Free-living cats do form social groups and female kinship has been suggested as the basis for group formation. The groups typically consist of females, usually related, and their offspring. The males have two tactics. Some have ranges that overlap several groups of females while others have affiliation with one group and return to the group site. More recent data show that there are 'central males' that stay around the resources of the core area and 'peripheral males' that have access to resources but roam widely.

There are several benefits to being social, such as shared maternal care of offspring, concentration of potential mates and improved defence of food resources. It has been shown that cats engage in non-random close proximity that is independent of location and which is indicative of a strong social bond. Adult cat dyads (pairs) spend time within 1 metre more often than would be expected by chance. These dyads are referred to as preferred associates.

Social grooming is also known as allogrooming. It has been documented in 44 species of free-living primates, dairy and beef cattle, kangaroos, deer, antelopes, equids, canids, felids and rats. The benefits of allogrooming include care of the body surface, parasite removal and wound care, provision of extra nutrients (e.g., salt), regulation of social tension and reconciliation. It has been shown that the function of allogrooming is social in nature as opposed to purely hygienic. Allogrooming promotes cohesiveness and persistence of groups and reflects an already existing bond. Lions allogroom as part of mating, in mother-young interactions and in social situations.

The adaptive consequences for the 'groomee' are obvious but it is less clear what the benefits for the groomer are. Sociobiological altruism is a possibility. If the groomer and the receiver are related, the behaviour could derive its adaptive value from indirect benefits, namely, its contribution to the inclusive fitness of the groomer, and it could be promoted by kin selection.

Allogrooming in cats is seen between mother and young and serves a utilitarian function to maintain cleanliness. It is also part of mating behaviour. Allogrooming has also been observed to occur between intact adult cats that were not mother-offspring pairs, or as part of mating (all gender combinations). Studies show that cats spend 15% of their day (3.6 hours) engaged in grooming behaviour, and there is no evidence showing that a solitary cat is any less clean than a cat that is groomed by others.

In 2001 we conducted a study to look at the effect of relatedness and familiarity on affiliative behaviours, specifically proximity and allogrooming in the domestic cat. The hypotheses were that:

 Cats would spend significantly more time in proximity to kin than non-kin

 Cats that have already spent some time together, i.e., who are more familiar with one another, would spend more time together

 Cats that have relatives would engage in allogrooming behaviour with relatives more than with non-relatives

 Cats that are more familiar with each other would be more likely to allogroom each other than cats that are less familiar with each other

The research colony consisted of 16 males and 12 females and 15/28 had one or more relatives. There were five genealogies represented. All of the cats were neutered. The study site was a private dwelling in Athens, Georgia, USA where the cats had free access to certain indoor areas and to the outside in a protected fenced-in area.

Data were collected from 17/9/01 to 25/10/01 and from 5/11/01 to 18/12/01 using focal animal sampling (15 min/cat) and instantaneous sampling. Per cat there were 14 focal samples with 8 instantaneous scans per sample at 2-minute intervals resulting in 112 point samples per cat. There was a total observation time of 3½hours per cat. All instances of allogrooming behaviour that were observed during this study, and for 6 additional months as part of a subsequent study, were recorded.

The hypotheses were verified. Cats with relatives spent more time in proximity to relatives than non-relatives and cats that were more familiar with one another spent more time together than with cats that were less familiar. Relatives and cats with whom the focal cat was more familiar were more likely to be within 1 metre than non-relatives and cats with whom the focal cat was less familiar; however, relatedness had more of an effect than did familiarity. Cats with relatives groomed relatives more than non-relatives and cats that were more familiar with each other groomed each other more than cats with whom they were less familiar. On average, those cats that had relatives groomed a relative 11 times more than they groomed a non-relative.

Study Relevance

Cats are often relinquished to animal shelters because of aggression to other household cats. There is an inverse relationship between the length of time cats are together and the aggression rate. The results of our study show that there is a direct relationship between the length of time that cats are together and the rate of allogrooming and proximity, so it is wise to counsel owners to have patience. Also, adopting a related litter, a set of siblings, a mother and siblings, or even unrelated kittens of the same age, may result in higher rates of affiliative behaviour and stronger bonding than periodically adopting single, unrelated adult cats.