EFFECT OF COLONY SIZE ON INDIVIDUAL ALERTNESS OF PRAIRIE DOGS (SCIURIDAE, CYNOMYS SPP)

From 1974 to 1976, I examined individual alertness of two species of squirrels (Sciuridae): loosely colonial white-tailed prairie dogs (Cynomys leucurus) and densely colonial black-tailed prairie dogs (C. ludovicianus). By observing single adults for 30-min periods and recording various measures of alertness, I investigated the effects on individual alertness of four variables, all of which are directly related to ward (subcolony) size and ward density. Conclusions were based on data from 188 white-tail observations and 280 black-tail observations. Individual alertness consistently correlated negatively with effective increases in ward size and ward density. I discuss various hypotheses that might explain these negative correlations, and conclude that decreased individual alertness is an important benefit of prairie dog coloniality. © 1979.