A variety of prey species are able to detect predators by odours emanating from their urine, feces, fur and anal glands. However, it is unknown whether the odour of a predator’s blood also contains information signalling “predator” to a prey. The aim of the present study was therefore to assess if blood odour from a cat elicits avoidance or anxiety responses in CD-1 mice (Mus musculus). A two-compartment test arena was used to assess place preference, motor activity and fecal excretions when the mice were simultaneously presented with cat blood and a blank control. Additionally, the mice were tested with horse blood and N-pentyl acetate, a fruity odour. The mice did not show avoidance of any of the three odours. Nevertheless, the mice were significantly less active when exposed to cat blood in comparison to horse blood, but did not increase defecation when exposed to cat blood. This suggests that the information mice get by the odour of cat blood did not contain the signal “predator”.

It is essential for prey species to be able to detect predators to avoid them. The sense of smell is used by a number of prey species for this purpose. The aim of the present study was to assess if one of the odourants that make up a predator odour is sufficient to induce a behavioural response in mice (Mus musculus). Two predator odourants were used, 2,2-dimethylthietane and methyl-2-phenylethyl sulfide, which are both found in the secretions of natural predators of mice. An odourant found in fruits, n-pentyl acetate, was also used. All three odourants were presented at a concentration that was a factor of 100 above the olfactory detection threshold of mice. Ten adult predator-naïve CD-1 mice were individually put in a two-compartment chamber one of which contained an odourant while the other contained a near-odourless solvent (diethyl phthalate). The results indicated that methyl-2-phenylethyl sulfide was actively avoided by the mice. Towards 2,2-dimethylthietane and n-pentyl acetate, in contrast, the mice behaved indifferent. Further, the results suggest a significant correlation between the number of switches between the two compartments of the test chamber and the test sessions when the animals were presented with n-pentyl acetate, but not when they were presented with the predator odourants. The results support the notion of an innate fear response towards the predator odourant methyl-2-phenylethyl sulfide in mice, but further studies with more animals and different concentrations of the odourants are necessary.