By the Light Of the Moon

The pull of the moon is powerful, and so are its effects on the natural world. Some deer hunters plan their season around the stages of the lunar cycle, convinced that whitetail activity, including the rut, is highest during specific moon phases. Some hunters are convinced they see more deer during the day after exceptionally dark nights as the result of a new moon. Those dark nights make it tough for deer to see, the theory goes, forcing them to move more during daylight hours. Others are certain the primary rut takes place during or close to the second full moon after the autumn equinox. It's often called the rutting moon.

Many dedicated hunters are convinced that lunar phases are critical for timing deer movement and that wildlife is more active during specific moon phases, but plenty of evidence suggests otherwise. Researchers from the University of Georgia's D.B. Warnell School of Forest Resources wanted to figure out if lunar phases affect the timing of deer breeding behavior. In other words, should deer hunters looking for the buck of a lifetime focus their efforts on a full, new or partial moon--or does any of that make any difference at all?

David Osborn, Dr. Karl Miller and Dr. Robert Warren, UGA wildlife research biologists, used breeding date data from various state wildlife agencies to determine if moon phases had any effect on whitetail doe estrous cycles and thus the rutting activities of bucks.

In the 2000 study, breeding dates were gathered from more than 100 captive deer in four states and more than 2,500 free-ranging does in seven others. The information was gathered over a period of three to 19 years, depending on the state, and then compared to lunar cycles throughout the birth date ranges.

"We would expect annual breeding dates for a population to be similar if calendar date [and therefore the same length of daylight] was the driving influence," explains Osborn. "We would expect annual breeding to be less similar if moon phase is the driving influence because a particular moon phase might vary as much as 28 days across years."

Scientists have long concurred that photoperiod--the length of daylight--has more influence on whitetail breeding activity than any other factor, despite what some hunters insist. Osborn says the evidence is quite clear: The phase of the moon has virtually nothing to do with the timing of whitetail breeding activity.

In fact, state wildlife biologists all over the country readily and confidently use calendar dates to help hunters plan their outings to coincide with the peak rut activities. Virginia lists November 15 as the peak of the rut, Nebraska hunters should head for the river bottoms sometime around the first of October, and Minnesota hunters need to be in their deer stands the first week of November.

But while these dates are good guidelines, they're not the final word on rutting activity. "It's really impossible to choose a specific date because of a variety of outside factors," says Virginia's deer project leader Matt Knox. "I'd say that November 15 is a pretty consistent date for the peak, but it's going to vary a few days on either side."