Police are receiving up to five reports a week of illegal hare coursing – the banned practice of setting dogs on the wild animals.
Officers have urged people in rural Leicestershire and Rutland to report all sightings of people carrying out the illegal 'blood sport' but not to approach the groups themselves.
The problem tends to increase at this time of year once crops have been harvested from fields, giving hare coursers and their dogs greater opportunities to spot their prey.
In many cases, a bet is made on which dog will catch the hare first. However, Leicestershire Police's wildlife officer, Special constable Paul Howland said he had no evidence this was the case in Leicestershire and Rutland.
Mr Howland said: "Roughly speaking we get between two and five reports of hare coursing per week in the whole of Leicestershire.
"These reports vary from seeing people walking lurcher, whippet or greyhound-type dogs in fields to hares being chased by dogs.
"The dogs cant chase through the crops so it happens mainly after harvest and early in the year.
"The main problems are that people trespass, sometimes damage crops that are still there and drive vehicles on to private land. Mainly though they are parked at the side of the road.
"Obviously the welfare of the animal comes in to question as they are often killed by the dogs when caught.
"We haven't had any reports of money changing hands and betting. It has been known to happen elsewhere, but not here.
"We would ask people to report any incidents they see to the police, the usual of a description of people or a number plate would be great news.
"But never to put yourself in harm's way and challenge anyone."
The Hunting Act 2004 made the practice illegal and anyone convicted of the offence can be fined up to £5,000 by a magistrates' court.
Police said the offenders would go to great lengths to cover their tracks.
One recent case reported to Leicestershire police by a landowner involved a group of suspects who were travelling in a vehicle which was fitted with stolen registration plates.
Hare coursing tends to start after harvest, usually around the end of August or start of September.
Police said coursing was more likely to take place at dawn or dusk but it can also take place in broad daylight.
A Melton area farmer, who asked not to be named, said: "They are not people to be crossed.
"They tend to come in vehicles and release the dogs across the land.
"As well as the harm to the animal, they can also damage newly sown crops when they drive their vehicles across the land.
"If people see them and get registration numbers that would help the police deal with these people."
Carol Puddephatt, of the Leicestershire branch of the National Farmers' Union, (NFU), said: "It is an illegal practice which harms the land and the hares and where possible people should report it to the police."
Contact Leicestershire Police on 101 or Crimestoppers, which is anonymous, on 0800 555 111.
