play fighting

Journal of zoology

In many mammals, play is one of the most conspicuous behaviors during early development, but with notable inter‐individual variation even within the same litter. We investigated predictors of such variation in the Eurasian lynx ( Lynx lynx ), with a focus on potential effects of cubs' early body mass on the frequency of initiating play. We studied 45 cubs from 18 litters, kept in enclosures together with their mother. Observations started when cubs began to leave the natal den (around postnatal day 30) and lasted until weaning (around postnatal day 90). Individual differences in play were consistent over time, across all cubs as well as among littermates. The initiation of different play categories – with siblings, with the mother and solitary play – was positively associated and showed a similar developmental pattern. Cubs' body mass was positively associated with the frequency of play events; heavier cubs initiated play more often than lighter ones. This is consistent with the surplus resource theory, that is, that heavier young might have more energy resources available to allocate to play. Alternatively, lighter cubs may have initiated play less often to avoid asymmetrical rough‐and‐tumble interactions with their heavier siblings. Additionally, we found that offspring from middle‐age mothers initiated play more frequently than offspring from younger or older mothers. As cubs from middle‐age mothers had higher growth rates, this finding is again consistent with the surplus resource theory. Important questions for future research are whether such stable individual differences in play during early development correlate with other behavioral traits and translate into individual differences in behavior in later life.

Predictors of individual differences in play behavior in Eurasian lynx cubs