Officers are appealing for information after a badger sett was attacked in the Scammonden Dam area.
Police say the poachers have tried to remove heavy stone and rubble in a bid to dig up the sett.
It is unclear whether any animals were taken.
The incident is being investigated by Calderdale’s wildlife officer, Special Constable Phil Sanderson.
He was contacted last Wednesday by the Calderdale Badger Monitor Group and is appealing to anyone who was in the area at the time and who may have seen anyone acting suspiciously, particularly if they were seen with dogs and spades, to get in touch.
“The area has an active badger monitor group who monitor all the setts in Calderdale on a regular basis and report all matters of interference or concern to the police,” he said.
“Badgers are a protected species by law, as is their habitation and anyone found interfering with a badger sett could face prosecution.
“Poachers can be charged with many offences, including criminal damage and theft, and will face arrest and conviction and the seizure of any vehicles, equipment and dogs used in the crimes.
“Poachers can also face disqualification from driving if they are using their vehicles for crime.”
Special Constable Sanderson said there have also been three attacks on badger setts in Barkisland this year, mainly in the Black Brook Valley area.
Anyone who witnessed anyone acting suspiciously in the area, or anyone who has any information about the incident, is urged to contact Special Constable Phil Sanderson or PC Fiona Igo at Todmorden Police Station on 101, or Crimestoppers, anonymously, on 0800 555111.