Free-ranging, domesticated male farm cats often have larger territorial ranges than female cats do, on average three times as large.⁴ So a male pet cat may require more space than a female cats does, and this effect may be multiplied in groups. However, most studies examining space use in pet cats are done with cats that have outdoor access, and in these studies, both male and female cats demonstrate range overlap with other cats. A study of indoor-only cats showed that in a 10-room house male cats usually have a larger range (four to five rooms) than their female counterparts do (three to 3.6 rooms) but that the cats often share favored spots on a rotational basis.⁵ A 2,000-sq-ft house with multiple feeding locations, vertical perches, and litter boxes may be able to successfully accommodate four or five cats, while a house with the same square footage but with limited provisions may only be able to successfully accommodate two cats.

Some owners wonder which gender would be best when adding another cat to the household. A study of indoor-only neutered two-cat households showed that gender (male-male, female-female, male-female) pairings did not affect affiliative or aggressive behaviors.⁶

8. AN HOUR OF SOCIALIZATION IS WORTH A DAY OF CONSULTATION

The sensitive socialization period is the period in an animal's life when it is sensitive to and develops social interactions with others. From a human-animal bond perspective, it is desirable that kittens develop social attachments to their owners. Studies have shown that the sensitive socialization period in kittens toward people is between 2 to 7 weeks of age.⁸ In these studies, the researchers exposed kittens of different ages to handling by people for different durations. The kittens were then tested on their approachability to people, the time willingly spent on people's laps, and other affiliative behaviors toward people (flank rubbing, chin rubbing, vocalization). The researchers found that cats that were handled between 2 to 7 weeks of age were friendlier to people.

Other studies have found that one hour of handling by people per day provides the maximum beneficial human-socialization effect; beyond that hour there is little additional benefit.⁹ If handled exclusively by one person, a kitten may develop a special relationship with that person but still appears to be able to generalize this human socialization to other people.⁹ A study testing single-handler kittens vs. multiple-handler kittens found no difference in holding scores.⁹

A study performed in the United Kingdom examined the effects of socialization on feral kittens.¹⁰ The researchers examined 70 kittens of feral origin (born outside of human habitation to an unowned queen) and 28 domestic kittens (born in a home or shelter to an owned or recently owned queen). At different ages, the kittens were exposed to different levels of handling and social contact with people. At 1 year of age, the kittens were tested on the length of time they would stay on their owners' laps with light restraint and on how quickly they would engage in play with a toy. Also, the owners were questioned about their satisfaction with their pets and asked to report any problem behaviors they experienced with their kittens, such as housesoiling, furniture scratching, or fear of people. Twenty-three of the feral kittens had received no handling or contact with people before 7 weeks of age. When tested at 1 year of age, 11 of these 23 kittens could not be held by their owners for one minute. Both the feral and domestic cats played with the object toy, showing no differences between the groups. However, the feral kittens that were raised indoors only were faster to play with the toy than those raised in an outdoor pen.