“The Effects of Litter-Size Variation on the Development of Play Behavior in the Domestic Cat: Litters of One and Two”, 1988-02 ():
In many litter-bearing species, litter-mates interact with each other in a variety of ways during early life. In the domestic cat, Felis catus, social play is a prominent form of interaction between litter-mates.
The present study investigated how the lack of a litter-mate affected the development of kitten play and of the mother-kitten relationship. The subjects were 14 litters of domestic kittens living with their mothers in large indoor cages. 7 litters contained two male kittens, and the other 7 contained single male kittens. Social interactions within the families were observed from day 22 to day 83 after birth.
Single kittens played a more active part in maintaining close proximity to their mothers and directed more playful behavior at them than did kittens with a sibling. Although single-kitten mothers avoided their offspring more than did mothers of litters of two, they also directed much higher levels of play behavior at them.
Despite the marked difference in the mother-kitten play relationship in the two litter types, single kittens experienced quantitatively less social play than did kittens with siblings. As the kittens grew older, single-kitten mothers showed higher levels of aggression towards their young than did mothers of litters of two.