territories or deep enough pools during drought periods. Impact on their prey from fertilisers and other chemicals can also threaten their ability to survive.
Loss of habitat in terms of appropriate banks with vegetation through floods, urbanisation, agriculture, dams and excessive water harvesting are major threats. It is believed that suitable platypus habitat may have shrunk by over 22% in the last 30 years.
A number of platypuses near urban areas have died as a result of entanglement in plastic or rubber loops, cable-ties, plastic bracelets, hair bands and discarded fishing tackle. Illegal nets can also cause drownings.
Their status was listed as ‘Near Threatened’ in 2016 but there are fears that there have been further undocumented declines in numbers since then.
Currently researchers are attempting to identify platypus numbers and genetic resilience in the Midcoast and other areas. Neighbouring land-owners can become involved is assisting this vital work through the Midcoast River Revival Project (search River Revival on MidCoast Council website or contact Alisha Madsen catchment officer at email@example.com 0436298486.