Genetically Nervous and Normal Pointer Dogs: Relation Between Hearing and Behavioral Abnormalities

Abstract

Genetically nervous pointer dogs have been characterized in earlier works as an animal model for pathological anxiety.1–3 Individual differences in fearfulness were initially used to create two lines of pointer dogs.4,5 These lines have been maintained now for more than 20 years with continuous selection for the most fearful dogs in the nervous line and for the least fearful dogs in the normal line. Each line originated from a single male-female pair of each type. The behavioral traits of both fearfulness and normality have bred essentially true since the first generation.2 The nervous dogs begin to demonstrate from the age of 3–9 months a highly characteristic and reproducible pattern of fear-related behaviors to certain exogenous stimuli.6 In the absence of such stimuli, these dogs do not appear to be markedly different from the normal dogs: they move freely, play with other dogs, breed as well as the normal dogs, and adequately rear their pups or foster pups from the normal line.1 In contrast to these normal behaviors, exposure to humans, a sudden blast of a loud noise, and certain other stimuli elicit a dramatic expression of fear-related behaviors such as excessive timidity, hyperstartle, reduced exploratory activity, marked avoidance of the human observer, catatonic freezing cardiovascular changes, urination, and defecation.1,2 The normal dogs behave differently under those conditions as evidenced by friendly play with humans. They are active and inquisitive and comply without protest to experimental tasks,1,3 and despite such tasks they continue to approach man in a friendly fashion.1,3 The phenotypic expression of the nervous behavior in these dogs is not prevented by cross-rearing or by extra home-rearing, which produces only temporary changes compared to kennel rearing.7 Studies done in our group with these dogs included the evaluation of a hearing deficit and its relation to the abnormal behavior.