Aversive and attractive marking of toxic and safe foods by Norway rats

The present series of studies was undertaken to investigate the hypothesis (von F. Steiniger, 1950, Zeitschrift für Tierpsychologie, 7, 356-379; K. A. Stierhoff, & M. Lavin, 1982, Behavioral and Neural Biology, 34, 180-189) that rats poisoned after eating a novel food will mark that novel food in such a way as to dissuade naive conspecifics from ingesting it. Our results provided no evidence of aversive marking of a novel food by rats poisoned after ingesting it. We did, however, find evidence of attractive marking of feeding sites by rats exploiting those sites. This attractive marking rendered exploited feeding sites more attractive to naive conspecifics than other portions of an enclosure that rats had visited. The present findings are consistent with the results of a number of experiments conducted in our laboratory over the last decade indicating that rats directly communicate learned food preferences, but not learned food aversions.