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: A dog with no history of biting that suddenly snaps when touched may be suffering from underlying conditions like hip dysplasia or osteoarthritis. House Soiling

(the study of animal behavior in natural environments) with clinical veterinary practice to diagnose and treat behavioral issues in domestic and captive wild animals. MSD Veterinary Manual 1. Scope and Core Disciplines Zooskool.com LINK

Essentially "doggy dementia" in senior pets. : A dog with no history of biting