Ask The Biologist

How big is my herd? Let me count all the bucks and does.

QUESTION: In a story in the October, 2016 issue, the topic was what kind of social structure exists in whitetail herds. I would like to know how big a herd can be that includes all the groups of bucks and does within a herd’s territory. — Ricky W.

ANSWER: I’m not sure there really is an answer to your question since there are so many variables.

First, you might recall there was a sidebar in that story explaining that deer do not actually have territories. Instead, they have a home range, which is defined as where an individual spends 90-95 of their time over the course of the year.

Second, the story also explained dispersal differences between bucks and does. Does often disperse in what is termed the “rose-petal effect,” where the home range of a doe’s offspring is adjacent to and slightly overlaps its mother’s. If you were to plot the home ranges of successive generations on a map they might look something like a rose, with the original maternal doe in the center. Bucks, on the other hand, may disperse 1-5 miles or more from their natal home range before establishing a new home range.

Third, you must consider that some bucks stick fairly close to home while others travel quite far — perhaps 5-10 miles or more — from their home range to breed. Given the possibility that any adult buck could potentially breed any adult doe while on his excursion, every deer within that geographic area could collectively be considered part of a “herd,” a term for which there is really no strict definition.

Now consider that home ranges can overlap infinitely. Unless there is a wide geographic gap in between where no deer exist, there’s no way of determining where one herd ends and another begins. Next consider the dispersal over time.

Now factor in things like hunting pressure, habitat, disease and predation, all of which can significantly influence deer densities. Where I live in southern Maine, we have about 10-15 deer per square mile. There are places in the Southeast and Midwest that might have double or triple those densities and, thus, could have at least three times as many deer in a “herd.”

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