SOCIAL AND ENVIRONMENTAL-FACTORS MODULATE THE LEARNING OF PINE-CONE STRIPPING TECHNIQUES BY BLACK RATS, RATTUS-RATTUS

Black rats inhabit Jerusalem pine forests in Israel, where they nest i n the trees and feed on the seeds extracted from the pine-cones. The r ats obtain the seeds by systematically stripping the cone's scales in a spiral pattern, using a sequence of stereotyped behaviour patterns t ermed the spiral technique. This stripping behaviour is culturally tra nsmitted from mothers to their pups. Adults do not learn this task cul turally, and only a few adults require it spontaneously even under fav ourable conditions. Experiment 1 tested whether the age of separation from the mother, sex of the pups, litter size and age at first exposur e to cones affected the pups' stripping ability. Only the age of separ ation from the mother affected the proportion of pups that learned to strip cones; litter size, sex or age when pups were exposed to cones h ad no affect. Under laboratory conditions pups obtained pine seeds by using a second technique, termed shaving, which required a greater ene rgy expenditure than the spiral technique. Experiment 2 tested whether the age at which pups were first exposed to cones influenced the type of stripping technique which they would acquire. Most pups (76%) expo sed to pine-cones since birth used the shaving technique, and most pup s (68%) exposed to pine-cones from age either 20 or 30 days developed the spiral technique. A third experiment examined whether developing p ups can learn to strip cones when exposed only to mature brown cones, which are woodier and tougher than the green cones. None of the pups t hat were exposed only to brown cones learned to strip cones, even foll owing exposure to cones for 80 days. (C) 1996 The Association for the Study of Animal Behaviour.