ONTOGENY OF PINE-CONE OPENING BEHAVIOR IN THE BLACK RAT, RATTUS-RATTUS

In recent years black rats have occupied a new habitat: the Jerusalem pine, Pinus halipensis, forests in Israel. Their sole source of food in these forests is pine seeds, which can be obtained from the cones only by a complex feeding technique. This study investigated the ontogeny of the pine cone opening behaviour and the transmission of this behaviour from one generation to the next. Adult black rats were unable to attain the technique through trial and error, and only gnawed randomly on the cones in an energy wasteful manner. Pups, but not adults, were able to learn the technique by observing experienced rats opening the cones. The flavour of the mothers' milk was eliminated as a possible cue in influencing the pups' acquisition of the opening technique. Cross-fostering pups born to 'naive' mothers on experienced mothers and vice versa indicated that the technique of pine cone opening is not transmitted genetically but, rather, through a process of social transmission. In a final experiment naive adult rats were exposed to pine cones with consecutively decreasing numbers of previously stripped rows of scales. The majority of the rats that were exposed to such partially open cones did learn to strip pine cones. It is argued, however, that passive exposure to partially stripped cones is unlikely to occur in the natural environment. © 1992.