Elevated Testosterone: How it Fuels the Whitetail Rut, Part II

elevatedtFor more than five decades, I’ve been immersed in the whitetail’s world. Though I love photographing them every month of the year, nothing gets my whitetail juices flowing faster than thoughts of hunting or photographing during the rut. I find all aspects of their rutting behavior intriguing and energizing, and I feel blessed to have witnessed their world as I have.

Many things go into making whitetail behavior so fascinating. If I’ve learned one thing, it is this: Without the effects of hormones, autumn in the whitetail’s world would not be the same. Just as it takes gas to run a car, it takes testosterone to fuel a rutting buck.

Last week, we looked at various elements of the rut recipe. This week, we delve into the physical and behavioral changes triggered by elevated testosterone.

By Charles J. Alsheimer, Deer & Deer Hunting contributor

Physical and Behavioral Effects

Body: The first noticeable effect elevated testosterone has on bucks occurs soon after velvet peel, when the neck size of bucks begins to increase. This physical change is quite typical, especially for mature bucks, and I believe it’s a necessary process bucks go through to determine dominance.

Attitude: Increased levels of testosterone transform a buck from being docile from January through September to almost being a mad man by the time the rut explodes. When a buck’s testosterone valve is fully opened, no deer in his home range is safe. Therefore, few bucks come out of the rut without wounds. In some cases, they are so intoxicated with testosterone that their temper gets them killed.

Fighting: By mid-August, a buck’s testosterone level has increased to the point that the buck starts to show aggression toward other bucks in its bachelor group. From this point to velvet peel, stare-downs and threat-walking — precursors to fighting — are common. Twice, I’ve seen bucks aggressively fight antler to antler in full velvet during the week before velvet peel.

After velvet peel occurs, a buck’s attitude changes for the worse. Throughout September, much sparring occurs, and when October arrives, sparring matches can become quite ugly. From late October through early December, when testosterone levels are highest, fight-to-the-death encounters are common.

Activity: Testosterone levels greatly affect a buck’s activity level. To use a human example, testosterone does to bucks what amphetamines do to humans. During summer, when testosterone levels are low, bucks move very little, and it’s not uncommon for their home range to be less than 400 acres before mid-September. However, as soon as a buck’s testosterone valve is opened, a buck beds less and moves much more. Research has shown that by Oct. 1, a buck’s home range can be four to five times what it was in August.

When testosterone peaks in early November, a buck can easily cover more than 4,000 acres. When this happens, he encounters bucks he’s never seen before. As a result, fighting becomes the norm, and nothing good comes from these encounters.

Rubbing: When velvet peel occurs, there seems to be a lull in rubbing behavior, until about Oct. 1 in the North. From that point, rubbing intensifies before dropping off when breeding is finished. It’s well known that most of the rubbing done by bucks is for scent marking. However, I believe the most intense rubbing occurs because of the high level of testosterone in a buck’s system in October and November. When testosterone levels decrease, rubbing also drops off.

Scraping: Whitetails (bucks and does) will work overhanging licking branches 365 days a year to scent-mark their territories. It’s their way of communicating with all deer in their home range. Through the years, I’ve studied the whitetail’s scraping behavior extensively and observed that it doesn’t become intense until testosterone levels are near peak. In my area of New York state, scraping starts to explode about Oct. 15 each year before dropping off when the breeding period becomes full-blown.

A part of the scraping process is rub-urination. During the final step of making a scrape, a buck brings his tarsal glands together and urinates through them as he rubs them together. Though I’ve photographed this behavior every month, it doesn’t reach its peak until testosterone levels peak in early November in the North.

Doe etiquette: Without elevated testosterone levels, bucks pretty much leave does alone. With elevated testosterone, it’s, “Katy bar the door,” especially in the two-week period before peak breeding. During the two weeks leading up to breeding, bucks are relentless in their pursuit of does. Chasing can be intense, and if a buck corners a does in a blow-down or thick brush, the doe can be injured.

Breeding: As mentioned, testosterone and testicular volume in a buck and estrogen in a doe peak around the Nov. 1 in the North. This synchronization sets the stage for breeding to occur. Though testosterone drives the breeding process, high levels of the hormone are not required for a buck to breed a doe. Twice in my years of raising whitetails, I’ve seen antlerless bucks (they had shed their antlers in early February) attempt to breed does that cycled into estrus in March. Because of the bucks’ physical appearance, I knew their testosterone levels had bottomed out, but the smell of estrus still drove them to breed.

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