Fast open-and-close

The dog quickly and repeatedly opens and closes its mouth approximately 1 cm wide; no threatening behaviours are exhibited and there is no forward movement.
(Murphy, 1998; van den Berg, 2003; Shilder, 2004)

VIDEO

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This video was filmed during a behavioural evaluation. This Tibetan mastiff is 4 years old. He is on a leash held by his owner and is also tied to a second lead. The dog has exhibited serious attacks against people in the past. An unfamiliar woman evaluator approaches the dog. The dog stares at the evaluator, who has stopped at a distance of 5 meters from the dog. The dog repeatedly exhibits fast opening and closing of the mouth.

facial fear display<>fighting against a muzzle