The protected creature was lured to a 'stink pit' at High Denton Farm, near Ilkley.
Austin Hawke, 51, of Ling Park, Ilkley, denied failing to inspect a snare every day it remained in position during a trial at Skipton Magistrates' Court.
Magistrates heard that Hawke, as head keeper of the Denton Park Estate, had set eight wire snares at four entrances to a 25 metre by 25 metre fenced off area of moorland.
The aim was to lure foxes, the target species which Hawke had a licence from Defra to destroy, to the pit.
The square pit had four entrance holes cut into the fencing mesh with the snares placed nearby.
The pit was around 100 metres away from a footpath.
Hawke claimed the snares had been 'deactivated' on Good Friday (March 30, 2018) because he was conscious there could be an increase in visitors and walkers to the moorland over the Easter break.
He admitted the snares had been left in situ but said the loops had been loosened and made so small as to prevent hares or badgers getting tangled in them.
He said the idea was to re-set them after a few weeks.
The badger had been found by walker and bird watcher Andrew Jowett on May 28.
The police were called to the site. Sergeant Stuart Grainger, of North Yorkshire Police, said he attended the site, one kilometre north of High Denton Farm, on May 29. The dead badger was in one of the snares which was attached to a wooden stake in the ground and "looked as if it had been dead for several days". He said it was in such an advanced state of decay that its innards fell away when it was raised from the ground. He said the snare had cut into the badger's flesh.
Defending, Amber Walker said her client had an exemplary record as a game keeper and was skilled in his job and honest.
"The snares were not left in such a state they posed a threat to non-target species. Mr Hawke has said if he had not been sure of this he would have gone back to check," she said.
She also claimed there was a possibility that animal rights activists could have been responsible in order to have the blame laid at the feet of the game keeper.
"Removing a head keeper (through conviction) would be quite a scalp (by some activists) even if it meant the death of a badger," she said.
Mr Yates claimed it was unlikely that animal rights people who campaigned against animal cruelty and disapproved of capturing animals would set snares.
Instead, he said Hawke had left the snares in position and was under a legal obligation to check them every 24 hours.
Magistrates found Hawke guilty of the charge, but stated it was an 'isolated act of negligence, rather than intent'.
The bench said it took into account his previous good character and gave him a conditional discharge for 12 months.
He was ordered to pay court costs of £625 and a surcharge of £20.
Sergeant Kev Kelly, of North Yorkshire Police’s Rural Task Force, said: “This case was reported following a member of the public who was aware of our proactive work under Operation Owl.
“From the evidence collected, it was apparent that the badger had suffered before it had eventually died after being caught in the snare. Therefore this case was fully investigated to ensure other animals didn’t undergo the same fate.
“If the defendant had been using breakaway snares it is less likely that he would have killed the badger.
“I am disappointed as we have been doing some really good partnership working with local Nidderdale keepers who want to show the public good practice and accountability.
“Hawke’s conviction will no doubt have an impact on how his profession is viewed. I think he has done his wider colleagues a disservice.”
Geoff Edmond, RSPCA National Wildlife Coordinator, said: “The RSPCA continues to work closely with the North Yorkshire Police’s Rural Task Force and this result highlights the strength of partnership working under Operation Owl.
“This badger will have suffered a horrific and prolonged death having been snared in this way.
Type of snare
Ilkley, Denton Moor