Insights Into the Behavior of Dogs Rescued from Animal Hoarders

Helping Dogs from Hoarders
By Jessica Hekman DVM, MS, October 2016, Updated June 2021

Like prisoners of war, dogs rescued from hoarding environments often carry the effects of their trauma with them for years. Until recently, we have lacked knowledge about how best to help these dogs recover, or even to understand how trauma affects their behavior. A new study provides some of the first data available about these dogs’ unique needs, and in doing so, suggests how to address them.

Frank McMillan, DVM, director of Well-Being Studies at Best Friends Animal Society in Utah, is committed to helping traumatized dogs recover from their experiences, including dogs rescued from animal hoarders. To assist in this quest, he recruited James Serpell, PhD, director of the Center for the Interaction of Animals and Society at the University of Pennsylvania School of Veterinary Medicine. Together, they are trying to learn more about the effects of trauma on dogs.

McMillan had questions: What’s different in the behavior of dogs who have been abused? What about dogs who lived as breeding animals in puppy mills, or in a hoarding environment? Serpell provided the means for finding answers: a validated questionnaire that the two researchers use to measure dogs’ behavior, and a massive database populated with information gleaned from 16,000 questionnaires filled out by dog owners from all over the world. This database allowed the researchers to compare the behaviors of the average dog to the behaviors of dogs from hoarding environments.

Best Friends Animal Society contacted owners and foster owners of previously hoarded dogs and asked them to fill out questionnaires about their dogs’ behavior. A comparison of their answers to the answers of the “average” dog owner in Serpell’s database provided the first scientific insights into how these dogs behave.


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Assembling the Data

Measuring a dog’s personality is a difficult task: Will behavior on the day we measure it have any relationship to behavior on another day? In other words, is a dog’s behavior at any given point in time actually a window into his personality? Serpell’s questionnaire, the Canine Behavioral Assessment & Research Questionnaire (C-BARQ), addresses this by asking the dog’s owner— the person who knows the dog best—to supply the information. The 100-item survey includes questions about the dog’s responses to specific situations, such as meeting unfamiliar dogs or visiting the veterinarian. Serpell’s team grouped the questions into related categories so that conclusions could be drawn about a dog’s general personality (for example, excitability and train-ability) and behavior issues (for example, stranger-directed aggression and dog-directed aggression).

In order for McMillan to be able to help potential adopters of hoarded dogs know what to expect, he needed to make comparisons. This proved to be somewhat trickier: Determining the ways in which these dogs’ behavior differed from the behavior of normal dogs first required a definition of “normal.” What is a normal dog? How likely is it that any dog will have aggression problems toward other dogs, and how much more likely is it that a dog from a hoarding situation will display aggression? To find out, Serpell queried the C-BARQ database, which—when compared to AVMA surveys—appears to provide a good representation of the variety of dogs living in homes in the U.S.

Some of the results of the comparison between the two groups of dogs were what the two researchers expected. Dogs from hoarding environments were dramatically more likely to be fearful of people, of other dogs or just of the world in general. (A terror of new things—and to them, everything is new—is one of the hallmarks of a dog from a hoarding situation.) Additionally, hoarded dogs have no opportunity to learn good house manners, and are more likely to eliminate in the house when left alone than the comparison dogs. Many of these dogs also dislike being touched or restrained, but simultaneously show a deep neediness and desire to be near people.

These results paint a picture of a dog who is not equipped at a basic level to interact normally with the world, and who is desperate to relate to humans but is not quite sure how to go about it. Serpell wonders if these attachment disorders are due to the disruption of the normal environment early in the dogs’ lives, followed by an environment with little to no individual attention. “You take them out of that situation,” he says, “and it looks like they hyperattach to the new owner.”

The study also turned up an increased incidence of compulsive behaviors in dogs rescued from hoarding environments: spinning, pacing, or licking blankets or carpets or even themselves. These repetitive behaviors, known as stereotypies, also appear in animals kept captive in other restricted, barren environments such as shelters and zoos with sub-standard facilities.

Stereotypies are thought to help animals deal with stress, and may remain even after the animal is in a less stressful environment.

Some of the results surprised the researchers, however. Although they suspected that many dogs in hoarding situations have had traumatic experiences with other dogs, the dogs in the hoarded group were less likely to display aggression to strange dogs, or to dogs in their household, than were the comparison dogs. As Serpell speculated, “You could imagine that in a hoarding household, where there are literally hundreds of dogs, any dog that engaged in dog rivalry is going to have a difficult time, so it kind of gets trained out of them. So they don’t show this type of behavior to the same extent as dogs living in, say, a two-dog household.”

He was also quite interested in a finding that dogs from hoarding situations are less likely to engage in persistent barking than dogs in the comparison group, unless they are rehomed with other dogs. “Barking, we know, is something that’s socially facilitated. So when one dog barks, it tends to trigger other dogs barking. It may be that these dogs are subjected to such incessant barking because of the numbers of dogs [in the hoarding environment] that they may habituate to it, and they no longer respond. Interestingly, when you take them out of that situation, that habit of barking doesn’t come back unless they’re in a household with another dog, which … triggers the behavior again,” Serpell suggests.

Many of the behaviors—or lack of them—described in these dogs suggest an animal paralyzed by fear; one who has developed learned helplessness and is reluctant to interact with the environment. In addition to decreased aggression, the owners of these dogs report decreased trainability, presumably because the dogs avoid interaction. One respondent reported that if something like a baby gate fell on her foster dog, “He would not even move out from under it, but would lie there passively.”

Because dogs are individuals, both Serpell and McMillan caution against over-interpretation of their results. The trauma of living in a hoard isn’t the same for any two dogs. “As part of a slide show, I present one case example of six dogs who came from the exact same facility, who show a huge variation in everything from fear levels to bonding with people,” McMillan says. The trends in the study are clear, but they are only trends; while they suggest that dogs with this background may be more likely to display specific behaviors, there’s no guarantee that every dog from a hoarding situation will display them. While they’re in the minority, some dogs come out of a hoard with their natural doggy friendliness and sociability intact.

Both McMillan and Serpell lamented the lack of complete histories for these dogs. Many are born into hoarding situations, and may grow up without being socialized to humans. If the hoarder was a woman, they may have never seen a male human before their rescue. Others are brought into the hoard as adults, perhaps as part of a dog sanctuary gone tragically wrong. These dogs may have received normal socialization and even training, and may be more able to adapt to life outside the hoard than a dog who has never known any other life. Whatever the circumstance, all information on origins is typically lost once a dog enters a hoard, and the C-BARQ has no way of determining if a particular dog’s resilience is due to an early life in a healthier environment, some minimal amount of socialization within the hoarding environment, genetics, or simply chance.

Participating in Dog Behavior Studies

You can fill out the C-BARQ for your dog at The scores on the test are relative, so you will receive a chart comparing your dog’s behavior to others of the same breed. There is no “perfect” score, and no failing mark. Serpell is currently seeking owners of American Staffordshire Terriers, English Bull Terriers and Alaskan Malamutes for a project on dogs with tail chasing and other compulsive behaviors. To find out about dog studies with other research groups, sign up at

Canine PTSD?

McMillan remarked on the way the individuality of each dog’s response mirrored the varied responses of humans to trauma. When asked if he felt that these dogs suffered from posttraumatic stress disorder (PTSD), he said that some of the aspects fit the criteria used to diagnose PTSD in people, “but not exact enough to where we can call it that … Part of the PTSD diagnosis involves … things going on cognitively that we can’t delve into [with dogs], such as intrusive memories, flashbacks, nightmares, that kind of a thing. So I hesitate to give that label to any of this.” He added that adopters of hoarded dogs frequently report that the dogs have what appear to be nightmares; in a follow-up to the original survey, he asked these adopters what human diagnosis they felt best fit their dogs, and more than half of them listed PTSD.

In that follow-up survey, McMillan also asked adopters about their experiences with these dogs, and received responses from 296 participants. This survey had no comparison group of “normal” dogs, and the adopters who chose to answer may have had more positive experiences with their particular dogs. Nevertheless, their responses were enlightening.

They describe dogs who lack trust in the world, who may be so fearful of being in a cage that they nearly stop breathing when kenneled at a veterinarian’s, who enter long fugues of licking the ground or a carpet. But the same dogs are also described as providing deep delight to their owners, who cherish every tiny step forward. These dogs can bond very closely; the terrified dog visitors see is not the same as the loving dog the owner sees. Most importantly, the respondents spoke about dramatic improvements. Many of these dogs will never be functionally normal, but over years of living in a healthy environment, their behavior has changed dramatically.

While more than two-thirds of respondents said they felt their dogs still had improvements to make in their behavior, they reported that they had already seen great advances in the dogs’ level of happiness and quality of life. As one wrote, “She is truly a happy, happy little soul when she is inside of her comfort zone.” Tellingly, 93 percent wrote that they would be willing to adopt this same dog again, even knowing what they now know about her behavior.

McMillan cautions against pushing these dogs too hard .For any fearful animal, but particularly for animals from hoarding cases, punishment may result in a setback. Adopters report that even strong words may be too much. The treatment that helped most was patience. Adopter after adopter wrote about learning to let the dog take each new step at his or her own pace. Pushing them before they were ready could result in increased fear. But giving the dog time to slowly learn that the world isn’t so scary reaped enormous benefits.

Other strategies included avoiding eye contact, which helped them gain confidence. For dogs who were afraid of hands, reinforcement with treats (tossed, not handed to the dog), rather than petting, was helpful. Some dogs benefited hugely from living with another, well-socialized dog who could show them the ropes and demonstrate how to be affectionate with humans. As some dogs came out of their shells, they responded well to positive reinforcement training in classes like agility, obedience and nosework.

Support Needed

Regrettably, those who adopted dogs from hoarding situations reported having difficulty finding support in the very difficult task of helping their dogs adjust. One adopter wrote, “There is little to no help available dealing with dogs with such social developmental deprivation. Dealing with physically abused dogs who have a basis of human trust in the beginning is very different than dealing with a neglected-from-birth hoarder dog. Behaviorists I’ve spoken to had no real concept of the differences.” (Though many trainers refer to themselves as behaviorists, for a dog with severe behavior problems such as the ones exhibited by many of these hoarded dogs, owners would do well to seek out professionals with advanced behavior training. Because many hoarded dogs display deep-seated fear for which medication can be helpful, a veterinary behaviorist who can prescribe medication may also be particularly helpful.)

McMillan is doing his best to provide information about what to expect from hoarded dogs and how to treat them. Among other things, he’s working on what he calls the “Manual for Care of Hoarded Dogs,” a 71-page document that will be posted on the Best Friends site when complete, included will be insights and quotes from the follow- up survey, as well as statistics, and McMillan’s own interpretations of what he found.

McMillan and Serpell believe that their study is the first to describe the behavior of dogs—or, in fact, any species— rescued from a hoarding environment. Ideally, more studies will follow, as we still don’t know enough about these dogs and how to help them. The hoarding environment is a difficult one to study, as alien to a healthy household as Antarctica is to Florida. Those who adopt these dogs need to be able to make informed choices about treatment strategies. Trying to adjust to the new and strange world of being a human’s companion must seem an almost insurmountable task to a once-hoarded dog. These dogs, and those who take them, in deserve our help.

Article first appeared in The Bark, Issue 87: Fall 2016

Photograph by Issarawat Tattong

Jessica Hekman, DVM, MS, completed a specialty internship in shelter medicine and now studies the genomics of dog behavior at the University of Illinois, Urbana.