A comparative study of different populations of Mus musculus domesticus: emotivity as an index of adaptation to commensalism.

1. Emotivity is assessed by the amplitude of the corticoadrenal response to a novelty stress at three different seasons. 2. Commensal and outdoor populations of the house mouse are compared. 3. Outdoor mice display on one hand, lower mean levels of standard corticosterone, and on the other higher amplitude of response to the novelty stress when compared with the commensal mice. 4. Results are discussed in terms of divergent adaptive strategies of mice in respect with their social environment. 5. We underline the originality of the Robertsonian commensal population which displays a particular strategy consisting of a mix of outdoor and commensal traits.