The Tumut office of the National Parks and Wildlife Service (NPWS) is leading the investigation into three platypi found decapitated in Albury.
NPWS spokesperson Sarah Scroope said the rarely seen creatures had died at human hands.
“These animals appear to have been deliberately killed in a despicable act of cruelty to one of Australia’s most loved animals,” she said.
“NPWS is working with Albury City Council and WIRES to look into these incidents.”
The Australian arm of Humane Society International is also offering a $5000 reward for information about who killed the platypi, but so far no arrests have been made.
Ms Scroope said those responsible would face consequences when, or if, they are caught.
“It is an offence under the National Parks and Wildlife Act to harm native animals and penalties include a fine of up to $11,000 and/or six months imprisonment,” she said.
“We are calling on anyone with information to please contact NPWS Tumut office on 6947 7025.”
The animals were found in the Albury Botanic Gardens, two with their heads cut off by a sharp object.
Wildlife Information Rescue and Education Service Murray River secretary Hazel Cook said it was concerning someone had even been able to catch the three separate platypi, that were found in the park over a period of five weeks.
“We have no idea why anyone would do that, especially to something as gentle as a platypus,” she said.
“There definitely was no fox involved – that’s the first thing we thought everyone would think, but we took it to a local vet and had them check it out.
“You could see where it was cut, where the spine was cut. You can actually see where they’ve tried to cut into the vertebrae.”
Ms Cook believes the platypi were trapped and killed elsewhere and placed in the Botanic Gardens to disturb the public.
The platypus is a protected species.