Over 600 animals were found in the home of a Los Angeles woman, arrested on suspicion of animal cruelty. Some of the animals were already dead and some so ill they had to be euthanized by Animal Services. The woman insisted the animals were well-cared for and her home was clean, despite physical evidence to the contrary. She refused to voluntarily surrender the animals to animal control. Her fear? They would be euthanized. This woman could be described as an animal hoarder.

According to Gini Barrett, director of the American Humane Association Western Regional Office (Tamaki, 1997), animal hoarders are well-known to animal care professionals. "Collectors exist in almost every community, large or small, rural or urban. They are in a state of denial that prevents them from seeing the filth or understanding their animals are sick, dying or dead. They need help," she said.

The Symptoms of Animal Hoarding
While animal care specialists recognize these people are in need of psychiatric help, almost no psychiatric literature exists on this topic. The existing literature on the hoarding of animals by human beings has been written by officials of the Humane Society of the United States and animal shelter operators (e.g., Lockwood and Cassidy, 1988). Only one case series appears in medical or psychological literature. Worth and Beck (1981) interviewed multiple pet owners identified from complaint files of the New York City department of health and animal control agency and from their own personal acquaintance. Most of those studied collected dogs, or cats; men more often collected dogs, and women more often collected cats. Nearly two-thirds of their sample were women, and 70% were unmarried. Social isolation was common but appeared to result from the hoarding behavior rather than causing it. Most participants reported their collecting started in childhood. Many had no telephone, public utilities or plumbing, and many hoarded inanimate objects as well.

The authors speculated that their participants adopted a parental role with respect to their animals. This resulted in reluctance to remove any animals, even when adequate homes were available. Many of the collectors emphasized that their animals gave them "unquestioning and uncritical love." They tended to personalize and anthropomorphize their pets and viewed themselves as rescuers of suffering or unloved animals (Worth and Beck, 1981).

More recently, Patronek (1999) surveyed animal shelter operators about their experiences with people who hoard animals. Detailed information was obtained on 54 cases. An animal hoarder was defined as "someone who accumulates a large number of animals; fails to provide minimal standards of nutrition, sanitation and veterinary care; and fails to act on the deteriorating condition of the animals (including disease, starvation and even death) or the environment (severely overcrowded and unsanitary conditions), or the negative impact of the collection on their own health and well-being." These findings support some of Worth and Beck's conclusions. Most cases were female (76%), a large proportion (46%) were 60 years of age or older; most were single, divorced or widowed; and almost half lived alone. The most common animals involved were cats (65%) and dogs (60%). Based on the data collected, Patronek estimated that there are 700 to 2,000 new cases of animal hoarding every year in the United States.

The conditions described were fairly consistent in both studies. Dead or sick animals were discovered in 80% of reported cases, yet in nearly 60% of cases the hoarder would not acknowledge the problem (Patronek, 1999). In 69% of cases, animal feces and urine accumulated in living areas, and over one-quarter of the hoarders' beds were soiled with feces or urine. Hoarders' justifications for their behavior included an intense love of animals, the feeling that animals were surrogate children, the belief that no one else would or could take care of them, and the fear that the animals would be euthanized. As in Worth and Beck's (1981) report, a significant number of hoarders had nonfunctional utilities (i.e., bathroom plumbing, cooking facilities, heat, refrigeration and electricity).

The resolution of these cases was often protracted and difficult, and the hoarder frequently resumed the behavior. Sixty percent of the hoarders studied were repeat offenders. Many of the caseworkers expressed frustration with the perceived lack of cooperation from public and mental health professionals (Patronek, 1999).

To date, information about animal hoarders has been provided secondhand by officers and caseworkers investigating these individuals. Only one study has collected information directly from the animal hoarders. To address this problem, the Hoarding of Animals Research Consortium (HARC) was formed in conjunction with the Tufts Center for Animals and Public Policy, Boston University, Northeastern University, Smith College and the Massachusetts Society for the Prevention of Cruelty to Animals. The first HARC project was to interview people who meet the definition of an animal hoarder as well as people who own multiple pets but do not show the lack of care of their animals that is characteristic of hoarders.

Of nine interviews conducted to date, seven subjects were true animal hoarders and two had multiple pets but no problems in caring for them. Reports from these individuals are consistent with much of the information in the Patronek (1999) and Worth and Beck (1981)studies. All nine interviewees were female and most were over 40 years old. Five lived alone, two lived with a husband, two with children and one lived with her mother. Most of those interviewed also hoarded objects, causing their homes to be cluttered and disorganized. Other characteristics included the beliefs that they had special abilities to communicate or empathize with animals, that animal control officials failed to recognize the care the interviewees give to their animals and that saving animals was their life's mission. Typically, animals played significant roles in their childhoods, which were often characterized by chaotic, inconsistent and unstable parenting.

Explanatory Models for Animal Hoarding
Several psychiatric models have been suggested for problematic animal hoarding (Lockwood, 1994). The delusional model suggests that people who hoard animals suffer from a highly focused form of delusional disorder. Two pieces of anecdotal information support this model. First, in our pilot study, participants all firmly believed they had a special ability to communicate and/or empathize with animals. Furthermore, the hoarders insisted that their animals were healthy and well-cared for. This claim, in the midst of clear and immediate information to the contrary, suggests a belief system out of touch with reality. One interesting finding is that, outside the context of their relationship to their animals, many of these people appear reasonably normal and healthy.

Patronek (1999) suggested that animal hoarding may be a "warning sign for early stages of dementia," which would suggest a dementia model. This was based on the number of people who were placed in a residential facility or under guardianship (26%) and that the individuals showed no insight into the irrationality of their behavior. Furthermore, hoarding of inanimate objects occurs in about 20% of dementia cases (Hwang et al., 1998). There is little direct evidence for this model, however. It was not established whether institutional placement was due to dementia, and lack of insight is common in disorders other than dementia (e.g., obsessive-compulsive disorder or anorexia). Further, the hoarding of possessions is accompanied by an inability to recognize the problem (Frost and Steketee, 1998), yet our work does not show it to be closely associated with cognitive dysfunction.

Lockwood (1994) suggested an addictions model based on similarities to substance abuse, including a preoccupation with animals, denial of a problem, excuses for the behavior, isolation from society, claims of persecution, and neglect of personal and environmental conditions. Other evidence consistent with this model comes from research on impulse control problems. In particular, the hoarding of possessions is associated with several impulse control problems including compulsive shopping (Frost et al., 1998) and gambling (Meagher et al., 1999). Some animal hoarders report compulsive collecting of strays or shelter animals.

Small numbers of animal hoarders may be explained by a zoophilia model, in which animals serve as sexual gratification (Lockwood, 1994). Although in a few cases reported by the popular media collected animals were the objects of sexual activity, there is little evidence to support this model as a major determinant of this behavior.
Another possible model for animal hoarding is an attachment model in which the individual suffers from early developmental deprivation of parental attachment and is unable to establish close human relationships in adulthood. This situation may result from childhood experiences of absent, neglectful or abusive parents or caretakers. The chaotic households and inconsistent parenting observed in the HARC interviews, as well as the desire for unconditional love from animals described in Worth and Beck's report (1981), provide some support for this model. This model is also consistent with current theorizing about the hoarding of possessions.

Perhaps the most parsimonious model ties animal hoarding to OCD (Lockwood, 1994). Two major features are consistent with the OCD model. People with this syndrome appear to experience an overwhelming sense of responsibility for preventing imagined harm to animals, and they engage in unrealistic steps to fulfill this responsibility. OCD patients experience this same sense of excessive responsibility for preventing harm and engage in unrealistic ritualization to prevent it.

In addition, Patronek (1999) indicated that over 80% of animal hoarders also hoarded inanimate objects. Similar data come from Worth and Beck (1981) and from our HARC pilot study. Hoarding of possessions occurs in 20% to 30% of OCD patients (Frost et al., 1996), although it is a symptom that is somewhat distinct from other symptoms of OCD (Summerfeldt et al., 1999). The substantial overlap of possession hoarding and animal hoarding suggests that an OCD model may be useful. Hoarding of inanimate objects has received some attention in the scientific literature recently and may guide development of a conceptual model of animal hoarding.

Models for Hoarding of Objects and Animals
Frost and Gross (1993) define hoarding as "the acquisition of, and failure to discard, possessions that appear to be useless or of limited value." For this behavior to pose a clinically significant problem, Frost and Hartl (1996) suggested that living spaces have to be "sufficiently cluttered so as to preclude activities for which those spaces were designed," and the hoarding must create significant distress or impairment.

Hoarding of possessions involves three classes of problematic behaviors: acquisition, saving and disorganization. In most, if not all, cases of compulsive hoarding, compulsive acquisition (buying or collecting free things) plays a major part (Frost et al., 1998; Winsberg et al., 1999). People who hoard possessions score significantly higher on measures of compulsive buying and compulsive acquisition of free things (Frost et al., 1998). Recent data from our laboratory suggest that people who identify themselves as having problems with compulsive buying also tend to have problems with hoarding behavior (Frost et al., 1999). Central to this phenomenon is the inability to resist the urge to acquire an object, even though acquiring or possessing the object may create problems (e.g., financial, clutter and so on). People who hoard animals experience similar urges when seeing or hearing about an animal in need of a home.

The classic picture of the compulsive hoarder is the individual who saves everything and can throw nothing away. According to Frost and Gross (1993) possessions may be saved by both hoarders and non-hoarders for several different reasons. These include their sentimental value (emotional reasons or reminders of important life events), instrumental value (potential usefulness) or intrinsic value (beauty or attractiveness). The difference between people who hoard possessions and those who do not is that hoarders judge more possessions to have these values. This may also be true for people who hoard animals. Their attachment to animals is, in all likelihood, similar to other people's attachment, but it is applied to a much larger number or wider array of animals.

People who hoard possessions also have significant problems with organizing and maintaining their possessions (Frost and Steketee, 1998; Frost et al., 1995). This may be the most problematic feature of hoarding and the one responsible for the excessive clutter and chaos in the homes of people with this problem. Our experience suggests that this manifestation of hoarding must be addressed in any attempt to treat this problem. Anecdotal information about people who hoard animals suggests that their homes are typically in disrepair and apparent chaos. Similar problems with organization may prove evident among this group.

A recently developed cognitive-behavioral model describes compulsive hoarding as a multifaceted problem that stems from several deficits or difficulties (Frost and Hartl, 1996). These include information-processing problems, problems with emotional attachments to possessions and distorted beliefs about possessions. Avoidance of each of these problems leads to the chaos and clutter.

Information-processing deficits include problems with decision making that may result, in part, from difficulties in attending to, organizing and weighing relevant information. In particular, people who hoard seem to have difficulty with the process of categorization, which is necessary for organizing possessions. While there is no direct evidence that this applies to people who hoard animals, Patronek's study (1999) suggests animal hoarders have considerable difficulty maintaining a fully functioning home. This may reflect an inability to organize information, time and resources to complete basic tasks.

People who hoard possessions frequently identify their possessions as central to their identity so that losing (i.e., discarding) a possession often produces a grief-like reaction and sense of loss of part of themselves. Preliminary data from the HARC study suggest a similar phenomenon with respect to animals, even when the animals are not longtime pets. It may be that the mere sight of an animal in need of a home prompts an emotional attachment so powerful that the animal must be acquired. Once acquired, the animal receives very little attention to its basic needs yet cannot be given away.

Pilot interviews by HARC are consistent with the attachment model in finding that childhood experiences of abuse, neglect or extreme instability in the family may play a role in the development of hoarding. In several cases, animals served as stable fixtures in otherwise chaotic homes. Perhaps, in this context, animals serve an emotionally comforting role for vulnerable individuals, and attachments normally reserved for people are transferred to emotionally safer animals.

The finding that most people with this problem tend to be older and female (Patronek, 1999) suggests a developmental and gender-role link that may also have to do with feelings of vulnerability. Most of the people interviewed as part of the HARC project were relatively isolated and socially anxious, perhaps causing interactions with animals to be more comfortable than interactions with people. In these cases, animals may come to replace people in the hoarder's social world, which is consistent with the tendency observed among those interviewed to maintain their living spaces more like animal pens than human homes. This may suggest a disturbance in the way human attachments are formed.

Beliefs about the nature and function of possessions are another function of this model (Frost and Hartl, 1996), with a central belief being the hoarder's responsibility not to waste or misuse the possession. We suspect that a similar belief is prominent among people who hoard animals. Specifically, our preliminary findings suggest that people who hoard animals often believe they have a special gift for communicating or empathizing with animals, and that this is their life's mission (i.e., responsibility).

Some hoarders also express the need to maintain control over possessions. This results in increasing isolation and suspiciousness of others. We hypothesize a similar need for control among animal hoarders.

Like people who hoard possessions, animal hoarders often lack insight into the problematic nature of their behavior. A common and peculiar characteristic of people who hoard animals is a persistent and powerful belief that they are providing proper care for their animals, despite clear evidence to the contrary. In some cases, the home environment is so seriously impaired that the house must be torn down (Patronek, 1999). Careful assessment is needed to determine if this reflects a delusional disorder or overvalued ideation in the context of OCD. Delusional levels of paranoia regarding the actions and intentions of animal control officers frequently accompany this irrational belief.

Hoarders often cope with their behavioral deficits by avoiding them as much as possible. By saving things, the uncomfortable process of decision making is avoided, as well as the distress that accompanies discarding a cherished possession (Frost and Gross, 1993). Beliefs about responsibility and control and feelings of loss are never challenged by discarding and thus become rigidified. Likewise, animal hoarders may avoid uncomfortable decisions about turning away strays or treating sick animals by ignoring the problem or convincing themselves the animal is well. Similarly, dead animals are sometimes left to lie, perhaps to avoid feeling upset, guilty or responsible for the death. Thus, avoidance of discomfort may play an important role in the delusional features and possibly in other symptoms of pathological animal collecting.

Treatments for Animal Hoarding
To date, no research has addressed strategies for resolving cases of animal hoarding. What is clear is that adjudication of cases rarely alters the behavior. Until models for this behavior are established and tested, our understanding of this problem will be limited. Like many psychological conditions, the causes of animal hoarding are probably multiple and, therefore, assessment of emotions, behavior and thoughts must be multifaceted to point the way toward successful treatment.

For example, individuals with delusional thinking about their animals may benefit from relevant medications. Those with extreme attachment to their animals are likely to require long-term treatments and probably alternative sources of emotional connectedness. It is unclear whether those who hold strong beliefs about euthanasia and their perceived mission to save animals will be dissuaded from their convictions. Alternatives may be to forcibly limit their access to animals to prevent future problems, while addressing other features that lead to inadequate care of existing animals.

Research on animal hoarding is in its infancy, despite its seriousness and the frequency with which it is described in the news media. Directions for work on this problem include creating comprehensive methods of assessing the features and potential causes of animal hoarding and identifying potentially effective interventions to address the problem.

Acknowledgement
The Hoarding of Animals Research Consortium is a collaborative effort to study the hoarding of animals. Members of the consortium include: Arnie Arluke, Ph.D., Northeastern University; Carter Luke, Massachusetts Society for the Prevention of Cruelty to Animals; Edward Messner, M.D., Massachusetts General Hospital; Gary Patronek, V.M.D., Ph.D., Tufts University School of Veterinary Medicine; and Gail Steketee, Ph.D., Boston University.

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