A relationship between frequency of display of territorial marking behavior and coat color in male Mongolian gerbils

Mongolian gerbils exhibit a territorial marking behavior which is androgen dependent and sexually dimorphic, with males marking more frequently than females. In males a subpopulation of high frequency and low frequency markers was observed in gerbils with brown or black coat color. The present study examines the possibility that this marking frequency difference is genetically determined. After eight generations of selective inbreeding of brown gerbils to maximize the incidence of high marking males, no change in the ratio of high to low marking males was observed. When less common black gerbils were mated with brown gerbils in classic F1 X F2 crosses, a ratio of 3 brown to 1 black resulted, suggesting that black coat color was a Mendelian recessive trait. Marking behavior measured in the offspring of F1 X F2 crosses over five generations revealed significantly higher average marking frequencies in black males than in heterozygous or homozygous brown males. This difference was due to a smaller percentage of low markers among black males than among brown males. Females from these crosses showed no marking frequency differences. Plasma testosterone levels and ventral scent gland size were not different among low or high markers in either black or brown males. These results suggest that there is an androgen-independent genetic component to the expression of territorial marking behavior in the gerbil.