November 13, 2019

Yearling Buck Kills Alter State’s Deer Herd

“By shooting so many juvenile bucks, Wisconsin hunters prevent deer herds from producing well-balanced age structures and buck-to-doe ratios. Wisconsin’s 2013 buck kill was comprised of 61 percent 1.5-year-olds, 24 percent 2.5-year-olds, and 15 percent 3.5-year-olds and older. Maine was the only other state with an equally low percentage of older bucks. Yearlings made up 53 percent of its buck harvest.

The 2013 national average for the yearling buck percentage was 36 percent, with Arkansas leading the country at 8 percent. Other states with few yearlings in the statewide buck kill were Louisiana, 15 percent; Oklahoma, 20 percent; and Kansas, 21 percent.”<<<Read More>>>

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Is Maine’s Whitetail Deer Age Structure Changing?

*Editor’s Note* The graph and information below was crafted by contributor Richard Paradis from information provided by me in addition to his own information.

One of the most telling events that can occur in a deer herd is a change in age structure. In brief, age structure is a dynamic investigation into the complete breakdown of how many deer make up specific age categories. We are often discussing the relationship between male and female deer as well as the number of fawns (new born) in relation to the number of adult female deer. Seldom, or at least not to the same degree, is the age structure of a deer herd discussed.

A well educated and experienced biologist, providing they have been able to collect the necessary data, can tell what percentage of a deer herd makes up fawns; up to 1 and 1/2 years of age, young deer; 1 and 1/2 to 3 and 1/2 years old, and mature deer; over 3 and 1/2 years. The same biologist should know, according to the geographic information, as well as available habitat, etc. what the age structure of a herd should be in order to classify it as healthy and to make determinations as to what any harvest should be like for the upcoming hunting season based on herd structure and trends.

There can also be certain movements in that age structure that can indicate to the biologist that something is changing, alerting them to the need to investigate what those influences might be and make changes to the management strategies to maintain a viable and healthy herd.

Some people believe that in order to destroy a deer herd, something has to kill off all the deer, adults included. This is not entirely true. In theory, if there were never any new born deer to add to the herd and in combination with all other mortality to the deer herd, how long do you think it would be before the deer herd disappeared? Not long.

In this kind of scenario, an examination of the age structure might alert us to what could be happening. For the sake of discussion, let’s say a healthy deer herd looked something like this: fawn recruitment, that is the percentage of new born fawns that live to see their first winter, is 20% of the herd; Young deer, 1 and 1/2 – 3 and 1/2 years 50% and mature deer 30%.

In an attempt to keep this as simple as possible, let’s say that with the above situation of 20%, 50% and 30%, the average age of the deer is 2.9 years. If you played around with those percentages you would soon discover that it takes quite a dramatic change in those percentages to effect a noticeable move in the average deers’ age.

As an example, let’s say that in one year, the fawn recruitment was wiped out, i.e. 0%. That would increase the average age of the deer to approximately 3.3 years (I divided the 20% loss evenly between the remaining two age groups). Notice that what appears to be a rather small change in average age (less that 1/2 year), a complete loss of fawn recruitment is a devastating event. If we carried that out for a few years, where fawn recruitment remained at 0%, we can see that the age of the deer herd gets older and older. Once this is discovered, trust me, I think the deer herd is in trouble.

As far as Maine’s age structure for deer, I don’t have the kind of data necessary to calculate age structure and I’m not sure whether the Maine Department of Inland Fisheries and Wildlife(MDIFW) does either. I am assuming they must. What I did do is to extract some of the data that MDIFW provides in their deer harvest information to use to see if there can be determined any trends in age structure.

All that is available on the MDIFW website is harvest information beginning in 2005 through 2011. In each of these reports, MDIFW provides in their harvest data the percentage of take based on the same age classifications I have used above, i.e. fawn, young and mature. I pulled out of these reports those percentages and listed them by year. Mr. Paradis was kind enough to compile them into a graph for better visual comparison.

However, bear in mind a few things. The data extracted may not be a clear representation of the entire herd of Maine’s deer. This is harvest data only and there are restrictions to the sex and age of what deer can be taken and in what geographical regions. Therefore, the only way we can make good comparisons is with the ability to compare those items that remain constant.

In theory, if we had for these seven years the same number of “Any-Deer Permits” in all the same regions, this harvest data would be a bit more accurate and reliable for my purposes. However, the changes in the issuing of Any-Deer Permits did not change drastically statewide until 2009 when Any-Deer Permits were halted in Northern, Western and Downeast Maine and again for the 2011 deer hunting season. As such, I’m not sure exactly how to use harvest data for 2010 and 2011 in comparison with all previous years.

From the graphs and information below, you can clearly see the percentage of Young and Mature deer taken for each of the years listed, 2005-2011. Over the span of the seven years, the average percentage of Young deer harvested is 46.4% and for Mature deer, 20.4%.

Not really knowing how to handle the 2010, 2011 harvest data, one could conclude that there is a slight trend upward in the age structure according to harvest information. Is this something to be concerned about. I would think so. Is MDIFW keeping an eye on this data and any trends? I certainly hope so. If the age structure of Maine’s deer herd is on the increase, there has to be a reason, which is generally related directly to fawn recruitment. Without good fawn recruitment a deer herd is doomed. Depending upon the severity of that loss, will determine how quickly a herd becomes decimated.

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