The changes in the dominance hierarchy over time of a complete field‐captured colony of Cryptomys hottentotus hottentotus

Abstract

The common mole‐rat, Cryptomys h. hottentotus, is a social subterranean rodent occurring in colonies in which one female and one to three males are involved in reproduction and the remaining colony members are non‐reproductive. Within each sex the reproductive animals are usually the largest and most dominant animals.The dominance hierarchy amongst a field‐captured colony was linear (h = 0.95, calculated from Landau's linearity index) soon after capture. The non‐reproductive females were ranked low in the dominance hierarchy; many were subordinate to non‐reproductive males. The order of capture of mole‐rats was not related to the position in the dominance hierarchy. The hierarchy became non‐linear (h = 0.56) after six months in captivity during which two juvenile animals became adult. The breakdown in the hierarchy may result from the lack of opportunity in captivity for animals to disperse and establish satellite colonies, or from colony members becoming co‐dominant in the hierarchy as a result of a rise in rank by young animals.Dominant mole‐rats are involved in a greater proportion of interactive behaviours than subordinates. Popularity studies show that females tend to be more popular animals than males. The largest reproductive male was the least popular animal in the first study, whereas a beta male was the least popular animal in the second study period. The reproductive female was the most popular in both periods.