Authorities are investigating the discovery of a deceased dugong which had been dismembered at the Cape Pallarenda Conservation Park.
A resident alerted Queensland Parks and Wildlife about the dead mammal, which is a protected species, on Wednesday morning.
QPWS said it believed the dugong was killed and dismembered at the site, where several mutilated sharks were also found.
It is an offence to take a protected species.
The discovery outraged a local conservationist, who said the "horrible" behaviour was unheard of in the Townsville region.
Simon Cheers from the North Queensland Conservation Council said dugongs desperately needed protection.
"We really need to look after these species," he said.
"Dugongs play an extremely important role in the ecology of our costal environments.
"We need to ensure that they stay persistent in the environment for many years to come."
Mr Cheers said he believed it was widely understood that dugongs were protected.
"I think people are aware in Queensland about the limited number of dugongs and how the population has decreased over the last 50 or so years," he said.
"If it proves to be the case that these dugongs and sharks have actually been attacked by a human, it's incredibly disappointing.
"These animals have just as much right to be alive as we do.
"It's just not appropriate at all."
Anyone with information is urged to contact Queensland Parks and Wildlife Service on 1300 130 372.
