I’ve been visiting Carnarvon Gorge (part of Carnarvon National Park), on work trips as part of my role with the Queensland Parks and Wildlife Service, for about 15 years. In all that time I’ve never just sat by Carnarvon Creek and taken a determined look for one of the park’s most iconic creatures — platypus.

I’ve seen them briefly while walking creek-side at Carnarvon, but it’s never been much more than a glimpse. My childhood memories of platypus are mixed. As a young lad, standing fairly close to David Fleay during one of his platypus shows at his West Burleigh reserve, I marvelled at the mysterious creature that moved into view in the concrete display tank. Unfortunately, the memory is scarred by the recollection of either my brother or I accidentally kicking an empty coke bottle across the floor, not long after Mr Fleay reminded all of the utmost need for quiet and even no finger pointing. The scornful glance of the legendary naturalist was memorable.

So, on another recent quick work trip to Carnarvon, I headed down to the creek about 4.30am to see if these things really existed. If lucky, I’d get to see one, and maybe I could capture a photograph or two of the mysterious beasties. I had no hope for anything too successful photo-wise, as I’d no intention of using a flash on such shy creatures and platypus are well known for not being photogenic in the wild (like any sensible animal).

I took up a spot above the bank and sat quietly in the grass, scanning the slowly brightening waters of this marvellous creek.

Carnarvon Creek is a magical place. The water always flows, part of a process that has endlessly and relentlessly carved through basalt and sandstone to create one of Australia’s most wondrous gorges.

Multi-hued and sun-dappled creekside vegetation, as well as towering sandstone cliffs and woodland perched high above the gorge floor, are reflected in the creek’s waters. The icing on the cake is the array of animals, of which surely the platypus is the most elusive and mysterious, that call this creek home.

After a short time just sitting, a movement caught my eye. A wake was spreading out behind a moving brown lump. It was a platypus, motoring across the surface of the creek. I held my breath and tried not to kick any coke bottles.

Over the next hour, and again the next morning with a colleague (Raelene Neilson, some of whose photos are included below), I followed the progress of two platypus as they worked their way around a large, still part of the creek, not far from the visitor area.

A platypus morning seems to be spent drifting and motoring about like a tiny barge, interspersed with frequent diving and searching in the sediment for yabbies and other food. A trail of bubbles tells of a platypus searching for food on the bottom of the creek.

Carnarvon Creek reflections (click on image for closer look)

It’s a serene body of water — usually. However, as the rangers working here know, this quietly flowing creek has a wild side. Every now and then, floodwaters rage down the gorge system in an immense, turbulent  show of power, tearing out creek-side trees and rolling huge boulders.

How do platypus survive such times?

Surely some of them are killed. Perhaps they are able to wait things out in their burrows, but it’s hard to imagine how they’d do this when the floodwaters can last for days. Or perhaps they sense the approaching floodwaters and quietly head away from the creek, returning when water levels  subside.

We have very few photographs of Carnarvon platypus on our QPWS files. One of them bears the caption “After the floods, the platypus come out”. I’d assume that this platypus has been photographed in the calmer creek waters not long after a flood.

Tom Grant, in The Platypus, a Unique Mammal recounts  that in the first five years of a 20-year study of platypus in the upper Shoalhaven River in New South Wales, seven floods occurred, all of which changed the river from its normal series of deep pools with connecting rapids into a raging mass of brown water with no distinction between pool and rapid. Their study found that while some platypus are killed, most were not even displaced from their home ranges by the floods.

As platypus have occupied the rivers of Australia for at least 50,000 years, they have presumably evolved strategies to cope with flooding, However, it is still unknown how they ride out floods. Early naturalists suggested that they occupy rabbit burrows and hollow logs away from the river, returning later. Some recent radio-tracking work has shown that platypus of the Goulburn River avoid high flows associated with the release of water from the Eildon Weir for irrigation used a backwater area to avoid the faster-flowing water. They even found that the animals would still enter the river to feed, paddling against the current. However, it would be hard to imagine them being able to feed easily during the raging Carnarvon Creek floods, at least during the wilder periods of flooding.

The Australian Platypus Conservancy reports how damage to creek banks and burrows happens with floods:

In theory, depending on their magnitude and duration, floods could have either a positive or negative impact on platypus populations. The effect of minor flooding is likely to be relatively benign and could even improve the quality of platypus habitat, for example by flushing accumulated silt from pools.

By comparison, severe flooding is much more likely to affect platypus populations adversely. The animals may drown, contract pneumonia after inhaling water, or be swept downstream and have to find their way back through unfamiliar terrain. Their burrows may also be inundated for a substantial period of time and food supplies badly depleted due to invertebrates being washed away.

Flooding can also degrade the quality of platypus habitat if it causes banks to erode, pools to become filled with sediment, or in-stream woody habitat (logs and branches) to be deposited on land as flood waters recede.

A study conducted by the Australian Platypus Conservancy in mid-2008 examined how platypus populations in four Gippsland rivers were faring approximately 9–11 months after substantial floods occurred. In each case, flooding peaked at an estimated flow rate of more than 10,000 megalitres/day. In brief, the severity of flood-related habitat damage was inversely related to platypus population density and reproductive success: the river suffering the greatest damage had the lowest numbers of platypus and the smallest proportion of juveniles (none), whereas the least damaged area had the highest density of platypus and the largest proportion of juveniles. It was concluded that flood-related impacts can have a measurable adverse effect on platypus populations, particularly when (as was true in this study) the vegetation on adjoining slopes has recently been damaged by wildfire.

The fact that juvenile platypus are weaker and less accomplished swimmers than older animals suggests that they may be more likely to be killed by floods, particularly if these occur around the time that juveniles first emerge from the nesting burrow in summer. This is supported by the results of live-trapping surveys carried out in the Melbourne area after more than 120 millimetres of rain fell on the city in less than 24 hours in early February 2005 (the highest one-day total since weather records were first kept in 1855). The mean juvenile capture rate from February to June 2005 was less than 10% of the corresponding mean capture rate from 2001-2004. In contrast, the capture rate for adults and subadults occupying the same five water bodies from February to June 2005 was actually slightly higher than the corresponding mean capture rate from 2001–2004.

In his book Paradoxical Platypus — Hobnobbing with Duckbills, David Fleay describes the effects of floods on young platypus in south-eastern Queensland:

As a spin-off from my appointment as weekly Nature Columnist (1952-80) to the Brisbane Courier Mail, I was in touch with most platypus happenings in south-eastern Queensland. This proved not only invaluable but very instructive.

So in way or another, numerous duckbills passed through our hands, particularly those babes rescued from peril at the generally early south-eastern Queensland nest-leaving period (late December to early February).

At least four such inexperienced juveniles were actually flotsam in the mile–distant Pacific Ocean at the tail-end of cyclones. Naturally, sudden savage flooding takes victims by surprise and bears the unwary, willy-nilly into the sea.

Times of flood must bring turmoil to the quiet morning ritual that I was fortunate to observe at Carnarvon Creek.

While there is some evidence that platypus may be adapted to survive a natural event like a flood, the effects of humans on our waterways is far more detrimental to these mammals. Having survived hunting for pelts in the 19th century, platypus now face a far greater human threat — our impact on waterways due to agriculture, forestry, dam construction, mining and industrial activities. Illegal and inappropriate fishing practices, particularly the use of nets in creeks, also kill platypus. The health of platypus populations is inextricably linked to the health of our waterways, and our activities around these river systems. How we treat our creeks and rivers will determine how well platypus survive into the future.

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I greatly enjoyed my brief time watching these unusual mammals. They were full of energy and life as they worked the creek in search of food, sometimes stopping to drift and seemingly take in what was going on around them.

The sense of privilege and wonder I felt while sitting next to that serene creek lingered. Back at my work desk, I paused from the cubicle chaos to think of the morning calm of Carnarvon Creek and its marvellous residents. I really hope they’ll be messing about there forever.

 

Links:

• Carnarvon Gorge, QPWS.
• Platypus at Takarakka.
• Best day walks at Carnarvon Gorge.
• The David Fleay story
• Ray Wilson Carnarvon photo blog.
• A Platypus Quest: Six Mile Creek discoveries.
• The Australian Platypus Conservancy.