Why Don't They Gobble?
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The thunderous gobble of a trophy tom is a sound of spring that can raise a hunter's blood pressure. It gets the adrenaline pumping. While it can be frustrating to have a gobbler seem so close, but hidden in the pre-dawn darkness, it is more frustrating to be met by the silence of the morning air when you know there are turkeys in the area. Every hunter is challenged at some point during the season with the question of: Why aren't the turkeys gobbling?
From changing barometric pressure to too many hunters in the woods, numerous theories exist to explain a sudden reduction or lack of gobbling. The only theory that seemed to have some credence was that turkeys learned to associate gobbling with unwanted attention from hunters in the form of disturbance, hunting pressure and gunfire.
To test this hypothesis, biologist Chad Lehman designed a study on Merriam's wild turkeys to determine if gobbling activity is affected by hunting pressure. The design of the study also allowed researchers to determine if weather and nesting activity affected gobbling activity of Merriam's wild turkeys.
The study took place in South Dakota, within Wind Cave National Park (non-hunted population) and the adjacent Black Hills National Forest (hunted population).
The only major difference between the two study areas is that the Black Hills allows hunting during the spring turkey season. Since the properties were adjacent to each other, any environmental factors such as rain, incoming weather fronts or temperature would affect both populations equally and would be easily detected.
Researchers listened to birds at the exact same start times in both study areas during the early mornings. Researchers counted the number of gobbles while they were on roost, starting 40 minutes before sunrise, and continued their counts 65 minutes after sunrise, when the majority of birds were off the roost. In addition to listening to gobbles along transects, some gobblers were radiomarked along the gobbling transects to collect movements in relation to hunting pressure and roost fly-down times.
"We observed two peaks in gobbling activity during the spring," said Lehman. "The first followed the winter break-up of flocks, which usually happens just before turkey season opens; and the other just before or during peak incubation, which is during the regular turkey season."
When the field staff was correlating gobbling activity to environmental factors, such as precipitation, barometric pressure and the timing of nesting, there were no relationships that predicted gobbling activity. However, the results comparing hunted and non-hunted birds proved to be much more interesting.
"When we tallied the average number of gobbles per bird, we found that before the hunting season opened there weren't any differences between the non-hunted and hunted populations," said Lehman. "However, when the turkey hunting season was in session, the non-hunted birds gobbled significantly more times than the birds in the area that allowed hunting. Even more interesting is that after the season closed, the average number of gobbles for the non-hunted birds and hunted birds returned to significantly similar numbers."
Lehman's study seemed to validate what hunters have anecdotally observed in the field for many years — hunting pressure does affect the frequency of gobbling.
"During the study we observed hunters applying pressure on several occasions, typically by approaching, setting up and aggressively calling at gobbling males either on the roost or while males were courting females at strutting areas," said Lehman.
The study suggests that the hunted birds negatively associate gobbling with seeing other turkeys being shot or learning that not all calling is coming from hens, but from hunters nearby.
— James Earl Kennamer, Ph.D., NWTF Chief Conservation Officer