Animal Welfare Information Center Newsletter, Winter 1994/1995, Vol. 5 No. 4 *************************

The Wolf-Dog Hybrid

An Overview of a Controversial Animal

Robert A. Willems, DVM
Veterinary Medical Officer
USDA, Animal and Plant Health Inspection Service
Regulatory Enforcement and Animal Care
Western Sector, Sacramento, CA 95827

Photo:  Wolf-Dog HybridThe wolf has had an influence on the culture, art, and lore of human societies since before historical times. A traditional fear of wolves is deeply ingrained in many cultures, where they are often regarded as fearsome predators, not only of wildlife but also of humans and livestock. Such perceptions have resulted in wolves being hunted to extinction in many parts of the world where they once were plentiful.

In American culture, the image of the "big, bad wolf" has been pervasive. This view has been changing over the past few decades as reports from naturalists studying both wild and captive wolves have dispelled many of the myths and misconceptions surrounding these animals.

Changing perceptions have resulted in an increased interest in wolves and things related to them. Chief among these has been the growing popularity of the wolf-dog hybrid, more commonly referred to as the wolf hybrid.

A wolf hybrid is the offspring of a breeding between a wolf (Canis lupus) and a dog (Canis familiaris). Breeding is possible since wolves and dogs are closely related genetically.

Though estimates vary, the current population of hybrids in the United States has been reported to be around 300,000. Growing interest in them has led to a proliferation in the number of wolf hybrid breeders, with many profiting from the breed's increasing popularity.

In addition, a small but energetic industry has sprung up around the animal. A number of publications, periodicals, and at least two registries are devoted to the breed. Several regional and national wolf hybrid organizations catering to breeders, owners, and enthusiasts have also become established.

As their numbers continue to increase, wolf hybrids have become the center of a growing controversy. A number of attacks on people--mostly children--have resulted in severe injuries and several deaths. Consequently, many people have begun to question whether such animals belong in their communities, or whether they should exist at all.

Despite growing attention, wolf hybrids remain largely misunderstood. Their poorly defined nature and lack of a stable identity have helped fuel the controversy surrounding them.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References


When considering the wolf hybrid, one cannot avoid discussing both the wolf and the dog. It is commonly accepted that the modern dog resulted from the domestication of the wolf, a process that began 12,000 to 15,000 years ago. Until this century, there has been little further interest in cross-breeding the two species.

It is likely that wolves and dogs have sporadically interbred in nature for as long as both species have coexisted. Most matings probably occurred between roaming or feral dogs and wolves living apart from a pack.

The offspring from such matings may have posed a hazard to the human communities near where they lived. After studying numerous historical and modern accounts of wolf attacks on humans, the Canadian naturalist C.H.D. Clarke concluded that most attacks involved either rabid wolves or hybrids.

One such event may have occurred in the Cevennes region of south central France between the years 1764 and 1767, when about 100 people were attacked and at least 64 killed by what was described as a pair of savage wolves. Most of the victims were children. These animals came to be known in local lore as the "beasts of Gevaudan." After being hunted and killed, it was found that the male weighed about 140 pounds and the female about 110 pounds; these weights were unusually high for the local wolf population. Their marked aggressiveness and other described physical attributes have led to speculation that these two animals may have been wolf hybrids, perhaps siblings born from the breeding of a wolf with one of the large dog breeds commonly kept by farmers in the region.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References

Physical Characteristics

Wolf hybrids have been known to exhibit physical characteristics of both the wolf and dog in differing combinations and to varying degrees. Though closely related, there are a number of anatomical and physiological differences between the two species.

Wolves generally weigh between 80 and 100 pounds, with females weighing less than males. An unusual wolf may reach 150 pounds or more. They have slim torsos with narrow chests, long legs with large feet, and large heads with larger teeth and more powerful jaws than those of the dog. Their coat varies with the seasons; it is very thick with a dense undercoat in the winter and sheds to a thinner, shorter haired coat in the summer. Coat color varies from all black to a grizzled gray to all white. The eyes are usually a yellowish golden color.

Dogs come in a variety of sizes, shapes, and colors that vary greatly with the breed. The malamute and husky closely resemble the wolf in appearance, making them the dog breeds most preferred for hybridization.

Wolves are seasonal breeders and generally have two to four pups per litter. Dogs are nonseasonal breeders and generally have larger litters than wolves.

Because of the range of possible variations, there is no general description that can be made of the wolf hybrid. They are often larger in size than either the wolf or dog from which they were bred, a phenomenon termed "hybrid vigor." Though most high- percentage hybrids often retain much of the physical appearance of the wolf, many hybrids are indistinguishable from dogs in appearance.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References

Breeding and Genetics

Although most breeders raise hybrids to sell to the public, there is a small group of breeders and enthusiasts seeking to establish a new and distinct breed of canine. Their long-term goal, as described by one well-known breeder, is to obtain an "ideal... a wolf/dog cross strongly and attractively resembling its wolf counterpart visually, slightly aloof and territorial, but easily managed by its owner" (Dorothy Prendergast, The Wolf Hybrid, p.6). While most breeders would readily agree with this ideal, not all agree on the means to achieve it.

Theoretically, a wolf hybrid can result from the mating of a wolf with any breed of dog. Wolves have been bred with such diverse breeds as malamutes, Siberian huskies, German shepherds, rottweilers, collies, pit bulls, and even standard poodles.

The initial mating most commonly occurs between a male dog and a female wolf, though the opposite mating can also occur. The offspring produced from such a mating are first generation, or F1, hybrids. F1 and subsequent hybrids can then be bred with other hybrids, with pure wolves, or with the same or different breeds of dog, resulting in a group of hybrids with a wide range of genetic makeup.

This genetic makeup is most often represented as a percentage, a number which is presumed to be a measure of the amount of wolf blood in the animal. The percentage not only represents the lineage of a hybrid, but is often used to determine its selling price as well.

A 2-year-old, high percentage wolf-dog hybrid.
(Photo by R. WIllems)

When advertised for sale, hybrids are often described by a baffling array of percentages that purport to accurately represent the amount of wolf blood in the animal being sold. There is no uniformity amongst breeders in the way these percentage figures are determined, and a breeder can assign percentages to their animals by using several different methods. The most common, which may be termed the "pedigree method," is to add together the "known" percentages of wolf in the two parents and divide the sum by two to get the percentage of wolf in the offspring. Thus, when a pure (100 percent) wolf is bred to a pure (0 percent) dog, the offspring, an F1 hybrid, will be 50 percent wolf. If this F1 is then bred to another pure wolf, the result would be a 75 percent hybrid.

The pedigree method is considered by most breeders to be the only ethical way of calculating percentages, but it is not the only method used. A few breeders assign percentages to their hybrids based on the animal's physical appearance, others use systems known only to themselves, and some use any percentage that will fetch a decent selling price.

Although there is much discussion of percentages in wolf hybrid circles, few understand what these numbers actually mean. To most breeders and owners, they represent the exact "wolf content" of their animals. Unfortunately, the biological mechanisms and events that govern the inheritance of genetic material--and the resulting statistical complexities--cannot be accurately represented by the simple formula of the pedigree method. The inaccuracy of these percentages becomes apparent when one examines the genetics of hybridization.

Wolves and dogs each have 78 chromosomes arranged into 39 pairs. Wolves are physically different from dogs because they have a number of genes located on these chromosomes, coding for wolf characteristics, that dogs do not have. But which genes differentiate a wolf from a dog? How many are they and on which chromosomes are they located? Unfortunately, the answers to these questions are not currently known.

Using the pedigree method, each pup in a given litter would be assigned the same percentage of wolf blood. Yet no two pups in that litter have the identical genotype, unless they are identical twins. This is easily demonstrated by noting the differences in physical appearance, or phenotype, amongst the pups. Some will be more wolf-like than others. These phenotypic differences reflect the differences in their genotypes.

One complicating factor in determining accurate percentages results from the close biological relationship of wolves to dogs. As previously stated, wolves are recent ancestors of the domestic dog. Though not identical, the genotypes of wolves and dogs are very similar. It is probable, in fact, that 99 percent or more of the genotypes of these two species are indistinguishable. (Consider that 98 percent of the genotypes of humans and chimpanzees are indistinguishable.) The large majority of wolf genes that enter into pedigree percentage calculations are, therefore, identical to the corresponding dog genes.

There may be as few as several hundred genes in a genotype containing more than a 100,000 genes that differentiate the wolf from the dog. But the locations of these genes on the various chromosomes are unknown. They may be located on all or only a few of the 39 chromosome pairs, making it unlikely for them to be evenly distributed between daughter cells following the random separation of chromosomes that occurs during meiosis.

With current knowledge and technology, it is not possible to accurately determine the percentage of wolf genes in a wolf hybrid. Therefore, although they do not accurately represent the "wolf content" of an individual hybrid, the percentages assigned to wolf hybrids by the pedigree method may still have some value. Pedigrees are a traditional way of determining ancestry in human lineages as well as animal breeding. These percentages, if honestly assigned and accurately calculated, can be used to depict the breeding history and ancestry--the pedigree--of the individual animal. Since there is no way of accurately calculating the percentage of wolf genes in a hybrid, it may still be the best method currently in use to describe an individual hybrid.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References


Much of the controversy over wolf hybrids centers around their behavior. Unfortunately, there is little scientific literature on the subject. Most of what we now know about their behavior comes from anecdotal accounts found in news stories, magazine articles, and reports from individuals.

The absence of an objective behavioral study of this animal has contributed to the wolf hybrid controversy, and most opinions of their behavior can be readily divided between two opposing camps. One side describes them as being highly aggressive, destructive, unpredictable, and untrustworthy around humans, especially children. The other sees them as gentle, playful, intelligent, and loving animals, similar to the dog in their relations with people. In fact, many experienced hybrid owners claim that their animals are less dangerous than some breeds of dogs. Adding to the confusion, national statistics on canine attacks on humans compiled by the Centers for Disease Control and Prevention (CDCP) have been used by both sides to support their differing positions.

Even without a formal study, many aspects of hybrid behavior can be extrapolated from the known behaviors of dogs and wolves. Research has shown that many of the behavioral traits of these two animals are inherited, and their basic behavior patterns are fairly predictable.

Although anatomical differences between wolves and dogs are slight, the most notable difference between the two species is their behaviors. Animal behaviorist Michael W. Fox has described the domestic dog as a wolf with no behavioral patterns added, but with some patterns modified or reduced. As an example, the behavior of a wolf following a challenge or threat display is highly predictable. Similar displays by a dog, especially when directed toward a human, are much less predictive of the dog's ensuing behavior. This is a result of the modification of the social behavior patterns of dogs that occurred during domestication.

There are many other behavioral differences between wolves and dogs. Wolves in the wild appear to fear humans and will avoid contact whenever possible. (Wolves raised in captivity are not as fearful of humans. This suggests that such fear may be learned rather than inherited.) Dogs, on the other hand, socialize quite readily with humans, often preferring human company to that of other dogs. Wolves are tremendously successful hunters. Most dogs would quickly starve to death if left to fend for themselves in the wild. Additionally, wolves rarely bark, something obviously not true for most dogs. Since wolf hybrids are genetic mixtures of wolves and dogs, they can inherit a range of behavioral traits, some of which may be conflicting.

This mixture of potentially conflicting genetic traits results in less predictive behavior patterns in the wolf hybrid, compared to either the wolf or dog. This is not to say that the behavior of a specific hybrid is unpredictable or erratic. It would, however, be unlikely that someone unfamiliar with a particular hybrid, even someone with considerable experience, would be able to predict that animal's behavior with reasonable certainty. The adult behavior of hybrid pups also cannot be predicted with anything near the certainty of dog pups. Thus, though the behavior of an individual wolf hybrid may be predictable, the behavior of the breed as a whole is not.

Their aggressive tendencies and attacks on humans have caused many people to have concerns about wolf hybrids. Some question whether they are as dangerous as many claim. When CDCP statistics on canine attacks are used to compare hybrid attacks to those committed by various breeds of dogs, hybrids appear to be no more dangerous than some of the more aggressive dog breeds. But, these statistics may be misleading since they only list the number of attacks by breed without taking into account breed population figures or circumstances surrounding the attacks.

Some insight into hybrid aggressiveness can be attained by looking at aggression in wolves and dogs. Wolves are relatively non-aggressive animals. Fighting amongst pack members is detrimental to the pack's survival, and aggressive behavior has been selectively inhibited in the wolf during its evolution. However, aggression in wolves can be part of territorial or protective behavior, but is most commonly seen during social posturing within the pack. This type of aggression often appears to be unprovoked, and is an attempt to establish or maintain dominance over a subordinate animal. The majority of human bites by captive wolves have occurred during dominance challenges. Wolves in captivity, though, rarely kill humans.

Dogs are more aggressive than wolves, because they were not subject to the same selective pressures as the wolf. In addition, a number of dog breeds were developed specifically for their fighting ability and aggressive tendencies.

Aggressive behavior in the wolf hybrid is variable. The degree of aggressiveness appears to be related to the percentage of wolf and breed of dog in the hybrid. High-percentage hybrids tend to show the decreased aggressiveness of the wolf. There is an account of an auto junkyard owner who bought a high-percentage hybrid, thinking it would make a good guard dog. Rather than guarding the property, the animal instead would often hide behind the stacks of old cars whenever a person would enter the yard.

Some hybrids can be more aggressive than the dog. Aggressive hybrids usually come from breeding with aggressive dog breeds, such as pit bulls or rottweilers.

Though animal attacks on humans are often attributed to aggressiveness, some attacks can be related to predatory behavior. Aggression is often confused with predation, but the two are distinctly different. Both wolves and dogs exhibit predatory behavior, but the wolf is the far superior hunter.

There are differences in the predatory instincts of dogs and wolves. Wolves in the wild will occasionally prey on humans, though rarely and only under unusual circumstances. Predatory behavior of dogs toward humans has been greatly suppressed by domestication.

When considering predatory attacks on humans, an awareness of the relationship between a predator and its prey is critical. A prey animal often gives certain signals to the predator that stimulate its predatory impulses. Some of these signals, such as fleeing or signs of injury, are easy for us to recognize. There may be a number of additional signals that go unnoticed by human observers, which are recognizable to the predator. This concept is important in understanding attacks by predatory animals on humans.

Most attacks by wolf hybrids have been on small children. Many occurred when the animal's predatory instincts were triggered by some unwitting behavior by the child, causing the hybrid to regard the child as prey. In several instances, hybrids have even attacked children that they have played with repeatedly in the past.

In some hybrids, the timidity of the wolf may be replaced by the aggressiveness of the dog, while the predatory contribution from the wolf ancestry may remain relatively intact. Thus, hybrid attacks on humans can be related to both the aggressive tendencies of the dog and the predatory nature of the wolf.

Social behavior is also important to both the dog and wolf. The wolf has a complex social structure centered around establishment of the pack. Dominance behavior is an important part of establishing the social hierarchy of the pack, and the dominance of higher ranked animals is constantly being challenged by their subordinates. The social environment of the dog is centered around its association with humans, with all humans, in general, being dominant to the dog. Wolves do not socialize with humans in the same way as dogs do, however. Captive wolves usually regard humans simply as other wolves in the pack, and challenges to the "alpha" human are not uncommon.

In hybrids, where the aggressive nature of the dog may be coupled with an absence of the wolf's aggressive restraint, serious injury or even death to a human can result during a dominance challenge. Hybrids having strong natural dominance tendencies may be particularly dangerous.

There are other troubling aspects of wolf hybrid behavior. Hybrids are often unsuitable in the home environment. Many retain the natural tendency toward destruction that makes the wolf such a poor house pet. Wolves are very curious animals by nature, and may destroy such large items as sofas, tables, and cabinets while attempting to satisfy their curiosity. They are also notoriously difficult to housebreak. Outdoors, wolves are excellent diggers, and can burrow as much as 6 feet underground, destroying yards and defying many poorly conceived attempts to keep them confined. Many hybrids retain these wolf-like behaviors, making them particularly undesirable as pets.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References

Ownership of Wolf Hybrids

There is a mystique surrounding the ownership of a wolf hybrid. Those unfamiliar with it often wonder why anyone would want to own one of these animals. Most owners purchase their hybrids as companion animals. Many do so out of a desire to own an animal that is unusual and possesses a "feel of the wild."

Most people have very little knowledge of wolf hybrids before they purchase one. Disreputable sellers may provide the buyer with erroneous, little, or no information on care and housing for the animal. In fact, the true nature of the hybrid may be purposely misrepresented by the seller in order to assure a sale. As a result, many owners quickly become disillusioned when the cute pup they purchased matures and becomes unmanageable, destroying their home, digging out of the yard, and becoming a nuisance in the neighborhood or a menace to their children.

Of course, there are many owners who love their hybrids and enjoy ownership. These owners are usually those who have taken the time to learn about their animal and realize that a wolf hybrid can not be treated as just another dog. The satisfied owner is one who is willing to provide the housing necessary to properly maintain such an animal, and not to chain it up out in the yard when it is no longer suitable for living in the house. Most responsible owners house their animals in enclosures similar to those used to house wolves. Such housing generally increases the cost of ownership, and the less responsible owner commonly opts for substandard housing in an attempt to save money.

A female, high percentage wolf-dog hybrid
(Photo by R. WIllems)

Wolf hybrid breeders generally advertise their animals for sale through advertisements in newspapers, periodicals, and newsletters. They sell for prices ranging from $100 to as much as $1,500. Such prices are a major cause of the recent proliferation in the number of wolf hybrid breeders. Although most breeders are honest in the sale of their animals, there is a good deal of fraud in the wolf hybrid trade. It is not unusual for a large mixed breed dog with no wolf blood at all to be sold as a wolf hybrid for a large amount of money. Additionally, few wolf hybrid breeders own or have access to a pure wolf. After several generations without the infusion of new wolf blood, the genetic makeup of the hybrids from such a kennel would be extremely confused.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References

Animal Control and Legal Issues

Regulation of wolf hybrids varies greatly in different parts of the country. Federal Animal Welfare Act regulations define hybrids as domestic animals, and they are regulated as are other dogs. Several States require permits to keep hybrids, a few States prohibit their possession, and many States do not regulate them at all.

Hybrids can pose perplexing problems for local animal control agencies. The question of jurisdiction is often unclear. Local animal control ordinances are often written exclusively for dogs. Most State wildlife agencies do not regard wolf hybrids as wildlife even though the animals may be legally defined as being wild or exotic. As a result, many hybrids may not be regulated by any local statute, making troublesome animals and owners a difficult problem for their communities.

Yet another problem for animal control agencies is the difficulty in identifying an animal as a wolf hybrid. There is no test currently available that will differentiate a hybrid from a dog or a wolf. Animal control agencies often must rely solely on the word of the owner in determining whether or not an animal is a wolf hybrid. Recently developed techniques, such as genetic probing, hold some promise as possible methods of identification, but no work is currently being done with regard to wolf hybrids.

Many animal shelters have had difficulties dealing with hybrids. Aside from housing and handling concerns, adoption to the public has proven to be risky. In 1988, a wolf hybrid was adopted from a humane society shelter in Florida. Several hours after it was taken home, it escaped from its new owner's fenced yard and killed a neighbor's 4-year-old boy. The shelter was sued and paid $425,000 in a settlement to the child's parents. Since this incident, shelters around the country have been reluctant to put these animals up for adoption. Instead, the animals are euthanized once the required holding period is over.

Rabies vaccination for wolf hybrids is yet another difficult issue. Although it is likely that current rabies vaccines are as efficacious in the hybrid as they are in the dog, Federal regulations require that any vaccine be tested in a species before it can be approved for use in that species. Due to the expense, no such testing has ever been done on either wolves or hybrids. Regardless, many hybrids have been vaccinated with canine rabies vaccine. Such vaccinations are not officially recommended or recognized, and in some States may even be illegal. Consequently, hybrids that have bitten someone are often treated differently than a dog would be. In many cases the hybrid must be destroyed and the brain examined, regardless of whether or not it was vaccinated for rabies.

In some States, veterinarians have had legal problems as a result of treating wolf hybrids in their practices. Recently, a veterinarian in New Jersey was sued and found liable for damages after a wolf hybrid he had treated later bit someone. To further complicate matters, veterinarians may find that their malpractice insurance does not offer coverage in a suit involving a wolf hybrid, if the hybrid has no permit or is owned illegally. The American Veterinary Medical Association recently issued a statement saying that their malpractice insurance carrier would not cover suits involving wolf hybrids if the animal's owner has no permit in a State that requires one, or if hybrids are prohibited in the State in which the incident occurred.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References


The wolf hybrid is quickly growing in popularity in the United States. Those who own and breed wolf hybrids defend them as being a viable alternative to the dog for those who want a more exotic pet. Others regard them as potential "time bombs" ready to go off unexpectedly, injuring the owner or some unsuspecting person. The latter would like to see their breeding and sale prohibited. Many more are becoming concerned as the problems associated with these animals increase and more incidents occur.

Discussions of wolf hybrids often become heated emotional exchanges between opposing parties, each with their own sets of data, statistics, and information. Despite opposition and attempts at regulation, the wolf hybrid population continues to increase as a result of continued demand for the animal by a certain segment of the public. Whatever opinion one has, the presence of wolf hybrids has forced more and more communities to become embroiled in the controversy that continues to surround these animals.

To: Introduction | Background | Physical Characteristics | Breeding and Genetics | Behavior | Ownership of Wolf Hybrids | Animal Control and Legal Issues | Conclusion | References


This article appeared in the Animal Welfare Information Center Newsletter, Volume 5, Number 4, Winter 1994/1995

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