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Saturday, July 12, 2014

Surprising acorn abundance could reduce deer harvest this year

Friday, November 25, 2005

In an age when science has laid bare many of the mysteries of the universe, you would think biologists could predict a good acorn crop. You would be wrong. Missouri is in the midst of a superabundance of acorns, a fact that amazes experts.

Each year the Missouri Department of Conservation conducts a survey to determine the abundance or scarcity of acorns. This is important because a wide array of wildlife relies heavily on the fruit of oak trees for food. Acorn counts from thousands of trees give biologists valuable information about how ducks, squirrels, deer and turkeys will fare in the coming year.

The annual survey covers the portion of the state where forest dominates the landscape, roughly half the state lying southeast of a line from Hannibal to Joplin. The result is a series of acorn-production indices broken down by region and oak tree type -- red or white. Over the past 46 years, the overall index for all oak trees throughout the survey area has been 133. Last year, the number was 116. This year's overall index is 152.

Wildlife Management Biologist Dan Drees, who works in the Ozark Region, said this year's acorn crop beats anything he and others have ever seen.

"I have talked with loggers at Peck Ranch (Conservation Area) who have been working in that area 35 years, and they say they have never seen so many acorns," said Drees.

The news is similar throughout most of the survey area. The only exceptions are white oaks in the Ozark west and the Ozark Border at the western edge of the survey area. Even in those areas, the overall acorn crop was above average. In the eastern Ozarks, white oak acorn production is up 55 percent compared to the average of the last 46 years.

All this would be little more than scientific trivia except for one thing -- the firearms deer season. In autumn, deer gorge on high-energy foods in preparation for winter. In forested areas, this means acorns. When acorns are scarce, deer flock to trees that did produce acorns. This simplifies hunters' work. If they can find acorns, they will find deer.

Hunting is much tougher in years of acorn abundance. Deer don't have to travel far to find their favorite food, so they spend less time on the move, and they are scattered unpredictably throughout the forest.

Drees notes that this effect already is showing up in early deer harvest statistics. At Peck Ranch, bowhunters and participants in the two-day youth firearms deer season checked 105 deer last year. This year's total was 42. Hunters must check in and out during the hunts, so complete harvest reporting is guaranteed.

Resource Scientist Lonnie Hansen is the Conservation Department's deer management expert. He said he expects this year's deer harvest to be off on account of the superabundance of acorns.

"In the past, we have seen deer harvest decreases of up to 30 percent in some Ozark counties where there were bumper crops of acorns," said Hansen. With acorns so plentiful this year, the decrease in the Ozarks deer harvest could cause the statewide harvest to be significantly lower than last year.

The 2004 combined firearms and archery deer harvest was 309,893, a record for Missouri.

Drees is particularly surprised at the abundance of acorns because the state was gripped by a severe drought for much of the spring and summer.

"I have been shocked by this year's oak mast (acorn) crop," he said. "We had a horrific drought this spring at Peck Ranch. The period from March through June was the driest in more than 50 years. I would have predicted a total acorn failure. Yet, to my utter amazement, nature produced one of the largest acorn crops ever recorded."

Neither Drees nor other Conservation Department experts know all the factors that led to this year's acorn bounty. Resource Scientist David Gwaze, who assembles the Conservation Department's mast survey each year, said annual data point to some correlations between weather and acorn production. He said the number of red oak acorns seems to be higher two years after abundant spring rainfall, and white oaks are more productive in years with mild spring weather.

"So far we have not been able to find any discernable pattern that explains why we have good acorn production in some years but not others," said Drees. "We know some of the factors that play a role, but the combination is so complex, it is impossible to decipher."

Those factors include:

Late freezes: A cold snap can kill oak flowers, decimating a given year's acorn crop.

Wind: Oak trees need wind to carry pollen from male flowers to female ones. Unusually still weather can result in poor fertilization.

Rain and humidity: Wet weather also can impair pollination distribution. However, very dry weather, coupled with windy conditions also can hurt production by causing female flowers to dry up before pollination occurs.

Tree location: Trees on ridges may be less vulnerable to freezing and get better exposure to pollinating wind. As a result, acorns are most abundant on ridges in some years.

Drought: Too little rain during the growing season can impair a tree's ability to make acorns, even if flowers survive and pollination occurs. However, if this was ever going to make a difference, it should have this year.

"Those are just some of the factors we know about," said Drees. "A lot of other things probably influence acorn production, like conditions that favor the growth of beneficial or harmful fungi in the soil, tree diseases and parasites. The interaction of all those factors makes predicting acorn production practically impossible."

Rather than being dismayed by the complexity of the problem, Drees finds it reassuring that some things are beyond human understanding, let alone control.

"It is wonderful that we can put men on the moon and bring them back, but we still can't predict how many acorns there will be each year. Mother Nature doesn't give up her secrets easily."



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