In mammals, the XX/XY sexual determinism is very conserved but some rare species escape this rule. The small African pygmy mouse Mus minutoides is one of these species, presenting a new sexual determinism. In this species, a sexual inversion exists and is due to a mutant X chromosome, the X* chromosome which feminizes the individuals. Then, there are XX, XX* and X*Y females and XY males in M. minutoides population. This sexual inversion leads to phenotypic differences between genotypes: X*Y females are for example more aggressive and less anxious, i.e. masculinized, compared to other females. However, at present, few studies have investigated the physiology and even less the influence of the sexual genotype on it in this species. The objective of this project is to continue the phenotyping of M. minutoides by performing behavioral and physiological measurements (from the whole animal to the cell).