The marsupial was found draped in a shawl with a cap and a bottle of the Greek spirit ouzo propped under its arm in Plenty Road, Mernda, last month.

Department of Environment, Land, Water and Planning investigators said the kangaroo had been shot at least three times before being posed.

Senior investigator Mike Sverns released a picture of the kangaroo on Tuesday in the hope that more witnesses would come forward.

"It would have taken some time to stage the kangaroo in that position on the side of the road and we are certain that someone would have seen something, given the public area and traffic flow of this main road," he said.

"This is appalling and immoral behaviour and we are urging anyone with information to come forward." 

The shocking sight was reported to wildlife rescuers by a woman, who spotted it on her way to work at 7.30am on May 17. 

Mr Sverns said there were two other witnesses: a man who drove past the kangaroo at 7.15am, and another who saw a sedan parked in the same location before sunrise at 6am.

The location is in open farmland, near the intersection of Arthurs Creek and Plenty roads.

Rigor mortis was only just setting in, suggesting the kangaroo had been shot that morning or the night before.

Mr Sverns said Environment Department staff were called to cases of animal cruelty regularly, but instances normally occurred at the weekend.

This was a Wednesday morning and Plenty Road was full of people on their way to work and school.

Investigators suspect the kangaroo was killed in a different location, then brought to its final, undignified resting place.

The animal had been shot three times in the chest with a small-calibre firearm commonly owned by farmers and recreational shooters.

Mr Sverns believes whoever left the kangaroo behind had spent at least 30 minutes there, first securing it to the chair with wire then dressing it in a leopard-print shawl and a frilly purse.

Gaffer tape, presumed to be from an initial attempt to secure the kangaroo, was found discarded at the scene.

All items will undergo forensic testing.

The penalty for killing protected wildlife is up to $36,500 and as much as two years' jail.

Mr Sverns said cruelty to wildlife was not an unusual occurrence.

"We're seeing an ongoing trend where people are directing misconduct towards native animals, for some reason," he said.

Anyone with information can call Crime Stoppers on (1800) 333 000.