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Compendium February 2007 (Vol 29, No 2)

Understanding Behavior: Environmental Enrichment for Indoor Cats

by Terry Marie Curtis, DVM, MS, DACVB

    There is an ongoing debate about whether cats are happier indoors or outdoors. In general, indoor cats are healthier because they are not subject to risks associated with predation or trauma (e.g., hit by car). However, is there a downside to keeping cats indoors all the time? If so, what is it? One of the primary arguments against keeping cats indoors is that they can become unhappy and bored, but this is unfounded.

    Nevertheless, to ensure that indoor cats are adequately stimulated, the cat's environment should be assessed. Is the environment under- or overstimulating? Each case is different, but there are some general considerations. Enrichment involves physical, social, and temporal complexity (i.e., the degree to which the stimulation changes, introducing novelty and variability into the cat's surroundings). Enrichment addresses variety in the structural, visual, auditory, olfactory, and gustatory stimuli in the environment.

    To recognize the role of enrichment in indoor cats, it is important to know what cats do normally. In a field study by Panaman,1 five female cats were observed for 360 hours. Each cat was observed for all behavior classified under seven categories: sleeping, resting, hunting, grooming, traveling, feeding, and other behaviors. The cats slept for 9.5 hr/day (39.7% of the total time), rested for 5.3 hr/day (22.2%), hunted for 3.6 hr/day (14.8%), groomed for 3.5 hr/day (14.5%), traveled (moved without hunting) for 0.6 hr/day (2.7%), ate for 0.55 hr/day (2.3%), engaged in other activities for 0.33 hr/day (1.4%), and were out of view for 0.58 hr/day (2.4%). Therefore, veterinary recommendations for enriching an indoor cat's environment should be based on typical behavior patterns of free-ranging domestic cats.

    Sleep and Rest

    Based on the results of the Panaman1 study, the typical cat can be expected to sleep and rest for approximately 15 hr/day. (This is no surprise to those with cats!) One consideration in enriching a cat's environment is that cats are crepuscular (i.e., more active in the early morning and the evening). This can result in cats awakening owners in the early morning and/or the middle of the night. If a cat is awakening its owner by begging for its breakfast, this can be avoided by free-choice feeding or by providing a mid-night meal from a timed feeder. Owners can also try increasing the cat's playtime and feeding a satisfying snack before bedtime.

    Owners should have various places designated for their cats to rest. It is important to provide places for cats to just "hang out" (e.g., perches, rugs, chairs, an extra bed, boxes, cat hammocks and "condos"). If the household has more than one cat, it is important to have a variety of places where the cats can isolate themselves from each other, if necessary.


    Grooming constitutes almost 4 hours of a cat's day. Cats groom as part of normal maternal behavior, coat care, and ectoparasite removal, but the most important function of grooming may be social interaction with other cats and owners. Indoor cats that do not have a companion cat to groom them often rely on their owner for this type of social interaction. Several types of brushes and combs are available, including high-tech cat spas for pampered cats. Not all cats like to be groomed and petted by people, and some cats may have petting intolerance. Therefore, it is important to watch for signals (e.g., ears back, tail swishing, stiff body posture) that a cat is going to strike. Cats tend to groom each other on the head and neck, so it is a good general rule for people to concentrate their petting and grooming on these areas, especially for cats with petting issues.


    Outdoor cats hunt for almost 4 hr/day. If all of a cat's food is available in a bowl, there is not much need to hunt. Owners can reward their indoor cat's hunting endeavors by putting all or a portion of the cat's food in puzzle toys, bowls that are on an elevated surface so that the cat needs to jump up to get the food, and/or hidden bowls that the cat has to find. This can be particularly helpful in encouraging overweight cats to move. In general, it is desirable for owners to provide indoor cats with a "land of plenty": several food and water bowls with a variety of types of food. There are numerous types of bowls, automatic feeders, and water fountains to choose from. The idea is to make food seeking a fun activity. From personal experience and from talking to clients over the years, it seems that many cats prefer to drink in places separate from where they eat. Providing bowls of various shapes can help encourage indoor cats to drink the fresh water they need.


    Traveling constitutes almost 50 min/day of an outdoor cat's time. Providing ramps, stairways, and other climbing opportunities can help address this need in indoor cats.


    Play can be considered disorganized hunting behavior, and a portion of the time that the cats in Panaman's study1 spent hunting and traveling could certainly have been considered play. If an indoor cat gets along with other pets in the household, it is likely to play with them. However, because not all cats that live together play with each other, it is important for owners to play with their cats. The owner's imagination is the only limitation to finding appropriate cat toys. The trick is to find the type that the particular cat likes. Some like balls, others like furry mice, and others like anything that moves on a string. Most cats love the Panic Mouse (Panic Mouse, Inc.), which can provide interactive, random play.


    Scratching is a normal feline behavior that loosens old nail layers and sharpens the claws. Scratching also provides visual and olfactory signals to other cats. Cats can have specific preferences for scratching substrates. In general, when trying to shape a cat's scratching behavior so that it uses a scratching post or mat and leaves the sofa alone, there are two goals. The first is to make the acceptable scratching surface desirable to the cat. The substrate can be sprinkled with catnip and should be put in a location that the cat likes. A choice of substrates should be provided, including vertical (e.g., scratching posts) and horizontal (e.g., scratching mats or pads) options. The second goal is to make the unacceptable scratching surface undesirable to the cat. Various motion detectors and smelly sprays are available. A particularly effective tool (based on personal experience) is Sticky Paws, which is a nontoxic, double-sided tape that is easy to apply and remove. Sticky Paws (stickypaws.com) can be used on furniture, countertops, stereo speakers, drapes, and carpets. A product called Soft Paws (softpaws.com) can be an effective alternative to declawing. Soft Paws are vinyl nail caps that can effectively cover a cat's nails so that no damage occurs when the cat scratches furniture, drapes, or other surfaces.

    Visual, Auditory, Olfactory, and Gustatory Stimulation

    Because cats need visual stimulation, indoor cats should have access to windowsills or "window seats" to watch birds, squirrels, and other outdoor activities. Some cats also like to watch videos of birds, fish, and bugs. An aquarium or fishbowl can also be entertaining, but owners should ensure that the fish are safe.

    Cats also need auditory stimulation, so they should be given toys that make noise. A favorite of many cats is a ping-pong ball in a bathtub.

    For olfactory stimulation, nothing beats catnip (Nepeta cataria). Not all cats respond the same way to the same kind of catnip, so owners may have to try different kinds to find the right one. Catnip comes in various forms, including the fresh herb, catnip "bubbles," and the traditional stuffing in various toys. The dried herb can be sprinkled onto a towel or throw rug on which the cat can rub and roll. As with any other herb, catnip loses its aroma over time, so owners should periodically refill or replace catnip toys.

    Anyone who has an indoor cat that has inadvertently gotten outside has probably seen the cat chew on grass, which provides both olfactory and gustatory stimulation. "Legal" edibles such as fresh cat grass and catnip can be healthy alternatives to houseplants. Cat grass is usually a mixture of soft grasses, such as wheat, oat, and barley. A favorite of mine is Cosmic Kittyherbs. For best results, the seeds should be planted in large terracotta pots. The grass takes several days to grow and then lasts for 2 to 3 weeks.


    To design an indoor "paradise" for cats requires imagination and an understanding of normal cat behavior. Hundreds of resources are available, but it should be remembered that what is expensive and appealing to humans is not necessarily what a cat wants. Many cat owners have told me that their cat's favorite toy is a milk-bottle cap, twist tie, or hair tie. Other homemade toys include wadded-up paper and empty paper bags. The goal is for everyone to have fun-the people and the cats!

    See information on Resources for Feline Environmental Enrichment .

    1. Panaman R: Behavior and ecology of free-ranging farm cats (Felis catus L.). Z Tierpsychol 56(1):59-73, 1981.

    References »

    NEXT: Web Sights (February 2007)


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