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Compendium March 2008 (Vol 30, No 3)

Understanding Behavior: The Multispecies Household


    It is common for modern households to contain several pets of different species: dogs, cats, rabbits, birds, and others, not to mention the exotic pets that often live in aquaria or other caging that keeps them separate from the household. Questions often arise regarding the behavioral interactions between different species and the best way to maintain a mixed-species household. Unfortunately, this area has not been the subject of much research, so at present, veterinarians must rely on their combined understanding of the principles of learning, normal species-specific behavior, and practical experiences from various multispecies households.

    Predators and Prey

    Safety is a prime issue to consider when pets vary substantially in size or when predators live with prey animals. Dogs are predators and may prey on any other species that might be kept as pets. In addition, large dogs have been known to engage in predatory behavior directed toward small dogs, sometimes fatally. In preying on a small animal, regardless of species, a dog will commonly run at the animal, grab it in its mouth, and give it a vigorous shake while biting hard. Death can result from the crushing of various internal organs caused by the bite or from dislocation and fracture of vertebrae caused by the shaking. This can happen rapidly, and even the presence of humans who try to quickly interfere can be inadequate. Nevertheless, many people successfully keep small prey animals along with dogs, including large dogs, and likewise successfully keep other multispecies combinations, such as cats and rabbits, together under supervision. In all cases, supervising the animals and monitoring their state of arousal and specific behavior is important to prevent undesirable consequences of their having access to each other. The behavior of both the predator and the potential prey is relevant to success.

    Potential Predators

    Dogs that are socialized to other species as puppies may be less likely to view them as potential prey (see "Socialization Classes for Puppies and Kittens," November 2007). In addition, dogs that have been well trained in obedience and that have the calm, relaxed temperament that is a product of regular positive reinforcement training are more likely to be calm and self-controlled around other small animals than dogs that are nervous and highly reactive. Exposing a dog to a variety of novel stimuli while reinforcing maintenance of a relaxed, calm demeanor facilitates the development of a dog that remains calm when exposed to further novel stimuli, including animals it has never seen before.

    Research into the response of cats to various small prey animals has shown that, when cats are raised with specific prey animals, their predatory behavior toward that specific species is usually inhibited later in life. However, this early socialization to prey species is not 100% effective, and cats may not show any inhibition of predation to other prey species.1,2 The converse is also true. Rabbit kittens that are exposed to a nonaggressive cat are more likely to approach a cat at a later age than rabbits that had no early experience with cats.3

    Potential Prey

    The behavior of the potential prey animal can encourage or deter predatory instincts. For example, small or prey animals that run away or squeal may trigger predatory behavior in a dog that would otherwise leave smaller animals alone. At the opposite extreme, some degree of defensive aggression by potential prey may cause a larger predatory animal to keep its distance. While controlled research has not directly addressed this issue, my personal experience with cats and rabbits indicates that a cat is probably more likely to chase and attack a rabbit that is running away from it than a rabbit that is confidently hopping toward it. When I first started keeping house rabbits, my cats were allowed in the same room as the rabbits as long as a human was present and supervising them directly. At first, the cats acted afraid of the rabbits and would make large detours around them rather than chance an encounter with them. This behavior was further enforced when one rabbit, a Polish Dwarf that weighed approximately 2 lb (1 kg), was sitting on a bed. A cat that often rested on the same bed jumped up without having seen the rabbit. The rabbit immediately charged and bit at the cat, causing the cat to jump off the bed unharmed. Nevertheless, the cat was even more cautious of that particular rabbit for several weeks after the incident. Over time, gradual desensitization and counterconditioning of the cat and rabbit to each other has resulted in a relationship in which they can rest quietly less than a foot from each other so long as a human is there. They are not allowed loose near each other when no one is present, as a precaution for the safety of both.

    Cats and Dogs

    Similar scenarios become relevant in interactions between cats and dogs. While a cat that runs away from a dog may trigger a chase by an animal that would otherwise have left it alone, a cat that stands its ground and even hisses or scratches will cause many dogs to keep their distance. In some households, the danger of a dog being harmed by a cat is greater than that of the cat being harmed by the dog. Dogs that persistently charge and bark at cats that actively defend themselves, rather than retreat and hide, may be scratched on the face, including the eye. Again, continued exposure to each other, under supervision, can lead to relationships that range from an uneasy truce to compatible friendliness. Most dogs and cats that are raised together get along well.

    If a dog exhibits any degree of predatory behavior toward a cat in the household, it is essential that the cat have access to safe retreats, even if the owners believe that because of temperament or size, the dog will not actually harm the cat. Creation of a safe haven is usually not difficult, as cats are better climbers than dogs, and easy access to the upper platforms of a cat tree, the refrigerator, or a piece of tall furniture may be all that is needed. A baby gate that the cat can jump but the dog cannot is another option. If the dog is large and the cat is too old or overweight to jump the gate, raising the bottom of the gate to a height of 5 to 6 inches so that the cat, but not the dog, can slip under is another option for the cat to avoid the dog.

    Interspecies Communication

    Differences in communication between species can lead to confusion, even when animals are habituated to each other and do not exhibit any aggression. However, with time and familiarity, many dogs and cats seem to learn to understand each other's signals to some degree. For example, the play bow, in which the elbows are lowered to the ground while the hindlimbs remain standing, is a signal soliciting play that is specific to dogs. When a dog gives a play bow to a cat that is habituated to the presence of the dog but has not learned to understand the play bow, the cat is likely to ignore the solicitation to play. However, after several attempts by the dog to exhibit the play bow and play with the cat, the cat may begin to respond to this signal with a playful interaction. Good judgment needs to be used by humans supervising these interactions. A medium or large friendly dog attempting to play with a rat or a small rabbit can cause substantial harm, even if the dog's behaviors are exclusively playful and nonaggressive. Therefore, when a dog exhibits a play bow to an animal that is likely to be harmed by such an interaction, the owner should call the dog away.

    Interspecies Introductions

    When first introducing animals of different species—for example, when considering adopting a dog into a household that already has cats—the behavior of all the animals involved should be assessed while all the animals, or at least the potentially more dangerous animals, are restrained. A harness or collar, a leash, and possibly a muzzle are all important tools. Basket muzzles can be useful when working with and assessing dogs whose possible response is unknown (see the box ). In all tests and introductions, it is essential that the people handling the animals be calm, experienced animal handlers because any of the animals present are likely to detect fear and nervousness in the humans and respond accordingly. If owners are nervous about handling introductions themselves, assistance from a veterinary professional may be beneficial. However, if any of the animals become anxious in the hospital environment, introductions should not be conducted there.

    The following compatibility test, involving gradual introduction with safety precautions in the initial stages, can be conducted with most species combinations. However, because keeping dogs and cats in the same household is one of the most common multispecies integrations pet owners attempt, the example of a dog"cat introduction is used.

    • To assess whether a dog might be acceptable in a household with a resident cat, begin with the dog on a leash. The cat should be in a crate that allows it to move around and be fully seen, or the dog should have been pretrained to accept a basket muzzle.
    • When the dog is exposed to the cat, with the cat protected by either the crate walls or the muzzle, observe the behavior of both animals carefully. Curiosity and interest are expected from the dog, and the dog should not be reprimanded for exhibiting these behaviors. Ask it to obey commands it knows, such as "sit" and "down." Remaining alert but calm and obeying commands are good signs that the dog may be familiar with cats and not aggressive toward them. If the dog becomes highly aroused and barks or lunges at the cat, it may not be a suitable candidate for living with cats.
    • If the dog has remained calm and obedient, removing the crate or muzzle can be attempted, but the dog should still be kept on a leash. If both the cat and the dog are calm, they should be quietly praised. If the cat runs away or becomes aroused and aggressive, it may need to be desensitized and counterconditioned to dogs, even if the dog is calm, because prey behavior can trigger a predatory response in an otherwise calm dog.


    Keeping different species together, especially when there is a substantial difference in size or a predator"prey relationship in the wild, presents significant risks of harm to the animals that are smaller or natural prey. However, many people enjoy keeping multiple species as pets. Veterinarians can help clients successfully do so by giving them information on appropriate socialization, habituation, desensitization, counterconditioning, and structured training.

    Downloadable PDF


    1. Kuo ZY. The genesis of the cat's response to the rat. J Comp Psychol 1930;11:1-35.

    2. Kuo ZY. Further study on the behavior of the cat toward the rat. J Comp Psychol 1938;25:1-8.

    3. Pongrácz P, Altbacker V, Fenes D. Human handling might interfere with conspecific recognition in the European rabbit (Oryctolagus cuniculus). Dev Psychobiol 2001;39:53-62.

    References »

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