Three platypuses in five weeks have been found dead in the NSW-Victorian border town of Albury, concerning wildlife officials.
A Wildlife Information Rescue and Education Service spokeswoman says the deaths are a mystery.
"They're quite elusive and they're also incredibly hard to catch, so we're really nonplussed about how anyone could have even captured them to begin with let alone harm them."
The platypuses were discovered decapitated which is suspected to have been caused by a sharp object.
"These animals appear to have been deliberately killed in a despicable act of cruelty to one of Australia's most loved animals."
Penalties for being convicted of harming native animals can be fines as high as $11,000 or even six months in prison.