Urine-marking and the response to fresh vs. aged urine in wild and domestic Norway rats

Wild and domestic Norway rats (Rattus norvegiens) were compared in regard to their tendency to investigate the odors of fresh vs. aged rat urine and to urine-mark metal rods and wooden blocks placed in their home cages. Castration, sex, and domestication had no effect on the tendency to investigate sources of fresh vs. aged urine odors, but the odor of aged urine was more attractive than fresh urine for most subjects tested. The frequency of urine marking was lower for females and castrated males but generally did not differ between wild and domestic stocks. The implications of these findings for the ecology of the species are discussed.