by Brad Fitzpatrick

In the United States, whitetail deer, elk, moose and other mammals enter a phase commonly known as the “rut” during the fall of the year. This is the period when most of the breeding activity occurs, and most hunters know it is a great time to be in the woods. But what exactly is the rut, and what causes it to happen regularly each year?

One of the common misconceptions is that the rut is initiated by cold weather, but that hasn’t shown to be true. While weather can have an affect on animal movements, the rut is actually started by the length of days. As daylight hours shorten, the pineal gland in animals releases hormones that cause changes in the body’s biochemistry. Does and cows come into estrous, which means they are ready to breed, and bucks and bulls undergo similar chemical changes that causes them to become more aggressive and to mark territory with scent that tells females that they are in the area and warns other males to stay away. There is a lot of debate regarding the effect of moon phase on rut activity, and while some researchers believe it has little affect, others subscribe to the notion that moon phases actually can impact rutting activity, particularly around full moon phases. A consistent fact is that the timing of the rut coincides with the birth cycle so that females give birth in the spring.

The signs of the rut are unmistakable. Male deer rub their antlers on trees, scent mark the ground (commonly called scrapes) and become more active so they are more often seen during daylight hours. Science has also proven that female deer, elk, and moose don’t come into estrous just once. In fact, a study of whitetail does showed that they commonly come into estrous up to seven times if they aren’t bred. Likewise, it isn’t just the biggest and oldest bulls and bucks that breed females, so all age classes of deer are equally invested during this period.

The increase in deer movement is what draws most hunters to the woods during the rut, as male deer are more mobile and cover more ground in search of receptive females. For this reason, male deer may be on the move at just about any time of day, ditching their usual habit of moving primarily at dawn and dusk. All of this activity and movement causes a great deal of stress on these animals, and it’s not uncommon for bucks and bulls to lose up to twenty percent of their body weight during this period just prior to winter. That can cause significant strain on the animal’s body, and during the first part of winter when the rut is over, male deer have a significant need to find suitable food sources to help them survive the colder months.

Hunting in the rut means that your odds of seeing a bull elk, moose, or deer increase, but females are the key. A single buck or bull chasing a receptive female can create a situation where all the males in the vicinity are alerted and come to investigate, and this preoccupation with breeding offers hunters a great opportunity for success.