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Platypus in Hornsby Shire

platypus swimming in water

Using Hornsby Platypus eDNA as a Healthy Waterways Catalyst

In August 2022, the first ever confirmed sighting was made of a platypus within the rural catchment of Colah Creek. Prior to this, platypus were not known to inhabit any waterway within Hornsby Shire and it was assumed that they were locally extinct.

This sighting inspired a citizen science platypus eDNA research pilot project proposal.

In partnership with three local community groups (Streamwatch, Still Creek Catchment Landcare & Friends of Berowra Valley), Council was successful in receiving $10,000 for a Sydney Water ‘Healthy Waterways’ Community Grant for the project “Using Hornsby Platypus eDNA as a Healthy Waterways Catalyst”. These Community Grants are extremely popular, and this was one of only seven grants allocated for 2022.

The project aimed to gain a better understanding of platypus distribution within Hornsby’s rural creeklines, improve riparian platypus habitat, and build community knowledge for improved environmental awareness and outcomes in the catchment. Our project idea was inspired by the platypus eDNA research and community education being undertaken by Cattai Hills Environment Network (CHEN) within The Hills Shire.

Most of the funding was used to undertake environmental DNA (eDNA) testing – an innovative, non-invasive sampling technique that analyses a small water sample for traces of DNA left by fauna that use the waterbody – to establish if platypus are living within rural creek catchments of Hornsby Shire.

  • eDNA training workshop with a platypus research expert
  • 2 x eDNA sampling field days on the 17 and 27 November 2022 (30 Citizen Scientists sampling 23 creek locations within the Still Creek, Halls Creek, George Hall Creek, Colah Creek and Glenorie Creek Catchments)
  • Platypus Q&A session and Habitat Planting Day (36 attendees who planted 224 ‘platypus-friendly’ riparian plants along Colah Creek)
  • A letter from the Mayor of Hornsby was sent to rural residents advising them of the project and seeking local knowledge or sightings of platypus
  • A Colah Creek-focused platypus brochure "Introducing your special neighbour" was produced and sent to rural residents
  • Produced a map highlighting locations of the platypus eDNA creek sampling sites
  • platypus@hornsby.nsw.gov.au email address set up to encourage community feedback
  • A number of articles on the project appeared in local media

Platypus eDNA monitoring was completed at 23 creekline locations on 17 and 27 November 2022. The results of the monitoring were then processed at the Sydney Water laboratories with the unfortunate result of no fragments of platypus DNA being detected.

While the analysis by Sydney Water scientists showed no sign of the iconic species, the timing of sampling could have been a contributing factor. Although no platypuses were detected in these samples, it still provides a reminder of the diversity of wildlife that lives downstream from our residential and commercial areas.

In hindsight, we now know from our platypus experts that by November most female platypus have gone into their burrows to nest. The eDNA testing method shows when a platypus is present in the last 24 to 48 hours at a given location. Therefore, it does not reveal population numbers nor confirm that there are no platypus present - it could simply mean that there is a very small population present and that they were either holed up in a burrow or at another location during the sampling timeframe. Heavy rainfall in the months preceding sampling could also be a contributing factor for the nil result.

The visual sighting of a platypus by Hornsby Shire Council staff on 4 August 2022 means that at least one platypus utilises Colah Creek as habitat. Despite our eDNA monitoring results, the engagement with the community and raising awareness of platypus within the Shire was very beneficial and is a positive step in encouraging the local catchment community to care for the health of their local waterways and the critters that live within it.

This pilot eDNA creek sampling project inspired the subsequent Shire-wide metabarcoding eDNA Citizen Science-focused project: “Communities, Creeks & Critters – eDNA Social Cohesion Project”.

eDNA, or environmental DNA, is a cutting-edge technology used for wildlife detection and monitoring. It is a non-invasive sampling technique that is gaining popularity due to its effectiveness and cost-efficiency.

All animals release DNA into their surroundings, such as through mucus, faeces, urine, gametes, and skin cells. Scientists can now extract and analyse DNA from water, air, or soil samples to trace the presence of various species. For instance, a water sample can capture evidence of a platypus being in a creek within the past 24-48 hours.

How does eDNA work?

There are two methods for identifying sources of eDNA:

  1. DNA Barcoding: This method targets a specific gene to detect a single species. It was utilised in the Hornsby platypus eDNA pilot project.
  2. DNA Metabarcoding: This method identifies all the species present in a sample.

Platypus Facts

The plural of platypus has been long-established in the English-speaking world as platypuses.

This is due to the Greek root of the name ("flat-foot"). The actual Greek plural for platypus is platypodes, but this isn't used in English. As for “platypi”? Well, English is an evolving language, and common usage sometimes dictates a word's acceptance. So, using platypi may be fun and quirky, but strictly speaking, it's not correct.

The platypus (Ornithorhynchus anatinus) – or duck-billed platypus - is:

  • a unique, venomous, semi-aquatic mammal that lays eggs and uses its super sensory bill – like an electric sixth sense - to hunt prey in murky water
  • one of very few venomous mammals in the world. The spur on the male’s hind foot is connected to a venom-secreting gland and is likely used in aggressive encounters between rival males
  • not considered endangered but the International Union for Conservation of Nature has upgraded their status to 'Near Threatened'
  • protected by legislation in all of Australia's eastern states
  • threatened with local extinction in areas where they once thrived due to bush fires, drought, deforestation, predation, and pollution of waterways
  • the animal emblem of NSW and well-known animal symbol of Australia
  • famous as the mascot for the Sydney 2000 Olympics
  • along with the echidna, the only mammals that lay eggs - they also feature on our 5 cent and 20 cent coins
  • The name Platypus comes from the Greek word for ‘flat-footed’ – they're very awkward on land, walking on their knuckles to protect the webbing of their feet
  • Baby platypuses are called “platypubs” (and baby echidnas are called “puggles”).

Platypuses occur in freshwater systems from tropical rainforest lowlands and plateaus of far northern Queensland to cold, high altitudes of Tasmania and the Australian Alps. Elusive by nature, there’s a lack of reliable data about where and in what numbers they occur. Their distribution is unpredictable, as they appear to be absent from some relatively healthy rivers yet have been found in others that are quite degraded.

Platypuses make their home in and near freshwater creeks, slow-moving rivers, lakes joined by rivers, and built water storages such as farm dams.

They build a simple burrow in a riverbank, just above water level and often among a tangle of tree roots.

Hornsby Shire contains many areas that appear to be suitable habit for platypus including the upper reaches of Berowra Creek and Cowan Creek catchments, particularly those areas in rural or undisturbed bushland catchments.

  • The first ever record of a platypus sighting by a European colonist was near the Hawkesbury River in 1797.
  • Platypus were also observed in Epping bushland in the early 1900’s.
  • In 1976, one was observed at Milson Island on the Hawkesbury River just north of Muogamarra Nature Reserve.
  • In 1977, one was observed near Kimmerikong Creek west of Cowan within Muogamarra Nature Reserve itself.
  • In 1982, a platypus was observed on the north side of the Hawkesbury River in Dharug National Park.
  • In 1983, there were two sightings within Ku-ring-gai Chase National Park along Cockle Creek, just South of Bobbin Head; and near the entrance to Cowan Creek on the northern bank.

The platypus usually lives alone, and numbers are most often limited by the availability of food, mainly in the form of tadpoles,water bugs, shrimp, and swimming beetles. When not foraging they spend their time in their burrows which they build in the banks of creeks, rivers, or ponds.

They feed in both slow-moving and rapid parts of creeks and rivers but seem to prefer areas with cobbles and gravel. At times, they use rocky crevices and stream debris as shelters, or they burrow under the roots of vegetation near the waterway. Hence, the ideal habitat for the species includes a river or a creek with earth banks and native vegetation that provides shading of the waterway and cover near the bank.

People hunted the platypus for their fur in the early 1900s, but they're now protected. Platypus populations are believed to have declined or disappeared in many catchments, particularly in urban and agricultural landscapes. Given their dependence on freshwater systems, destruction of creek bank plants, siltation and other waterway pollution are major threats. Water extraction, dams and diversions to water flow have a big impact. Water quality and in-stream habitat (such as submerged roots, branches, and logs) are critical, so degradation of these elements is a threat. Run-off from agriculture (sediments and nutrient load) can degrade platypus habitat. If you catch yabbies, you should know that Opera house-style yabby traps are illegal and have caused many drownings of platypus, native water rat (rakali), and turtles. Please do not use them!

Platypus can be killed by being sucked into the unguarded inlets of irrigation pumps or mini-hydroelectric generators. Water extraction or removal can also contribute to reduced water flow in creeklines and cause a reduction in the overall amount of platypus habitat.

Natural predators of the platypus include snakes, water rats, goannas, hawks, owls, and eagles, yet these are unlikely to have affected overall platypus numbers. Up until the early twentieth century, they were widely killed by humans for their fur, and introduced predators such as foxes, dogs and cats are presumed to have had a major impact on populations.

Platypuses are also vulnerable to the effects of pollution and declining water quality. The misuse of chemicals (such as pesticides, herbicides, surfactants, and fertilizers) near waterways can disrupt the aquatic food chain, greatly reducing the platypus food supply. For the platypus to stay warm while in the water, its fur must remain completely clean and waterproof, and not be fouled by oil or other pollutants. Furthermore, they are not adept at removing objects caught around the head or body and can die after becoming ensnared in litter such as loops of nylon fishing line or even hair tie elastics.

Platypus and their food species struggle to survive in areas where native vegetation has been cleared from creeks and riverbanks. Furthermore, due to Hornsby’s ridge top style development, and past poor building site sediment control practices, many of the deeper ponds along our local creeklines have been filled with sediment from urban run-off. The expansive hard surfaces and stormwater systems of our urban areas have created fast-flowing, high-energy surges whenever it rains. Such conditions may not be ideal habitat for platypus nor their prey.

As part of a worrying trend, the platypus has been in decline across much of its traditional range due to river mismanagement, habitat destruction, predation by invasive species, and an increased frequency and severity of droughts and fires due to climate change. The future of this extraordinary monotreme lies in the balance. Platypus are facing a silent extinction and it is vitally important for all of us to take action to protect them and their habitat

Please don't disturb platypus if they live in creeklines on your property or in your local catchment.

You can help the platypus living in your area by planting and maintaining locally native riparian-friendly plants along waterways. If you do this, you will protect the creek banks and provide areas for the platypus to live.

To prevent platypus and other aquatic wildlife from drowning or otherwise dying after being sucked into water extraction pumps or water-powered generators, a mesh cover or equivalent barrier should be fitted at an appropriate distance around all intake points and checked regularly.

Spread the word among friends and acquaintances that Opera House-style yabby traps and homemade equivalents are responsible for drowning many platypuses, Australian water rats (Aboriginal name, Rakali) and freshwater turtles each year. From 30 April 2021 yabby traps (“opera house”) are illegal and no longer permitted in NSW waters.

Don't let your dogs and cats wander unsupervised at night - this will help safeguard the welfare of your pets as well as wildlife. Obey local laws which prohibit the presence of unleashed pets in Wildlife Protection Areas. Even during the day, uncontrolled dogs and cats can disrupt the natural behaviour of platypus and other native species occupying such habitats.

And remember – whatever goes down the drains of our stormwater system ends up in the local creek – where the platypus are trying to survive.