A West Australian priest has been fined $1000 for biting off the ear of a fellow elderly clergyman in a dispute over a sprinkler.

Thomas Henry Byrne, 81, was spared a criminal conviction after pleading guilty to assault occasioning bodily harm on Tuesday, because a Perth magistrate accepted dementia had played a central role in the attack.

A confrontation was sparked between the two men after the victim moved some objects around the shared yard of their Dianella complex on November 9.

As a result the victim's ear was completely severed.

It is understood the ear has been successfully reattached.