Figure 3. Calcium concentration measurements obtained from fluids collected from the female reproductive tracts ofPeromyscus mice species with naturally varying mating systems. The calcemic content of reproductive fluids collected from the uterus and oviduct did not significantly differ between the polyandrousP. maniculatus (red dots) and its monogamous sister species,P. polionotus (blue dots). The calcium concentration between these regions significantly differed only for P. maniculatus . Small dots denote values measured for individual females; large dots represent the mean values for each species.