Ask The Biologist

Hello Ladies!

Hello Ladies!

By Bob Humphrey

QUESTION: We have an abundant supply of whitetails on our Kansas acreage and enjoy their company immensely. As expected, there appear to be far more does than bucks. Allowing for the fact that hunting regulations favor the harvesting of bucks, I can find no data on the likelihood of a doe giving birth to a male vs. female fawns. Is what I am witnessing simply the normal social order in that if an area has too many bucks for the available doe population some bucks migrate elsewhere? Or are more female offspring born than male? - Richard W.

ANSWER: First, what you're witnessing is not unusual. In fact, observations of skewed sex ratios are quite common, and there are several reasons why.

First, most observations occur in the fall, during hunting season, when does and fawns tend to be more viewable.

Second, hunters often fail to distinguish the sex of fawns and consider all antlerless deer to be does (underestimating the sex ratio of this age class by 100 percent).

Third, as you suggested, where most hunting pressure is directed toward bucks, sex ratios can be skewed toward does.

However, the biological maximum sex ratio you can achieve in free-ranging deer is roughly 5:1. Even with no doe harvest, a certain number adult does die each year from old age, vehicle collisions, disease, predators and other natural causes. Meanwhile, the sex ratio of fawns born each year is about 50:50. The sex ratio of a post-hunt population might be more highly skewed, but annual recruitment provides a correcting factor that always brings things back in line.

There have been several studies on whether birth sex ratios might be skewed in very stressed or very healthy populations, but results are conflicting. In either case, the effect would still be minimal.

For the second part of your question, yearling buck dispersal is also a normal phenomenon that occurs regardless of sex or age ratios. However, once a buck reaches age 2, he seldom leaves his home range for more than a day or two.

If does are scarce he might wander more, and more often, to seek them out, but he typically returns home. In populations with lots of available does, a buck is less inclined to wander, although aggressive encounters might limit which bucks get to do most of the breeding.

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Copyright 2020 by Buckmasters, Ltd.

Copyright 2020 by Buckmasters, Ltd