December 11, 2017
Spring is when yearling deer decide to make your property part of their adult home range.
Recent studies done by Penn State, and older studies in various other parts of the country, have gathered data on how and when young deer disperse from where they were born to new adult home ranges.
In these studies, young deer and their movements were tracked via radio collars, showing that most year-old male deer and anywhere from 8 to 25 percent of female deer disperse away from the area they were born and set up a new home range, typically many miles away.
Scientists believe that dispersal of young animals in mammal populations reduces inbreeding.
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It is likely that in whitetails a much higher percentage of males disperse than females because females raise the young and the better the doe knows her home range, the higher the survival rate of her fawns.
Almost all female yearlings disperse in the spring. You might think that young males would be pushed out of their birth range in the fall breeding season, but a significant number of males also disperse in the spring, in May or June — about the time that older does are dropping their fawns.
Does about to give birth tend to want to isolate themselves, and they want access to good habitat for their new fawns. Dominant does become more territorial, and more apt to "push" younger deer out of their range.
As you might expect, there's a strong correlation between deer density and young doe dispersal rates: the denser the deer population, the more likely it is that yearling does and bucks will disperse.
The studies suggest that space itself is important for a dominant doe about to give birth, but do not directly assess what is likely another factor at work: the quality of habitat.
Since dispersal occurs during the fawning season, deer dispersal rates seem dependent on the quality of spring habitat.
If this is true, then for anyone managing deer property who wants to discourage their deer from leaving (or to encourage off-property dispersing deer to make this property part of their adult home range) spring habitat work is critical.
The first thing to note, however, is that probably no matter what you do, most of the yearling bucks on your property are going to leave. They are born to go establish their own territories away from does that they are closely related to. It's what they do.
While you may not be able to make your property larger, you might be able to increase its carrying capacity: Rather than one central area of habitat that is good for fawn-raising, multiple areas separated from each other may hold more mature does.
A number of spring food plots near separate bedding and fawn-raising cover might reduce the competition for "space" among does, and give young deer looking for a new home range more reason to stop at your property.
If you have been concentrating most of your food-plot work on fall plots, it might be a good idea to start planning now to make more use of spring food plots, especially if you are interested in increasing the number of deer on your property.
If you have quality deer on your property already, such spring food plots might slightly decrease the dispersal rates of button bucks that are offspring of your better bucks.
Dispersal rates of yearling males is always high — 50 percent was the lower found in the Pennsylvania study — and it can be as high as 75 percent. But there's a chance that your spring habitat work can affect how many young bucks from other places elect to stay on your property through their adult years.
Also, the study suggests that if you see a year-and-a-half-old buck on your property at the end of the hunting season, there is a 90 percent chance that he will survive and that your property will always be part of his home range.
If he doesn't get shot when he's young, he might grow into a buck worth taking — and he'll be on your property at least part of the time.
A couple of other facts are indicated by the Pennsylvania study: male yearlings that dispersed traveled an average of 5 miles from where they were born.
Although fewer females disperse, those that did averaged 11 miles. Female deer travel farther not only as the crow flies, but take longer to do so — they may spend two weeks looking for a place to "set up."
Also, both male and female dispersal was affected by roads and rivers. Of course, deer can and do cross both roads and rivers, but the radio collar studies showed that deer will often stop rather than cross such barriers, or change direction and move parallel to them. Roads did not have to be Interstate Highways, either: even paved county roads had some influence.
If you have such a barrier on a boundary of your hunting property, habitat work near it may encourage dispersing deer to stop on your hunting land rather than cross the barrier and go off your property
The study also implies that in areas with high deer density, taking a few does is unlikely to reduce the number of deer on your property — if 50 percent of the doe yearlings and 75 percent of the yearling bucks are leaving anyway, then removing a doe is likely to result in lower dispersal rates first rather than fewer deer.
Conversely, in areas with low deer density and low dispersal rates, not shooting a doe — especially a young doe — means you have a better chance of seeing her on your property for years to come.
To get more insight into deer movements and what their implications are, do an internet search for "Penn State deer-forest study."