Feeding activity and rumination of grazing sheep was studied by a vibracorder modified for recording the lower jaw movements. This light apparatus was placed in a canvas bag on the back of the animals and held in place with a harness. The jaw movements were transmitted via an air circuit composed of a rubber bulb maintained on the jaw with a halter, and connected by a tube to a cylinder piston system in the vibracorder. All these circuit components are in plastic, nylon and latex and thus highly watertight and shock resistant. The recorder paper was changed every day and the feeding activity and rumination easily discerned.