Introduction

Very little is known about the effects of different aversive environments on animals. In dogs, 3 potentially traumatic situations are very common and involve hundreds of thousands of dogs: hoarding, large-scale breeding facilities (puppy mills), and abuse. Because these dogs are often adopted into households and presented to veterinarians for care, a better understanding of the physical and mental health exhibited by these dogs is essential.

Objectives

Three separate studies were undertaken to characterize the behavioral and psychological changes in dogs with these specific histories of adversity: confinement in hoarding situations, confinement in puppy mills, and abuse.

Methods

The caregivers of formerly hoarded dogs, former breeding dogs from puppy mills, and abused dogs were solicited for each separate study. Data collection was by online questionnaires completed by the dogs' caregivers. Data from the subject dogs were compared to findings from a large sample of typical pet dogs.

Results

The different groups of dogs all showed substantial differences as compared with the typical pet dog population and with each other. For example, puppy mill-breeding dogs displayed significantly higher rates of fear and significantly lower rates of aggression toward strangers and other dogs. In contrast, abused dogs showed significantly higher rates of aggression and fear toward unfamiliar humans and dogs.

Conclusions

Dogs having experienced specific aversive environments and events demonstrate a wide array of abnormal behavioral and psychological characteristics, which can endure for years and in some cases a lifetime.