Fetal aging sounds like a technique used by Ob/Gyn doctors and ultrasound technicians, but deer managers can learn a lot about the population they’re managing by taking some annual fetal measurements.
Joe Hamilton, QDMA’s founder, led a research project from 1979 to 1983 that ultimately developed the fetal-aging criteria and scale that deer managers throughout North America still use today.
A simple bar chart works well, and you plot the number of pregnant does in your harvest data (the sample size) on the vertical axis.
Plot the conception dates on the horizontal axis and group them on a weekly basis.
For example, in Pennsylvania peak breeding generally occurs between November 10 and 20, but Game Commission conception data shows breeding routinely occurs in October.
If you don’t have a scale, store the fetus(es) in the freezer for analysis at a later date. Place fetus on the fetal scale in a natural position with the forehead at the left edge and the back parallel to the top edge of the scale. Locate the line closest to which the extreme end of the rump falls. Use average length with twins or triplets of different sizes. There are five sets of measurements on the fetal scale. The procedure for determining date of birth is similar, except days to birth (as measured on the scale) are added to the Julian date noted in No. Let’s say you harvested a doe on December 15, and you determined the age of the fetus was 51 days.