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Vail Daily column: Be aware for signs of rutting season

As the air becomes cool and crisp and the mountains transition from shades of green to a collage of fall colors, keep your eyes open for the unique silhouette of the Shiras moose as they finish up the rutting (mating) season. While these handsome creatures are seldom spotted in the Eagle Valley, the moose population has increased in the last 30 years. Until the late 1970s, the only moose in Colorado were the few transient wanderers, heading south from Wyoming to find new habitats. If given enough time, then these moose may have established their own populations here in Colorado, but between 1978 and 1987, wildlife biologists decided to speed up the process by arranging several small-scale moose transplants from populations in Utah and Wyoming. The early moose in Colorado prospered and, soon after introduction to Colorado, the population was expanding to new areas of the state. Since then, our moose population has grown exponentially, reaching close to 1,000 individuals today — an overwhelming success for the moose! Although there is no guarantee you will see a moose as you walk around the valley, now is the time to start looking, as the normally solitary moose enter the annual rut and become very social creatures.

Colorado’s Shiras



While all of the moose across the world belong to one species, alces alces, there are several subspecies across North America. Here in Colorado, we see the Shiras moose (alces alces shirasi), which have the smallest body size and antlers, weighing in at about 800 to 1,200 pounds and standing up to 6 feet tall at shoulder height — nothing to be ashamed of, Shiras! They are typically dark brown in color, with a long head, a hump between the shoulders, long legs, and a funny flap of skin, sometimes called the “bell,” hanging from their throat.

For most of the year, moose live solitary lives, feeding, sleeping and slowly moving from one place to the next. During the summer, they may spend up to 13 hours a day grazing in order to gain weight for the cold winter, grow a new coat, and for bulls, a large pair of antlers. By early September, the velvet on their antlers is shed, 250 pounds of fat has been gained, and the bulls are beginning to move to new locations to seek out cows and begin the rut.



Sparing Stage

The first stage of the rut is known as “sparring:” a pre-fight ritual to prepare for the real fighting later in the season. The bulls will dig a pit in the dirt, urinate in it, and splash the urine-mud blend on their neck and antlers to create an attractive perfume. The scent grabs the attention of female moose and actually coordinates the fertility of the cows. Both female and male moose will become very vocal during this period, with males emitting low grunts and females producing wailing moans that can be heard up to a mile away. By mid-September, the cows begin forming groups, which may contain up to 25 female moose. When the bulls come across a group of cows, they compete with other males for breeding rights. Unlike the sparring, bulls engage in violent fights that may last for hours and can end in fatal injuries. The stronger, more experienced bull will win the fight, along with the right to breed with a group of females. Mating occurs in late September and early October — right about now!



Be Careful

So as you enjoy the fall weather, continue to pay close attention to your environment. You may be lucky enough to hear the deep vocalizations of the rutting moose, experience a private showing of the aggressive bull fights or simply catch a whiff of their musty urine perfume in the passing breeze. If you do come across one of these incredible creatures, then remember that they are wild animals and in a sensitive stage of their life cycle. They are likely to be more aggressive during this time, so try to avoid creating disturbances and observe from a safe distance. Happy rutting season!

Johanna Gundlach is a naturalist at Walking Mountains Science Center in Avon. From New Orleans, Johanna enjoys breathing in the dry mountain air and living more than 0.6 meters above sea level.


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