Radio-tracking studies have confirmed that a platypus will normally remain with its established home range while work is in progress to reconfigure the banks or channel. However, severe and extensive disturbance by excavators or other heavy equipment can cause animals to shift their activity temporarily to other parts of the channel, returning home when the local aquatic ecosystem has had a chance to recover.
Human activities that involve digging up or compacting the banks can also damage or destroy platypus burrows. It is rarely feasible to identify the precise location of active platypus burrows: entrances are generally quite small (just large enough for a platypus to enter) and in most cases are very well hidden below stably undercut banks or overhanging vegetation. Some entrances are even located underwater. Although platypus burrows can measure up to 30 and possibly even 55 metres in length, most are less than 10 metres long when measured from the edge of the bank to the burrow chamber.
Special consideration needs to be given to the requirements of females with dependent young in the months when juveniles are confined to the nesting burrow. The critical period extends roughly from September to February in Victoria and New South Wales, with breeding believed to start a few weeks earlier in Queensland and up to two months later in Tasmania. Mothers cannot move their offspring 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, excavating 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 the platypus?
- If a water body is known to support a breeding platypus population, works programs which involve reconfiguring the banks or channel should be scheduled well outside the period when dependent juveniles are likely to be present in burrows.
- To reduce damage to platypus burrows, activities which involve excavating or driving heavy machinery across banks should be minimised throughout the year, particularly within about 10-15 metres of the water’s edge.
- Appropriate and vigorous action should be taken to minimise the risk that bank or channel erosion may occur at work sites. Areas of bare or disturbed soil should be revegetated as soon as possible once works are completed, and the soil surface stabilised effectively using appropriate matting or netting until plants are well established.
- Chemicals or rubbish associated with work activities should never be allowed to contaminate the banks or water.
- To maintain natural foraging substrates for platypus, concrete should not be used as an extensive binding agent along the channel or banks. Similarly, gabion baskets should not be employed to stabilise banks if practical alternatives are available.
- Use caution whenever excavating the banks of natural or manmade water bodies and ensure that a contingency plan is in place to deal with any platypus that may be accidentally dug up (for example, see Contingency plans for platypus – capital works programs).