Household litter is putting the lives of platypus at risk with researchers regularly catching platypus entangled in items such as hair ties, plastic rings and fishing lines.
While entanglement is more common in platypus living closer to urban area, those caught during surveys of regional platypus populations have also been found caught up in litter.
Australian Platypus Conservancy director Geoff Williams said up to one in 25 platypus living in some waterways are entangled in one or more items of rubbish.
In recent years, an adult male platypus in the Moorabool River at Morrisons was found with an elastic band around his neck, while a juvenile female in Mount Emu Creek at Skipton had a small plastic ring, probably the seal off a milk bottle, around its neck.
"That one would almost certainly have died if we had not caught her during a live-trapping survey and been able to remove it," Mr Williams said.
"That platypus at Skipton was one of 14 individuals identified in surveys there, making it a seven per cent entanglement rate and putting it in the same ball park as city waterways."
Platypus are known to live in several rivers north and south of Ballarat and throughout the Central Highlands region, with one of the closest sightings to the city in the Yarrowee River at Garibaldi several years ago.
The population at Skipton has been monitored for many years, and in recent years platypus have also been seen in the Ballarat region in Birch's Creek at Smeaton, Creswick Creek at Clunes, St George's Lake in Creswick, the Leigh River around Grenville, Meredith and Shelford, and the Moorabool River.
The Australian Platypus Conservancy, which regularly carries out live trapping to survey platypus numbers, recently published a paper in the journal Australian Mammalogy analysing patterns of platypus litter entanglement based on 30 years of fieldwork.
Items recovered from animals that died or were severely injured due to entanglement included elastic hair-ties, fishing line, a hospital identification wristband, an engine gasket and plastic ring seals from milk bottles and food jars.
Mr Williams said while there had been little live-trapping in the Ballarat and central highlands regions, the litter problem was everywhere.
"We haven't done that much live-trapping in the area so the number of actual examples of platypus with litter is fairly limited. If we had sampled more waterways, I've no doubt that litter entanglement would have been recorded in virtually all rivers and creek, especially those that run through regional towns."
In some suburban waterways up to one in seven animals was entangled.
More adult female platypus were found entangled than adult males, which could impact breeding levels.
And while the frequency of platypus litter entanglement was lower in rural creeks and rivers, it included a higher proportion of more lethal materials such as discarded fishing line.
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Senior conservation biologist Melody Serena said litter entanglement was a concern for platypus because they search for food at the bottom of waterways where rubbish accumulates. And the platypus's front foot was incapable of pulling off an entangling item, so once litter slipped around an animal's neck or chest it tended to stay there and rub through skin and muscle skin and muscle, eventually causing serious injuries and even death.
"Human behaviour is the key to solving this issue to keep platypus safe," Dr Serena said.
She urged everyone to cut through all discarded rings or loops, especially anything made of plastic, rubber or metal, before disposing of it in recycling, never discard fishing line, and to always pick up litter that could entangle a platypus because small items like hair ties wash in to stormwater drains and end up in creeks.
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