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August is \u2018Platypus Month\u2019 \u2013 and it\u2019s the best time of the year to spot them in the wild. Photo: Richard Taylor, Waterwatch.<\/p>\n
The ACT\u2019s waterways are becoming increasingly cleaner, leading to growing populations of their apex predators, according to local volunteer group \u2018Waterwatch\u2019.<\/p>\n
The platypus and rakali (or water rat) sit at the top of the food chain in the local waterway ecosystem, mainly feeding on waterbugs. But if rivers become too choked with sediment, water bugs can\u2019t survive and bring predator numbers down with them.<\/p>\n
It\u2019s happened in Cooma Creek.<\/p>\n
\u201cWe\u2019ve seen decreases particularly in the Cooma Creek and Scottsdale Reserve sites on the Murrumbidgee after the 2020 bushfires, when a lot of sediment was moving through the river and filling up a lot of the habitat spots,\u201d Waterwatch facilitator Daniel Harris-Pascal says.<\/p>\n
\u201cWe\u2019re finally seeing the impact of that lessen as we move in time away from the fire.\u201d<\/p>\n
Waterwatch runs Platypus Month every August, inviting Canberrans to get out and spot as many platypuses as they can in the wild.<\/p>\n
Since 2013, with funding from the ACT Government and Icon Water, it has surveyed eight sites in the ACT and surrounding region to ascertain how both this species and the water rat are doing.<\/p>\n
Last August, about 700 people took part in the survey, either reporting sightings through the \u2018Platty and Ratty Portal\u2019 on the Waterwatch website or taking part in group ventures at dawn and dusk.<\/p>\n
A total of 29 individual platypus and 19 water rats were detected across eight survey sites \u2013 healthy numbers for both species.<\/p>\n
\u201cBroadly, we see about 25 platypuses in the surveys and about 20 rakali \u2013 we have seen rakali numbers increase somewhat, and for the most part, it looks like platypus populations are stable,\u201d Mr Harris-Pascal says.<\/p>\n
\u201cObviously, in a drought year, there are fewer platypus around and surviving, and then in wetter or more abundant years, they\u2019re back. But the main limitation for platypus, probably in our region, is habitat availability. So, it\u2019s just about having space and then the water bugs in the water to support those populations.\u201d<\/p>\n<\/p>\n
A female platypus will lay between one and three eggs at a time, and by late summer, there\u2019ll be a \u201cflurry of sightings\u201d as the young not only leave the nest but are pushed out of the area by the dominant male.<\/p>\n
\u201cThey\u2019re definitely territorial. In our region, one platypus\u2019s whole range could be about 7 km.\u201d<\/p>\n
Combined with rakali, which are largely scavengers, Mr Harris-Pascal says the recent numbers come down to \u201ca lot of work in the ACT to improve waterways\u201d.<\/p>\n
\u201cIt\u2019s one of many types of reading that we do because platypus and rakali are top-order predators, and so by checking their numbers, we can kind of \u2013 by proxy \u2013 get an understanding of the health of the underlying ecosystem.\u201d<\/p>\n
As Waterwatch kicks off its 12th round of surveys this August, the organisation is again calling for volunteers to help.<\/p>\n
Queanbeyan River is always a hotspot due to its water quality, fed by the Tinderry and Googong catchments, rather than other rivers that pass through urban areas.<\/p>\n
\u201cObviously, with the Murrumbidgee, there\u2019s not quite enough flow in the river and it also moves through Cooma and Tuggeranong, and all of that, so Queanbeyan\u2019s got this Goldilocks thing where it\u2019s an urban river, but the catchment for the river is not,\u201d Mr Harris-Pascal says.<\/p>\n
\u201cWe\u2019re keen to see that persist, particularly as Googong and those areas grow.\u201d<\/p>\n
Waterwatch would also like to see more sightings in three key areas, including Ginninderra Creek below Lake Ginninderra, the Gudgenby River in Namadgi National Park, and the Yass River and its tributaries.<\/p>\n
\u201cNo confirmed sightings of platypus have been received in this section of the Ginninderra Creek since the lake was built in the 1980s,\u201d the Waterwatch website says.<\/p>\n
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Scouring waterways for the elusive platypus. Photo: Waterwatch.<\/p>\n
It\u2019s a similar story for the Yass River, with only a handful of \u201canecdotal sightings\u201d.<\/p>\n
The Gudgenby River catchment was historically home to platypus, but sightings have dried to zero since the 2020 bushfires, which devastated the area.<\/p>\n
\u201cThe main river and its tributaries in the top half of the catchment (within Namadgi National Park), such as Bogong Creek, Rendezvous Creek and Dry Creek, would be of interest. Also, the lower section of the Orroral River (top section is still off limits due to fire damage) has limited historical data and sightings here would be welcomed.\u201d<\/p>\n