Deer Management 101

By V. Paul Reynolds

Interestingly, success rate for antlerless permit hunters is close to 30 percent. According to Gerry Lavigne, this higher success rate is due, in part, to the illegal practice of party hunting, and if hunters were to cease this illegal activity the state could double the number of antlerless permits they issue.

This is THE big month for hunting in Maine. The regular firearms season on deer, which began on October 30 for residents, will run until November 27 and more than 250,000 residents and non-residents will head afield after venison. Prior to that archers statewide had a month to try and collect their winter’s food. Archers hunting the expanded zone began in September and may continue until the culmination of deer seasons coinciding with the end of the muzzleloading season in December. Over the more than three months of deer season, hunters are expected to take nearly 30,000 deer.

Through it’s deer seasons, the state provides sportsmen with a tremendous array of recreational opportunities. But managing the state’s deer herd is no simple task. It takes a lot of careful research, modeling, planning, public input, and consideration of all the variables. To many it may seem like a black box; information goes in and seasons and bag limits come out. Still, the majority of hunters trust the management of this tremendous resource to our competent wildlife mangers. But there are always a few naysayers, usually those who didn’t get their doe permit, who don’t trust what “them biologists do anyway.” Whether you’re a skeptic, or just curious, here’s a general overview of some of the mystery that go into deer management.

Before you can attempt to manage deer, or any resource for that matter, you need to know what’s out there. The state has several ways of doing that. First, we have a long history of harvest records and hunting success rates – the number of deer taken per number of hunters afield. Success rates don’t change dramatically from year to year and the number of deer killed provides a good index of what’s actually out there. If success rates were to suddenly drop, that might indicate the deer herd is down.

State biologists also conduct winter surveys of deer yards. They go out into designated areas of winter deer concentrations and walk transects, counting the number of tracks, beds, and pellet groups they encounter. This information also provides an index of the deer population. It’s important to remember these indices show trends rather than actual numbers of deer.

Harvest data also provide a good index of the health of the deer herd. Each year biologists visit check stations and measure the antler beam diameter of a sample of yearling bucks taken. This measurement – yearling antler beam diameter (YABD) – is a reliable index of the health of individual deer in a particular area. Years of research have demonstrated a direct correlation between YABD and carrying capacity. Average YABDs of 15 – 16 millimeters or less generally indicate that the population is exceeding the carrying capacity. The 17 – 19 mm range generally indicates deer are near carrying capacity. When average YABD exceeds 20 mm, it’s a good indication that deer are below the carrying capacity and there is ample nutrition.

Now that we know roughly how many deer we have in each region, and how that numbers corresponds with available habitat, we can begin to set seasons and limits. This is where things start to get complicated.

First, we’ve determined only the biological carrying capacity – how many deer the land can support. Biologists must also consider the cultural carrying capacity – how many deer the human population will tolerate. This is especially important in the more populated areas of the state where, in some cases, deer are now exceeding those limits, as evidenced by the dramatic increase in car – deer collisions and property damage complaints. Thus, the expanded archery season.

Another important consideration to managers is how to maintain a sustained yield of deer. In other words, how do they ensure there will still be enough deer around after hunting season to sustain the population? Managers also need to know what type of a hunting experience and success rate the majority of deer hunters want. Do they want high success rates, which usually means a large proportion of the bucks killed are yearlings? Or would they prefer a slightly lower success rate, with a greater chance of taking a mature buck weighing in over 200 pounds and possibly sporting a trophy rack? The unfortunate truth is: you can’t have both. In general, Mainers have, thus far at least, been satisfied with the state managing for a quality deer herd rather than high kill rates.

You’d think that this would be a nearly insurmountable task. But thanks to volumes of research it’s really not all that difficult. That’s why our venerable deer biologist Gerry Lavigne is so often right on with his deer harvest predictions. What’s his secret? He hedges his bet by working with regional biologists to make recommendations for the number of antlerless permits allocated for each region. Then, by plugging anticipated success rates into an established framework of season lengths, predicting the outcome is easy.

The trick is to ensure consistent harvests from year to year. This is accomplished largely by setting the number of antlerless permits available. Deer are polygamous – one buck can mate with many does, who in turn give birth to fawns. So harvesting bucks has significantly less impact on the long term productivity of a deer herd than does harvesting does.

A simplified way to look at it is this. If you take one buck this year, that will be one less deer around next year, and the year after. But if you remove one adult doe from the population, that will be three less deer next year, and potentially nine fewer deer the next. That’s why we have a “bucks only law. If everyone could hunt for either sex we’d soon run out of deer.

Managers must also determine how best to partition the resource among the various user groups: archers, firearms hunters and muzzleloaders. Prior to the expanded archery season, archers and muzzleloaders combined for less than 10 percent of the total annual harvest. However, the firearms hunters are an important entity. This was taken into consideration, which is why the expanded archery zone is restricted to “locations where deer populations can withstand additional hunting pressure without negatively impacting existing deer hunting opportunities or human safety.” Archers may harvest a larger proportion this year, but most of those deer would be otherwise unavailable to rifle, shotgun, and muzzleloader hunters. By shortening the gun season, the state could potentially increase the bag limit, but Mainers hold dear their long firearms season.

The next step involves determining how many antlerless deer permits to make available, one of the most contentious issues in deer management. This number is based on the deer population in each region and anticipated success rates. Interestingly, success rate for antlerless permit hunters is close to 30 percent. According to Gerry Lavigne, this higher success rate is due, in part, to the illegal practice of party hunting, and if hunters were to cease this illegal activity the state could double the number of antlerless permits they issue.

So there you have it – a very simplified view of how and why we have the seasons and limits we do. Mainers should be proud of their deer resource, and the professionals who manage it. We have one of the longer regular firearms in the country, yet still boast one of the highest ratios of mature bucks in our harvest, while still maintaining an average success rate within the national average. In addition, we now have an archery season that allows multiple deer. All things considered, its an enviable situation.

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