The development of infrastructure that leads to increased human activity or nocturnal illumination near waterways has the potential to adversely affect platypus foraging.
For example, although these animals rarely appear to react to the presence of a person or two sitting quietly on the banks, the arrival of numerous chattering humans can cause a foraging platypus to move away to a less threatening site (Pete Walsh, pers. comm.).
Research has also shown that platypus mortality risk can increase following construction of a walking track that facilitates predator access to the margins of a shallow creek (mortalities described in Serena 1994).
Recent studies have shown that bright artificial lighting at night can affect activity patterns of both aquatic insects emerging from the water to breed and their predators (e.g. Parkinson et al. 2020), and may also exacerbate negative impacts of stressors such as noise or abnormally high water temperatures on aquatic fauna (reviewed in Ganguly and Candolin 2023). Although relevant research has not yet been conducted to examine how artificial lighting affects platypus foraging success or mortality risk, it wouldn’t be surprising if increased light levels makes it easier for for predators such as foxes to detect and pursue a platypus. Artificial lighting may also potentially reduce the platypus’s food supply by inappropriately attracting aquatic insects away from the water as they emerge at dusk to breed.
What can be done to protect the platypus?
- Walking tracks should normally be located at least 30 metres from creeks, rivers or lakes where platypus activity may occur (Le Feuvre et al. 2018). To reduce predation risk and discourage the development of informal human paths down to the water, bridges or viewing points that are located near the water should be placed at sites where the water is reliably deep and banks are steep.
- It is essential that unmown grasses and/or taller shrubs (particularly plants overhanging the water) are encouraged to grow on the banks of streams and rivers – both to reduce predator activity near the water and to provide platypus (and other wildlife) with cover and places to hide if a predator does appear. If necessary, post signs to warn pedestrians that snakes may be active in the vicinity.
- Street lights, security lights or the equivalent 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 be fitted with low-pressure sodium light globes (or bulbs) producing relatively little insect-attracting short-wavelength (blue and ultraviolet) illumination. By comparison, LED light globes typically generate much higher amounts of short-wavelength illumination (Longcore et al. 2015).
- Wildlife viewing platforms located near platypus habitats should be designed to minimise the likelihood that a platypus feeding in the vicinity will be disturbed by human noise or activity.
Photo: APC
LITERATURE CITED
Ganguly A and Candolin U (2023) Impact of light pollution on aquatic invertebrates: behavioural responss and ecological consequences. Behavioral Ecology and Sociobiology 77, 104.
Le Feuvre M, Sutton F and Malony C (2018) Riparian setback widths: a review of recommendations for guidelines. Report to Melbourne Water by Ecology Australia: Fairfield VIC.
Longcore T, Aldern HL, Eggers JF, Flores S, Franco L, Hirshfield-Yamanishi E, Petrinec LN, Yan WA and Barroso AM (2015) Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods. Philosophical Transactions of the Royal Society B, 20140125.
Parkinson E, Lawson J and Tiegs SD (2020) Artificial light at night at the terrestrial-aquatic interface: effects on predators and fluxes of insect prey. PLoS ONE 15, e0240138.
Serena M (1994) Use of time and space by platyus (Ornithorhynchus anatinus: Monotremata) along a Victorian stream. Journal of Zoology 232, 117-131.