Individual odors of rats are discriminable independently of changes in gonadal hormone levels.

Male Long-Evans hooded rats were tested for their ability to discriminate between the urine odors from individual outbred Long-Evans rats using the habituation-dishabituation method. There were discriminable differences between the urine odors of two individual intact males, castrated males, estrous/proestrous females, diestrous/metestrous females and ovariectomized females. Thus, individual outbred rats of both sexes can be discriminated on the basis of their urine odors using this technique and discrimination between individuals occurs despite changes in gonadal hormone levels. This suggests that individual recognition is independent of reproductive state and social status although these may influence the production of body odors used for individual discrimination in rats. Individual odors most likely reflect genetic differences between individuals within the outbred strain.