Hypothesising:
Perhaps moggy was found in the hours of darkness on a road adjacent to farmland with a dog of the lurcher/greyhound type, probably on a slip lead, carrying a 1,000 candle power lamp attached to a belt mounted 12v battery. Perhaps lights had been seen playing over the field which might be expected to hold rabbits or hares.
If he was not actually seen to be committing any actual offence by the officers they would be right to report him for summons and seize any relevant evidence.
After their report and any other corroborating evidence from third party witnesses had been considered a summons would be issued for any relevant offences disclosed.
This could include poaching or going equipped to poach.
He would only be taken to the Police station had he committed an arrestable offence or failed to co-operate with the Police ie refuse to give details which would ennable a summons to be served.