Long term changes in nest condition and pup grouping following handling of rat litters

Observation of rat litters over the entire preweaning period revealed long term changes to result from handling pups. Handled litters had fewer good nests and were less likely to be found in a single group than control litters. These differences are not attributable to the disturbances per se, as litters where the mother was removed did not differ significantly from undisturbed controls. The differences occurred predominantly in the daytime when maternal activity was at its lowest.