Organised gambling on which dog can kill a hare first is increasing in Northamptonshire, police say.
'Hare coursing' tends to happen in rural areas after the harvest is complete for the year.
It has been illegal for more than a decade but that does not deter everyone, with more and more reports in recent weeks.
PCSO Donna Fenner said: "Northamptonshire Police are receiving increased calls from around the county regarding this."
Usually, hare coursing it's carried out in groups.
Dogs flush out the hares in the fields and are then released from their leads to chase, and often kill, the hare.
The victor is determined by the first dog to catch and ‘turn' the hare or kill it.
PCSO Fenner said: "Frequently the practice is highly organised. Significant sums of money can change hands in the form of illegal betting and gambling on the outcome."
A report by World Animal Protection said gangs can rake in up to £10,000 per month by undertaking illegal activities such as hare coursing and poaching of deer and fish.
Hare coursing itself can attract a fine of up to £5,000, with the The Hunting Act also giving police officers the power to seize and crush vehicles used in committing the crime so they cannot be used again for similar purposes.
Northamptonshire Police said anyone witnessing illegal hare coursing in progress should call them immediately.
People with information about illegal hare coursing can contact Northamptonshire Police on the non-emergency number 101. Alternatively, they can call Crimestoppers anonymously on 0800 555 111