A general approach for calculating the likelihood of dyadic interactions: Applications to sex preferences in rat pups and agonistic interactions in adults

We introduce a general approach for calculating the expected frequency of different types of dyadic interactions between animals and illustrate it with two applications. The first application determines whether there are sex contact biases between male and female Norway rat pups. We hypothesized that opposite-sex contact biases should be small, because it is likely that differences in contact based on the sex of animals would interfere with other biological functions, such as group temperature regulation. We found a small but significant bias of 3% in opposite-sex contacts. The second application reanalyzed J. B. Calhoun’s (1962) data on antagonistic encounters between rats for two factors (sex and birth location), each with two levels. The results of these two applications suggest that sex contact biases among pups are predictive of agonistic encounters among adults and that this approach has general application to the analysis of dyadic interactions among animals.