Ellie-May had been missing for two days before the grim discovery was made by a member of the public in Lincoln Drive, Cannock.
The RSPCA has launched an investigation to find out whether the pet has been killed by a human or a wild animal.
The owner of the 18-month-old black and white cat, Brenda Hearndon, said the news of her last moments was "awful".
The 74-year-old said: "I have had Ellie-May since she was dumped 10 months ago with 12 kittens and she worked so hard bringing these kittens up.
"She was a very timid cat but she was affectionate towards me.
"It is so sad because she was just starting to enjoy life, going outside and doing what cats like to do, but now something like this has happened and it is awful."
RSPCA inspector Kate Levesley said: "We do not know for certain how Ellie-May died, whether it was by the hands of a cruel human being or whether she died naturally and had started to be scavenged by wild animals.
"However we cannot rule anything out. If this was done deliberately, it does not bear thinking about how terrified Ellie-May may have been in her last moments."
Anyone with information is urged to come forward.

The security breach by Norfolk County Council came to light in April 2014 when the cabinet was bought and the social work case files were found.
The Information Commissioner's Office (ICO) said the documents included information relating to seven children.
The ICO said the council had "no good reason" for breaching confidentiality.
More news from Norfolk
The council apologised for the data breach and said it had tightened procedures.
Steve Eckersley, ICO head of enforcement, said: "The council had disposed of some furniture as part of an office move but had failed to ensure that the cabinets were empty before disposal.
"Councils have a duty to look after any personal information they hold, all the more so when highly sensitive information is concerned - in particular about adults and children in vulnerable circumstances.
"For no good reason Norfolk County Council appears to have overlooked the need to ensure it had robust measures in place to protect this information.
"It should have had a written procedure in place which made it clear that any storage items removed from the office which may have contained personal were thoroughly checked before disposal."
The ICO added that having the "appropriate staff and procedures in place is key to ensuring councils look after personal information properly".
Simon George, executive director for finance and commercial services at the council, said: "We want to reassure residents that we have robust data protection procedures and have tightened practice in the light of the case published today.
"As a council we take data protection very seriously and we are very sorry that our practice fell short on this occasion.
"In the three years since this occurred, we have taken strong and effective action to ensure it is not repeated."
The county council was fined Â£80,000 in February 2012 by the ICO after a confidential social worker report was sent to the wrong address.

Ben Gilkes, 25, of Stratford Road, Sparkhill, will appear at Birmingham Magistrates Court, West Midlands Police said.
A man was arrested on Friday after the child was taken to Birmingham Children's Hospital with serious head injuries, police said.
The baby remains seriously ill since the assault in Hall Green on Friday, they added.
The body of a cat missing its head and tail has been found in a Staffordshire garden.
[NEXT_CONCEPT]
A council has been fined Â£60,000 for leaving confidential files about vulnerable children in a cabinet which was sent to a second-hand shop.
[NEXT_CONCEPT]
A man is due in court charged with an assault on a four-week-old baby boy.