Whitetail Deer Rut: Testosterone Poisoning of Bucks

Landowners and deer managers want to grow and produce big whitetail bucks—and hunters want to shoot them. If no one wanted to shoot them, then why would we put so much time and effort into deer management operations? The truth is that white-tailed deer represent THE big game animal of the majority of US hunters. But big bucks are not just susceptible to hunters, they can also be affected, even killed, by testosterone poisoning. So what is testosterone poisoning in deer, you ask?



Whitetail bucks go through many changes on an annual basis. Bucks experience antler growth, then those same antlers fall off. Bucks live happily in harmony during the summer, but then they fight to the death in the fall. Most of the major events in a buck’s life occur because of a single hormone, testosterone. For the most part, testosterone simply makes bucks more aggressive.

Testosterone Poisoning in Whitetail Bucks Results from Rut

Under this assumption, you would guess that testosterone levels in whitetail bucks during the summer would be low—and you’d be right. However, testosterone levels increase into the fall, causing bucks to rub the velvet from their antlers and fight with brush, trees and each other into the rut. A doe in estrous is all the more reason to fight for breeding rights. As most people know, aggression takes a lot of energy.

Bucks often fight for breeding rights for receptive does. Although the majority of these fights end quickly, or never begin at all due to offensive or defensive posturing, death can occur in deer. It also takes a lot of energy to chase does through the woods. In addition, just walking, trotting, and running and looking for potential mates takes a lot of energy. And let’s not forget that it’s often cold outside and nutrition is naturally stressed during this time. In short, the rut requires a huge amount of energy.

Much of this energy comes from a buck’s energy reserves, or stored fat. When that has been depleted, energy comes from the burning of muscle tissue. Keep in mind that a buck does not eat a whole lot during the rut, so it is important that the deer enter the breeding season in as healthy condition as possible. However, this is not always possible and testosterone poisoning can occur.

Bucks weakened by the additive effects of searching, fighting, cold weather and overall decreased body condition are prime candidates for injuries and secondary infections. To make maters worse, a high testosterone level restricts a buck’s immune system. This means whitetail bucks are susceptible to many more illnesses at time when their hormones are telling them to be more aggressive and less fearful.

Testosterone poisoning is not something that bucks directly die from, but rather something that can lead to mortality because of a culmination of events. This is especially true late into the fall and winter, during the period referred to as the post rut. Bucks that enter the rut in poor body condition or those that have poor nutrition following the rut (no recovery) are much more susceptible to testosterone poisoning. This is another good reason deer management practices such as habitat enhancement, winter food plots and supplemental protein feeding are a good idea on any property that is interested in maintaining a healthy white-tailed deer herd.

Leave a Reply

Your email address will not be published. Required fields are marked *