Police believe the statue was stolen from the museum in Gold Creek, Nicholls, on Tuesday night sometime between 10.30pm on November 11 and 1am on November 12.

A group of three or four offenders are believed to be responsible for trespassing on the property, before stealing and vandalising the model dinosaur worth about $1200.

ACT police found the model, lying damaged in a local park, and suspect the dinosaur have been an end-of-year school stunt.

National Dinosaur Museum manager Richard Mancuso said he was "frustrated" the museum had been the subject of yet another prehistoric practical joke in his three years in the job.

As recently as November last year, vandals caused about $2500 damage when they pushed a parasaurolophus dinosaur statue against nearby rocks and and removed parts from two velociraptor statues in a late night incident.

Earlier, after a three-day hunt in March 2013, a fiberglass Utahraptor statue was found after it was stolen as part of a birthday prank.

"In the past when it occurred it just appeared to be tied up with a juvenile prank. I suppose that some people think it's funny, most of the time it is related to alcohol and you'd hope they wake up the next morning with a clearer head," he said.

"Sine the last time we have upgraded our security and we are hoping police can identify these people."

The theft took place despite the recent addition of security cameras, fencing, and sensor lights at the museum and all dinosaur models in the garden are secured with chains.

Mr Mancuso said he had handed over the video footage of the incident to the police.

Any witnesses are encouraged to contact Crime Stoppers on 1800 333 000, or at act.crimestoppers.com.au.