Guidelines for Agencies

Platypus Conservation Guidelines for Management Agencies and Environmental Groups

1. Planning for platypus

The platypus is an important part of reliable freshwater environments in Australia and an excellent indicator of the productivity of aquatic systems. Conditions that are right for the platypus, a generalised top predator, will by definition favour many other native freshwater species. Accordingly, measures that enhance the quality of platypus habitat tend to promote biodiversity in general. The platypus is also a powerful and popular wildlife icon to harness community support on behalf of environmental action.

Catchment Management Authorities and other relevant agencies should ensure that platypus conservation requirements are routinely considered when developing catchment-wide environmental action plans or considering major changes to the flow regimes of water bodies in highly regulated systems. Likewise, local councils and regional planning bodies should take into account the species’ needs when contemplating new developments or changes to zoning. Councils and managers of public land should also check that on-ground works in their areas are carried out in a manner that is sympathetic to these animals’ survival.

Similarly, Landcare groups and other community-based organisations working to improve the environmental quality of streams, lakes and rivers should try to assist local platypus populations whenever possible.

Some of the key platypus-related issues that need to be taken into account by management agencies and environmental groups are discussed in the sections below.

2. Maintaining or restoring bank and channel stability

Actively eroding banks do not provide secure burrow sites for platypus, and the resulting sediment can seriously degrade the quality of platypus foraging habitat when it enters the water.

Unfortunately, many Australian waterways continue to suffer from unnaturally high rates of erosion along the banks and/or channel. This is true both in urban areas where run-off from hard surfaces like roads and roofs vastly increases the volume and speed of water flows after storms and in farming areas where protective vegetation has often been cleared right to the edge of the water.

In places where banks are bare and vulnerable to further erosion, a combination of management actions may be needed to halt and reverse the trend.

What can be done to protect platypus:

  • Grade control structures, such as rock chutes or weirs, may be required to stabilise the stream bed. Besides working to control erosion, such structures often increase habitat diversity and thereby immediately improve conditions for fish, aquatic invertebrates and platypus.
  • The vertical slope of a vulnerable bank may need to be reduced (or its toe protected with large rocks or other structures) while vegetation has a chance to become established.
  • Grazing pressure by livestock along the edge of a waterway may need to be controlled to achieve sustainable levels – this may require additional fencing or the provision of formed (or off-stream) watering points.
  • Grazing pressure by rabbits or other feral animals may need to be eliminated.
  • Significant disturbance to creek or river banks should be followed as soon as possible by an appropriate revegetation program, ensuring that ground cover plants as well as trees are re-established. (On the other hand, lining substantial sections of the banks or channel with concrete to stop erosion should also be avoided in order not to “seal off” natural habitats from platypus and other freshwater species.)
  • Take care to control soil loss from construction sites (or other patches of disturbed ground) when these are located next to natural water bodies or gullies leading to natural water bodies.

3. Managing stormwater drainage

Storm run-off from roofs, roads and other hard surfaces can carry a wide range of pollutants into water courses. It also promotes bank and channel erosion, particularly when impervious surfaces drain rapidly to creeks and rivers via sealed drains or pipes, with very adverse consequences for platypus habitat quality.

What can be done to protect platypus:

  • Direct connected imperviousness in stream and river catchments (either those supporting a platypus population or where there is a reasonable likelihood that a population could become established if other limiting habitat factors are improved) should be limited to a value well below the critical threshold limit for platypus of 2.2%.
  • Ensure that water-sensitive urban design principles are applied to new housing estates, shopping centres, industrial parks etc. to reduce the impact of associated run-off on creeks and rivers (e.g. see http://www.clearwater.asn.au). Ensure that run-off from sealed roads in suburban or country areas is designed to drain to vegetated swales as opposed to concrete drains leading to waterways.
  • If you live in an area that is serviced by conventional stormwater drains, install a home water tank so rain falling on your roof can be stored and used to water the garden.
  • Gross pollutant traps should be installed on stormwater drains as required to minimise the amount of litter and other materials that are harmful to platypus entering waterways.

4. Weed control and revegetation

Riparian vegetation undoubtedly contributes to platypus well-being, by providing protective cover for the animals and their burrows and promoting favourable habitat conditions for their invertebrate prey. In an urban context, maintaining a substantial corridor of ideally indigenous vegetation along waterways will help to screen out noise and artificial light, trap litter and other pollutants, reduce trampling and bank erosion, restrict access by foxes and unsupervised pets, and generally contribute to a more diverse and productive freshwater ecosystem.

Although some introduced plants such as willows appear to have a detrimental impact on the quality of platypus foraging habitat (particularly along smaller streams where willow roots can completely choke the channel), it is important when eradicating non-native plants to try to ensure that bank erosion does not ensue. Particularly in the case of narrow and/or shallow water bodies, platypus survival may be compromised if weed control programs result in inadequate plant cover along the banks, increasing the vulnerability of platypus to predators.

What can be done to protect platypus:

  • Urban (or other) development should never be allowed to encroach unreasonably close to the margins of streams and rivers which support platypus. The reserved strip of riparian land should normally be at least 30 metres wide (though ideally more), in order to support a self-sustaining plant community including mature specimens of the tree species originally found in the area.
  • If time is required to establish riparian vegetation at the edge of a new housing estate or other area of high human activity (such as a shopping mall or recreation facility), consideration should be given to fencing the riparian area at least until trees and shrubs are well established.
  • Willows should be progressively removed from stream and river banks to improve the quality of platypus habitats. To reduce the potential for erosion, areas where willows have been removed should be replanted as soon as possible with appropriate native trees and shrubs.
  • In cases where a weedy plant dominates both banks for a considerable distance (e.g. 200 metres or more), consideration should be given to staging removal programs so the weed is eliminated from one bank in one year and the opposite bank in a later year.
  • Herbicides used to control riparian weeds should never be allowed to enter the water, either directly or through storm run-off. Areas of bare soil developing after use of herbicide should be replanted as quickly as possible with appropriate indigenous species.
  • To avoid damaging platypus burrows, weed removal activities which involve driving over or digging into banks with heavy machinery should be strictly minimised, particularly within about 10 metres of the waters edge. Special care should be taken not to disrupt or cause banks to become compacted in the period when female platypus are raising their young, particularly in areas where many platypus occur.

5. Providing in-stream woody habitat (logs and branches)

The presence of logs and large branches in the water is a very positive habitat feature for platypus, contributing to foraging success and occasionally providing them with shelter sites.

Three studies have been carried out by APC staff to examine whether the amount of woody debris present in stream segments that are intensively used by platypus differs from the amount present in areas that are rarely used. In each case, the amount of woody debris was estimated by counting the number of logs and large branches projecting above the water surface during periods of normal base flow.

In brief, it was found that areas regularly used by radio-tagged platypus along two creeks in the Yarra River catchment respectively held an average 21 logs and large branches (≥ 20 cm in diameter at the surface) per 100 metres of channel and 26 logs and large branches (≥ 10 cm in diameter at the surface) per 100 metres of channel. Similarly, along the upper reaches of the Wimmera River in western Victoria, areas supporting reasonably high numbers of platypus held an average 22 logs or branches (≥ 20 cm in diameter at the surface) per 100 metres of channel. In contrast, channel segments that were rarely used by platypus respectively held an average 11 logs and large branches (≥ 20 cm in diameter at the surface) per 100 metres of channel (Running Creek), 12 logs and large branches (≥ 10 cm in diameter at the surface) per 100 metres of channel (Little Yarra River) and 8 logs or branches (≥ 20 cm in diameter at the surface) per 100 metres of channel (Wimmera River).

What can be done to protect platypus:

  • Logs and large branches should be retained whenever possible in streams, rivers and lakes in order to contribute to the quality of platypus habitat.
  • Based on the studies described above, consideration should be given to augmenting the amount of in-stream woody habitat in the case of streams or small rivers where less than 20 logs or branches project on average above the surface in 100 metres of channel during normal base flow.

6. Maintaining adequate flow in managed river systems

Platypus are adapted to feed exclusively in an aquatic environment. In the absence of adequate surface water, platypus starve. Less extreme reductions in flow regime are likely to be mirrored in reduced reproductive success and, ultimately, reduced population size. Although platypus can survive for a time in isolated pools scattered along the length of a drying water course, mortality is likely to increase in such circumstances due to stress (particularly if animals are crowded together and food is in short supply) and increased exposure to foxes and other predators.

The creeks and rivers of southeastern Australia normally carry the least amount of flow from mid-summer to early autumn, corresponding precisely to the period when juvenile platypus emerge from nesting burrows and have to learn to forage on their own. Their mothers are often in poor condition at this same time (as a by-product of recent lactation) and so are also particularly vulnerable to dying if water courses dry up in late summer.

What can be done to protect platypus:
The ideal flow regime for platypus entails plenty of surface water being available throughout the year in every year. However, if it’s necessary to periodically institute a low (or no) flow regime in a managed river system, adequate surface flow should be maintained from August to June (in order to accommodate the entire platypus reproductive cycle including juvenile dispersal) at least one year in every two in areas of known platypus breeding habitat. In addition, it is essential that sufficient permanent pools are present in the system to sustain platypus populations through low or no flow periods.

To help protect platypus from predators and meet their requirements while foraging, the volume of flow in platypus habitats should be sufficient to ensure that the average depth along runs and pools is at least 0.5 metres (though preferably more) if a channel is more than 5 metres wide, and at least 0.3 metres (though preferably more) if a channel is less than 5 metres wide.

7. Providing refuge areas during drought

Sizable pools have tended to disappear from many creeks and small rivers in the platypus range in line with increased rates of catchment erosion, reduced numbers of large logs in the channel and (in the case of catchments subject to regulated flows) more constant and/or reduced surface flows as compared with historical norms. In turn, this undermines the system’s resilience when challenged by natural or manmade drought, including instances where those charged with managing the system decide to reinstate a natural flow regime (i.e. one that is not augmented by mandated releases of water) downstream of an impoundment. In the absence of substantial deep pools to provide seasonal refuge habitat, many species (notably including the platypus) are liable to become locally extinct as water vanishes from the channel.

What can be done to protect platypus:

  • Management agencies should always consider the role of sizable pool habitats in maintaining the viability of local platypus populations before eliminating them (for example, to remove a redundant weir). Particularly in the case of relatively small creeks, such pools are likely to provide essential habitat for breeding and foraging which in turn plays a key role in maintaining a locally viable platypus population. If such a pool definitely needs to be decommissioned, strong consideration should be given to developing a pool or backwater of at least comparable size and permanence elsewhere along the creek.
  • Research is needed to identify the most practical and cost-effective techniques for restoring (or creating) sizable pools and billabongs in areas where they occurred historically but are now in short supply. There is also an urgent need to identify the most effective protocols for allocating environmental flows to maintain reliable pool habitats in regulated systems.
  • Given the large amount of food typically consumed by a platypus and the correspondingly large size of platypus home ranges, we recommend that a useful platypus drought refuge should ideally measure at least 80 metres in length and comprise 500 square metres of surface area (through ideally more). Alternatively, a more practical option in some circumstances may be to create smaller pools that collectively comprise at least 500 square metres of pool habitat in a chain of ponds.
  • To provide protection from predators and ensure that the water remains reasonably cool (to maintain appropriate conditions for a range of aquatic invertebrates), pools should ideally retain water at a minimum depth of 1-4 metres
  • To provide habitat for platypus burrows, some of the pools perimeter should ideally be bounded by a reasonably steep and well-consolidated earthen bank rising at least 1 metre above the water.
  • Overhanging vegetation should be encouraged to grow around the pool to improve habitat quality and help provide cover from predators. For the same reasons, shrubby vegetation should be encouraged to develop between neighbouring pools in a chain of ponds.

8. Designing platypus-friendly lakes and ponds

Platypus will demonstrably make use of a wide range of manmade off-stream water bodies, including dams developed for irrigation or stock and domestic usage, flood retarding basins, siltation or filtration ponds, and ornamental lakes associated with residential, recreational and industrial developments. Accordingly, development or refurbishment of such water bodies can provide excellent opportunities to create additional platypus habitat. For example, the Hull Road Retarding Basins, near Lilydale – a joint-project by Melbourne Water and the Australian Platypus Conservancy to design a platypus-friendly wetlands  – were occupied by platypus within two years of construction.

In broad terms, the animals are most likely to find and regularly use an off-stream dam, lake or wetland if the following conditions apply:

  • The manmade water body is located relatively close to a creek or river known to be occupied by platypus (in general terms, within 100 metres or ideally less) and is sometimes (ideally always) linked to the creek or river via surface water.
  • The manmade water body supports substantial populations of edible aquatic invertebrates, particularly aquatic insects. In practice, this will rely on livestock being excluded from the banks and herbicides and pesticides and other agricultural chemicals not being deployed in the immediate vicinity.

What can be done to protect platypus:

  • To provide protection from predators and ensure that the water remains reasonably cool (to maintain appropriate conditions for a range of aquatic invertebrates), pools should ideally retain water at a minimum depth of 1-4 metres. To help protect platypus from foxes and other predators, the perimeter of the pool should slope steeply downward unless dense emergent aquatic vegetation (such as reeds) is to be established around the edge.
  • To provide habitat for platypus burrows, some of the pool’s perimeter should ideally be bounded by a reasonably steep and well-consolidated earthen bank rising at least 1 metre above the water.
  • Overhanging shrubby vegetation should be encouraged to grow on the bank surrounding the pool to improve habitat quality and provide additional cover from predators. For the same reasons, shrubby vegetation should be encouraged to develop along the route taken by surface water overflowing from the manmade lake or pond to a nearby stream or river (including seasonally dry ditches or channels).
  • Adding some items of large woody debris to an artificial water body (in the form of logs or large branches) is predicted to improve habitat diversity both for platypus and their prey and is therefore encouraged.

For advice regarding the development of pedestrian paths, viewing platforms or lighting, see 10, Walking tracks, viewing platforms, bridges and street lighting. For information relating to the design of culverts and pipes or the development of weir walls and related structures see 11, Culverts, pipes, gates and grilles and 12, Weir walls and drop structures.

9. Use of heavy machinery along the banks and channel

Based on radio-tracking studies which investigated how platypus respond when heavy equipment such as excavators and tip trucks are used to reconfigure the banks and channel of streams, platypus normally continue to inhabit the area while works are in progress. However, severe and extensive channel disturbance can displace the animals temporarily, presumably due to reduced availability of food.

Special consideration also needs to be given to the requirements of females with dependent young in the months when juveniles are confined to the nesting burrow (extending roughly from September to February in Victoria and New South Wales). Mothers cannot move their young from one burrow to another in this period and so are effectively tied to the area. It follows that reducing the local food supply through major habitat disruption may compromise their survival as well as that of their offspring. By the same token, digging or substantially compacting the banks at the site of a nesting burrow is likely to be fatal to the entire family.

What can be done to protect platypus:

  • If a water body is known to support a breeding platypus population, capital works programs which involve reconfiguring the banks or channel should ideally be scheduled outside the period when dependent juveniles are present in burrows (see above).
  • To reduce damage to platypus burrows, activities which involve excavating or driving over banks with heavy machinery should be minimised at all times of year, particularly on those parts of the bank located within roughly 10 metres of the waters edge.
  • To avoid disturbing platypus when the animals are active, work activities should only be scheduled during daylight hours.
  • Great care should be taken to keep loose soil from moving from the banks to the channel while works are underway, and areas of bare or disturbed soil should be replanted as soon as possible with trees and understorey plants once works are completed.
  • Chemicals or litter associated with work activities should never be allowed to enter the water.
  • To maintain natural foraging substrates for platypus, concrete should not be substantially used as a binding agent along the channel or banks. Similarly, gabion baskets should not be extensively employed to stabilise banks if practical alternatives are available.
  • A contingency plan for dealing with any platypus that may be accidentally injured or displaced during work activities should be formulated and distributed to project staff.

10. Walking tracks, viewing platforms, bridges and street lighting

Based on information obtained in the course of radio-tracking studies, platypus mortality may increase very substantially following the development of a walking track which improves predator access to shallow stream margins.

By the same token, it is believed that platypus are mainly active at night to reduce the chance they are detected by predators. Besides making platypus more visible to animals that want to eat them, the presence of bright artificial lights near a stream or river may reduce the platypus food supply by inappropriately attracting aquatic insects as these emerge at dusk to breed and lay eggs.

What can be done to protect platypus:

  • In places where platypus are likely to occur, walking tracks should be located a substantial distance (ideally 30 metres or more) from sections of creek where the average depth is less than 0.3 metre and/or average width is less than 3 metres, on either a regular or seasonal basis.
  • To reduce predator access and discourage the development of ad hoc human trails down to the water, pedestrian bridges and viewing platforms should be located at sites where banks are relatively steep and water is reliably deep.
  • Maintain adequate vegetation between a walking track and the banks of a stream or river, ideally including a substantial amount of cover provided by leafy shrubs or the equivalent overhanging the water. As the absolute minimum, an unmown strip of low- to medium-growing plants (at least 4 m wide in the case of relatively small/shallow streams and 2 m wide in the case of deeper/wider rivers) interspersed with substantial clumps of taller overhanging shrubs should be encouraged to grow on the banks to help deter predators and provide places for platypus to hide.
  • Street lights, security lights or the equivalent that are located within 100 metres of a natural water body should be designed to minimise the amount of artificial illumination directed towards the water, and ideally fitted with low-pressure sodium globes producing relatively low amounts of insect-attracting blue and ultraviolet light.

11. Culverts, pipes, gates and grilles

Given that platypus spend a large proportion of their time in a burrow, it is not surprising that they are willing to travel through pipes and culverts of considerable length. For example, radio-tagged platypus have been found to travel routinely through a 45-metre-long concrete culvert (1.3 metres in diameter) carrying creek water through an embankment.

However, problems can arise if a culverts design forces the animals to leave the safety of the water in order to continue traveling upstream or downstream. In such circumstances, it is by no means uncommon for animals to be run over by a car or killed by a fox or other predator. By the same token, although platypus will enter PVC pipes that are as narrow as 10 centimetres in diameter, they are apparently unable to back up or turn around in such a confined space and hence are liable to die if the far end is blocked (for example, by a recently closed valve). Cases are also known where platypus have drowned after becoming wedged in narrow openings in irrigation control gates or overlapping wire mesh panels placed in the channel to catch leaves.

What can be done to protect platypus:

  • Pipes and culverts located along a natural waterway or manmade channel that is used by platypus – or that carry water from such a waterway to an off-stream storage – should have a minimum internal diameter of 0.3 metre to ensure they can be negotiated safely by a platypus.
  • To enable platypus to safely negotiate grilles or mesh barriers, these structures should be designed with grid spacings or apertures of 12 centimetres or more. Conversely, barriers meant to exclude platypus should be constructed of solid materials or have grid spacings or apertures of 3 centimetres or less. (Studies carried out by Dr Tom Grant have confirmed that platypus weighing up to one kilogram – i.e. a large proportion of adult females – can easily pass through a rigid 55 mm grid, and small juveniles can presumably pass through even narrower gaps.)
  • To avoid forcing platypus to leave the channel, pipes and culverts conveying water along a natural waterway or soil-lined channel should not protrude from (or substantially overhang) the surrounding substrate. Similarly, culvert designs that frequently constrict stream flows and may therefore trigger platypus avoidance behaviour (due to increased water velocity) should not be adopted.

12. Weir walls and drop structures

Platypus generally find it difficult or impossible to climb up or down vertical or near-vertical concrete or metal surfaces, particularly if large volumes of water cascade down the surface. Accordingly, weir walls and drop structures often interfere with platypus freely traveling along the length of streams or rivers. As in the case of culverts, platypus can exit the channel and walk around otherwise impassable barriers. However, leaving the water also exposes them to increased risks of being killed (see 11, Culverts, pipes, gates and grilles).

What can be done to protect platypus:

  • Support the development of fish ladders or the equivalent to provide a relatively safe route for platypus to negotiate dam and weir walls.
  • If a weir cannot realistically be retro-fitted with a fish ladder, consider whether it might be possible to provide platypus with additional protective cover (in the form of dense shrubby vegetation) when they’re forced to travel across land to move past the barrier.

13. Pumps and small-scale hydro-power generators

A surprisingly high proportion (5%) of all platypus mortalities reported to the APC from 1989 to 2009 where the cause of death could be reliably assigned occurred after animals were sucked into irrigation pumps or (in one case) a mini-hydroelectric generator. Small and inexperienced juveniles appear to be particularly likely to die in this manner, due in part to the fact that pump sheds tend to be located on elevated banks which in some places provide the best available habitat for platypus nesting burrows.

What can be done to protect platypus:

To prevent platypus and other aquatic wildlife from being sucked into (or against) water pumps or water-powered generators, a mesh cover or equivalent barrier should be fitted at an appropriate distance around all intake points.

14. Promoting awareness of platypus conservation needs

Most Australians are aware that the platypus is one of the world’s most unusual animals. Ironically, this recognition of the species’ iconic stature tends to foster the misconception that platypus are only found in remote, pristine areas.

For platypus to be conserved successfully, it is important that people develop a realistic understanding of where the animals occur and how they are affected by human activities.

What can be done to protect platypus:

  • Catchment Management Authorities, local councils and wildlife agencies should feature the platypus in community education campaigns designed to heighten awareness of issues such as litter control, pet management and responsible fishing practices.
  • Consideration should be given to establishing Platypus Conservation Zones where this will assist the survival of threatened populations. Such zones could incorporate special signage and, if required, restrictions on fishing and access of pets to riparian areas. In particular, planning authorities should consider placing a ban on owning dogs and cats as a condition of approval of new housing estates located within 100 metres of creeks supporting a known threatened platypus population.