Figure 3 .
Swelling size in relation to the timing of ovulation: a) the close agreement between measures of swelling height and width; b) the difference in swelling height between conceptive and non-conceptive cycles. The grey shaded area represents a presumed four day fertile period that incorporates the two-day ovulation window.
Higham et al. BMC Evolutionary Biology 2012 12:89 doi:10.1186/1471-2148-12-89