A surge of testosterone: One buck’s story

Everyone knows testosterone often rules the male psyche. So how does this vital hormone — and the mates they pursue — affect bucks during the rut?

The rut is on. Mature bucks, if not pursuing does, are tending and breeding estrous females.

The playing field has many contenders; yet one particular buck is not only dominating a given area with two different doe groups, but his body size is exceedingly large — even to the point of abnormality.

As he tends a doe, his entire body from forehead to the hindquarters is swollen. It appears as though his body and neck have been stuffed with pillows.

Yet the most obvious and unusual feature is the buck’s face, which is round like a basketball. It’s even to the point that his eyes are sunken due to the facial muscles being enlarged.

His forehead is swollen — giving the impression he has intensely rubbed trees or has had grueling antler-clashing fights with rival bucks.

Also, the buck’s head, neck and body are so puffed up that his antlers are out of proportion and look small.

Is this buck diseased, or is an unusual hormonal function going on?

Sickness surely isn’t the case: He is fully alert to his surroundings and quick to run off all competing bucks. He intensely tends estrous females.

Despite his appearance of being slow and sluggish like an overweight hog, the buck is strong, swift and right on cue with rutting behaviors.

Breeder’s history

Through the years, this particular buck accurately identified and nicknamed “Breeder,” has been consistently observed dominating several woodlots with estrous females. He was estimated to be 6½ years in age.

Despite his decline from maturity, he was still a full-blown rutting stag.

Year after year, Breeder displayed the typical rutting pattern. Testosterone increased with normal neck swelling. In comparison to other bucks battling over the same rutting grounds, he was just another mature, dominant buck attempting to mate as many females as possible.

Just prior to the 2008 rut in September, Breeder was observed several times after velvet shed where he appeared perfectly normal. As November kicked in, Breeder still maintained a typical buck appearance and had gained more weight due to a good acorn crop, as did other bucks.

However, when the majority of does were in heat, Breeder changed significantly to an obese appearance. He vigorously tended a doe in heat — running off rival bucks. He bred the doe; and within just an hour, he caught wind of another estrus doe within very close proximity.

Breeder then tended and bred this particular female — most likely the daughter to the first doe bred.

Periodically he checked the receptively of the doe he initially mated. Simply, he was able to court two estrous females at the same time — a very rare and unusual sight for a rutting buck.

Typically, whitetail bucks are not known for having a harem group to mate — a behavior more common amongst elk.

A week later, as the majority of females came out of heat, Breeder’s swollen body and head returned to what a normal rutting buck looks like.

No other bucks in the vicinity, based on my observations, ever displayed such a bizarre appearance.

As the post-rut finally unfolded, Breeder showed some loss of body weight. Testosterone had diminished significantly, as well.

In years past, Breeder rutted the same as all other bucks, and had normal neck and throat enlargement. But during the height of the 2008 rut, he undoubtedly experienced an unusual shift in testosterone, giving him anything but the appearance of being normal.

So what caused this bizarre appearance, and why just this one buck during the time of peak estrus?

My first inclination was an explosion of testosterone.

A biological explanation

For an accurate assessment on Breeder, I consulted noted deer expert Karl V. Miller, who has been conducting extensive biological research on whitetails for years.

Although he has witnessed rutting bucks with swollen head and neck levels close to Breeders, he agrees that the level of neck swelling on this particular buck was exceptional.

Miller ruled out the possibility that Breeder had a hormonal imbalance with the pineal or pituitary glands (instrumental for hormone production), and attributed Breeder’s swelling to an elevated testosterone level.

I also inquired if another hormone could have contributed to his bizarre head and neck swelling, but Dr. Miller said that was unlikely.

“Testosterone and its physiological derivatives are the only hormones shown to be responsible for buck rutting behavior,” he explained.

Being that Breeder’s surge of testosterone was in perfect synchronization with the majority of females being in heat in this area and that he mated two different females in one day, Miller pointed to the does as a possible trigger.

“There is some type of feedback mechanism between buck and does to ensure they are both in peak breeding condition at the same time,” he said.

He also said he believes that when bucks investigate doe urine using the vomeronasal organ through lip curling (flemen), the vomeronasal stimulates the hypothalamus — located in the brain and linked to the pituitary and hormone production.

In turn, the males’ testicles are triggered, thus producing increased amounts of testosterone.

When does are signaling breeding receptivity, bucks are instinctively excited — throwing them into a frenzy of rutting madness. Theoretically, with so many female signals being given off through urine/vaginal secretions and body posturing, Breeder swelled with elevated testosterone.

Yet once the estrous does minimized and/or ceased all their attractants to mate, Breeder deflated and returned to more of a normal appearance for a rutting buck.

In other words, he became instinctively aroused with an abundance of estrous does, which in turn caused his testosterone to explode beyond normal levels.

Doe-in-estrus lure

So here was an unusual case of elevated testosterone with a rutting buck. Not only was his appearance and the fact that he dominated and controlled the breeding for a small number of does unusual, but the situation confirms the time and placement of scent lures.

For years, hunters have periodically used doe-in-estrus products to attract bucks — especially during the height of the rut.

However, it is difficult to compete with the real thing. By all means, according to scores of hunters, hunting over a bunch of receptive ladies is undoubtedly going to draw bucks.

But, bucks that can’t get in on the breeding action, even mature bucks in the vicinity are more likely to investigate a doe in estrus lure than dominant bucks locked up.

Along with years of hunters attesting to experiences afield and biological research, Breeder’s account validates that doe-in-estrus lures can be an excellent buck attractant — depending on the product, how, when and where it is utilized.

Some seasoned hunters carefully gather dirt and fresh estrus doe urine at scrape sites visited by females. Placing fresh estrous secretions in mock scrapes has proven to be an extremely effective enticement for rutting bucks.

A behavioral confirmation

Although Breeder is a free-ranging, un-hunted whitetail, through all the years he has possessed an extremely skittish disposition — keeping a distance that telephoto lenses couldn’t capture professionally. The only times for good successful photographic results have been when he tends a human-habituated female in heat.

Breeder’s behavioral shift before and during breeding confirms that some dominant mature bucks will let their defensive instincts relax somewhat when estrus is in the air.

Of course, if does are being harvested, most hunters stress that taking a buck will get even more difficult — simply because all deer are pressured.

Even so, that brief moment of time when a buck mates provides the chance to capitalize on its vulnerability, whether one is pursuing whitetails with gun, bow, or camera.

The instinct to procreate puts a stupor on the rutting buck.


Finally, another confirmation found in Breeder’s rutting history is that an undisturbed concentration of females is a magnet for rut-crazed bucks. If the majority of these females come into estrus on certain dates within close proximity of one another, then the mature dominant bucks aren’t going anywhere.

Most hunters know that the trick is to get into position and not disturb the action. A surge of whitetail testosterone and the created world will do the rest.

About Tommy Kirkland 24 Articles
Tommy Kirkland aggressively pursues whitetails with camera and extensive observational work on free-ranging deer. He is a novice turkey hunter; and his articles and photos have been featured in many outdoor publications.

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