The influence of male kittens on the object play of their female siblings.

In a study of domestic cats a sharp increase in playful contacts with objects occurred in most animals at around 50 days after birth. However, this change was not observed in litters that contained only females. Possibly the males by playing a lot had a short-term activating effect on their sisters. In order to examine whether males stimulated their female siblings in this way, the object play of male and female kittens was measured from 42 to 70 days after birth in the presence and absence of their siblings. In the absence of siblings the increase in object play occurred in both sexes at the same stage of development indicating that changes in females were not produced by the short-term stimulating effects of their brothers.