Territoriality and the Influence of Females On the Spacing of Males in the Cockroach, Nauphoeta Cinerea

Abstract

Abstract(I) The first aim of the study was to extend earlicr observations on the effect of density on social structure and in particular to see if all males in a group became territorial at very low density. The second aim was to determine the social organisation of females in relation to territorial males. (2) Most males were observed to become territorial at very low density but there was a definite limit to the tendacy to spread out. A few males were not territorial and the behaviour of these animals is described. (3) The females formed a group, usually but not always, on a male-occupied territory. Unreceptive, virgin females introduced into the observation tank remained inactive for the first few days. In these females activity and exploration were correlated with the onset of receptivity. Some females mated at this time and then moved on until they joined the female group. Others joined the female group immediately and mated with the territory owner if one was present. Once females had joined the group they did not leave except for brief sallies or to give birth to their young. The female group did however move en masse and sometimes moved the entire length of the tank. (4) One of the most obvious effects of the females was on the pattern of male territory holding. Competition for territory centred round the female group and several males took up residence with the females during the day. Either one of these males became a despot or a hierarchy of dominance developed. At night the top-dominant chased the others off his territory. These males, with the exception of a few very low-ranking males, then set-up territories on adjacent rest-sited and made occasional attempts to rejoin the female group. This sequence of events was repeated each day. (5) The second obvious effect of the females was on the amount of fighting. Males were alone more often than they were with females but when females were present there was more fighting. (I) The relationship between hierarchy and territory is discussed and conclusions are drawn about the function of territory and the limitations of the territorial system in Nauphoeta.