This handsome beast is a Sexton beetle. Also known as a "burying beetle" it senses a corpse (e.g. of a small rodent or bird) from a mile or more away with those combs on the end of the antennae, then digs beneath that corpse to bury it. Usually as part of a pair of beetles, it then tenderly raises its young using the corpse as a food source.

You can just see a small round, brown mite on this beetle's right eye, though it's a bit blurry. These are quite common and are thought not to parasitise the beetle directly, but to simply use it as transport between corpses. They may have a symbiotic relationship with the beetle, aiding in the management of the corpse by proving anti-fungicidal chemicals, but my brief research has thrown up a couple of slightly conflicting accounts.