By Alan Clark - Wildlife Section Chief of Wildlife Review Magazine
Published in Utah DWR Magazine -- Wildlife Review: http://wildlife.utah.gov
I've been a wildlife biologist for more than 30 years, and now my daughter is studying to be one too. She often asks me questions about why we hunt certain species the way we do. I'm frequently asked the same questions when I meet with people at events around the state of Utah or when I speak to a wildlife class at a university.
The interactions have helped me realize that people who are not directly involved in managing wildlife have many questions and assumptions about why we manage wildlife the way we do. I thought it would be interesting to address a few of these questions in this issue of Wildlife Review.
Why do we have separate hunts for buck and antlerless deer?
Management recommendations for Utah's mule deer are directly by the objectives in the Mule Deer Management Plan. The plan sets a population (quantity) objective for a total of 412,000 deer statewide by 2011. The plan also outlines a buck-to-doe ratio (quality) objective that guides the number of bucks (males) versus does (females, or antlerless deer). In most areas of the state, we're managing the herds so the ratio of bucks per 100 does is a minimum of 15 bucks per 100 does when the hunting seasons end in the fall.
To achieve those objectives, there are two types of deer hunts each year. The Utah Wildlife Board, with recommendations from division biologists, sets the number of permits for each of these hunts each year.
The buck-hunting season helps achieve the desired buck-to-doe ratio, while the anterless hunt moves the deer herds toward the total population objective. The reason two hunts are needed is tied to deer biology.
Bucks typically make up less than 15 percent of the total population. Since only five bucks per 100 does are needed to successfully breed all of the 100 does, the number of bucks in the population has little effect on the number of fawns born the next year. Even if half of the bucks in a population were harvested, for example, the total population would only be reduced by 5 to 10 percent.
So even when a total deer population is below objective, and we want that population to grow, we can continue to provide hunting opportunity for the "surplus" bucks in the population with little effect on the growth of the deer herd. For this reason, the buck-hunting season helps us adjust the buck-to-doe ratio, but does not have a major impact on the total population.
The anterless hunt produces a different result. When a doe is taken, both doe and the fawns she would have had in the future are removed for the population, which is a much bigger effect on the total population. For this reason, antlerless hunts are designed to get the total population to our objective.
Why is the ratio of males to females in an elk population so important?
Elk populations are also managed with quantity and quality objectives, but maintaining the proper ratio of males to females is even more critical because of the unique characteristics of elk.
Since elk are larger and consume more forage than deer, habitats can't support as many elk as they can support deer. Therefore, elk population objectives tend to be much lower than they are for deer. Also, on many management units we want bull elk to grow much older than buck deer because hunters prefer more mature bull elk. Meeting the lower population objectives, and keeping the harvest of bull elk at a level that's low enough to help bulls reach a mature age, can easily result in a large proportion of bulls in the population.
For this reason, a large number of antlerless animals must be harvested to meet our population objective, and that means mostly cows will be taken.
Taking cows has two effects. First, we end up with fewer cows in the population, and that means fewer calves will be born. Also, because we end up with a lot of bulls, more older bulls will be of lower quality and more of the bulls will have antlers that are damaged from fighting with other bulls. Hunters with a coveted limited entry permit don't want to take either of these types of bulls.
In many of Utah's limited entry elk units, the bull-to-cow ratios range from 50 to 80 bulls per 100 cows and sometimes even higher. Here's simplified example of how this happens:
If we have an elk unit with a population objective of 1,000 elk and an age objective of bulls that average 5 years of age, only three or four bulls per 100 elk can be harvested each year to maintain the age objective. The elk herd, however, is producing 30 calves per 100 elk each year, 15 of which are bull and almost all of which will survive.
At the end of one year, the elk population of 1,000 animals will have grown to 1,260 (1,000 starting population, plus 300 calves produced, minus 40 bulls harvested). To get back to the population objective, 260 elk need to be harvested, and most of them will be cows. If this is done for a number of years, the elk herd will shift more and more to bulls. There will be fewer cows in the population and fewer calves will be born.
Eventually, we will have too few cows left to produce enough calves to maintain the population. When that happens, we'll need to restart the elk herd by harvesting a lot of bulls and replacing them with cows. Without some additional management, we will have a population with little stability and with population numbers that fluctuate greatly.
A good solution to this is spike-bull (yearling male) hunting, which is used on the larger management units in the state and may soon be added to some of the smaller limited entry units.
The benefit of spike-bull hunting is that bulls are removed that would have grown to an older age. On spike-bull units, hunters can only harvest a bull with a spike antler on at least one side. Most of these bulls are yearlings, but even with a high harvest, 15 percent of the spikes survive. Also, some yearlings already have two points and are not legal to harvest during the spike hunt. The remaining bulls are then protected until they reach the quality hunters want to harvest.
Spike-bull hunts allow us to harvest three or four mature bulls per 100 elk in the population and still maintain our quality objective. We still hold antlerless hunts to meet population objective, but since we removed part of the population as surplus bulls, the harvest of cows is much lower and we can maintain a productive herd. This is the same idea as thinning your carrots when they're young so more of the remaining carrots can grow to the size you want to harvest.
Some call this management tool "catch-and-release elk hunting" since the spike-bull hunters have the pleasure of seeing the big bulls during their hunt but cannot take them home.
Why are we hunting so many buck pronghorn on Utah's Parker Mountain?
The Parker Mountain antelope herd is a good example of what happens when we let a big game population get above the population objective and have to play catch-up to bring it back.
Because of high-quality habitat on the unit, even during the recent drought the Parker Mountain antelope herd was extremely productive. While many antelope herds dropped to fewer than 10 fawns per 100 does during the drought, the Parker Mountain herd continued to produce 50 to 60 fawns per 100 does.
The antelope herd grew to an estimated 3,500 animals when our objective was 1,500.
How do we manage this herd to get us back to the objective? We chose to use surplus doe antelope from the unit to restock other units that had low populations because of the drought and to trade with other states for big game animals that Utah needed. When we transplant animals to supplement an existing herd or start a new one, we focus mostly on catching does that will produce fawns.
Capturing antelope is expensive, and only a few males are needed in a population, so over the past two years we've removed mostly females and fawns for transplant. Doing so has moved the herd closer to the population objective, but it also has left us with a high ratio of bucks to does. We've issued large numbers of buck tags to bring the herd closer to its population objective, but more importantly, to balance the ratio of males to females to provide a herd that's lower in number but more productive. After several years of expensive counts and intensive hunting and management, the herd will be brought back to its objective.
Why do we hunt turkeys in the spring?
Game bird species, such as grouse, quail, waterfowl and pheasants, have characteristics that are different from big game. With species that pair to produce and raise offspring, saving females at the expense of males would not gain anything since an equal number of both males and females are needed. Also, many species of game birds cannot easily be distinguished by sex (chukars and grouse, for example).
But turkeys provide and interesting example where, in conjunction with surplus males, behavioral differences between males and females are used to provide a unique opportunity for hunters.
Unlike many other game bird species, male turkeys gather a harem and breed many females, so there are surplus males in the population. The male turkey's behavior of displaying and gobbling makes it easy for even novice hunters to distinguish males, even though their plumage is similar to females'. Even after the hens are bred, the tom turkey will continue to display its unique behavior in the spring. Because of this behavior, we can provide spring turkey hunting with little effect on population growth, including the growth of populations that recently have been introduced to an area.
Fall hunts will be implemented in Utah once we reach our population objectives and want to control total population numbers.
I hope this article has helped take some of the mystery out of wildlife management. If you already have a good understanding of how wildlife populations are managed, you know that I have simplified the process. But I hope I've helped the novices understand the basic principles. If you think the article would form a good beginning to a series exploring other fish and wildlife management principles, please let us know.
Click-a-Pic ... Details & Bigger Photos
Click-a-Pic ... Details & Bigger Photos