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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

As a doe approaches estrus, a buck has a special way of drawing in the scent through the roof of its mouth. This special sniffing behavior, known as the flehmen behavior, enhances a buck's ability to detect the chemical messages in a doe's urine. © F. Eugene Hester

October 2004

Bucks in the rut

Remarkable photos catch whitetails in this season of signaling their mating intentions.

F. Eugene Hester


As a doe approaches estrus, a buck has a special way of drawing in the scent through the roof of its mouth. This special sniffing behavior, known as the flehmen behavior, enhances a buck's ability to detect the chemical messages in a doe's urine.
© F. Eugene Hester
Rubbing bushes and trees | Making a scrape
Twig licking | Scenting the scrape
Fighting | Sniffing air for scent
The chase

In autumn, a white-tailed buck makes a dramatic transformation. During the summer while his antlers grow, he socializes as part of a bachelor group. But as days shorten in early September, major changes take place. Testosterone levels increase, his antlers harden and the velvet supplying blood to his antlers dries to a ragged sheath that falls off. He rubs off the remains, polishing his rack like a barber stropping a razor.

From that time on he is a loner, focused on the mating season and using his keen senses to detect danger, rivals and receptive does. If he proves to be dominant, he can breed many does; the strongest and fittest bucks sire the most offspring.

A buck advertises his presence through numerous sensory signals leaving physical scrapes and signs. He applies scents from various parts of his body signaling other deer of his presence and dominance. Saliva, urine, pre-orbital glands in front of his eyes, forehead glands at the base of his antlers and tarsal glands on the insides of his hind legs all send aromatic messages to other deer.

Though scents may tell a lot about his readiness for breeding, the ultimate test of his dominance is the buck fight. Early in the season, young bucks and even mature ones may engage in skirmishes, but when breeding time is imminent, mature bucks may challenge each other in serious combat. With antlers pushed together, they shove and twist with tremendous force. The battle lasts from a few seconds to several minutes, until one of them admits defeat and leaves. The dominant buck focuses on finding receptive does and will fight other bucks along the way in his pursuit. Look for these signs and behaviors on fall hikes or while you scout out hunting sites.

Rubbing bushes and trees

Bucks start rubbing soon after their antlers complete their growth and harden. The initial rubbing removes the velvet covering of dried blood vessels that nourished the antlers during growth. Antler rubbing continues throughout the autumn months and intensifies as breeding time approaches. As the buck rubs bushes and trees, he leaves scent from forehead glands. Other deer detect both the physical appearance of the rub and the scent left behind. Additionally, rubbing may act like a mock shoving match as if shadowboxing with an adversary.

Making a scrape

A buck advertises his presence by pawing the ground and raking away leaves and grass leaving a bare ground spot two or three feet in diameter. Bucks scrape almost anywhere including the middle of a field or deep in the woods, but often they scrape along the edges between fields, pastures and wooded areas.

Twig licking

After making a scrape, a buck will often leave his scent in several ways. One way is to lick overhead twigs as high as the buck can reach without standing on his hind legs. Other bucks will smell and also lick the branch. It seems to provide a form of social communication.

Scenting the scrape

After making the scrape and licking the overhead branch, a buck often will urinate or defecate in the bared space leaving a lot of scent. He may also rub together the deeply stained tarsal glands located inside each hind leg and urinate on the tarsal glands, leaving a very strong odor of both urine and the scent glands in the scrape.

Fighting

During autumn, bucks continually look for opportunities to breed. Deer do not form pair bonds, but rather the larger and stronger bucks become dominant and breed many does. Bucks exert their dominance in many ways -- by their massive appearance, through stares and by challenging subordinates. At the peak of the breeding season, mature bucks do confront each other and a genuine fight ensues. With great speed and strength, bucks battle and antlers clash together as they vigorously push, shove and twist. The conflict continues until one admits defeat and retreats.

Sniffing air for scent

As a doe approaches estrus (heat), she provides behavioral and chemical clues that a buck will follow. She frequently stops and urinates advertising her state of estrus. The buck has a special way of drawing that scent into the roof of his mouth just inside his upper lip. This special sniffing action, known as a flehmen behavior, enhances his ability to detect the chemical messages she deposits in her urine.

The chase

When a doe nears estrus, the buck pursues her and they start running. He disregards all normal cautions likely exposing himself to the dangers of highways and hunters. He keeps other bucks away through threatening gestures, a grunt-snort-wheeze noise, or fights as necessary. When the doe is ready to conceive, she allows the buck to catch her. After breeding, the buck may stay near her for a day or two and breed again.

F. Eugene Hester has written and photographed wildlife and conservation stories for 50 years. Trained as both a wildlife and fisheries biologist, he had a distinguished conservation career in Washington, D.C. including service as acting director of the U.S. Fish and Wildlife Service, associate director of the National Park Service and acting director of the National Biological Service.