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Elk: The Rut

The following information covers the biology of the pre-rut thru to the winter season for the Rocky Mountain Elk.

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Late June: It begins with the summer solstice. For elk, the daily decrease in daylight hours –as metered by the eyes and registered by the hypothalamus, which in turn is regulated by the pituitary – forecasts the hormone production that initiates and directs the rut. Most notably, in bulls, the testes begin to swell, fueling up for the action soon to come.

Early August: Among Rocky Mountain elk, visible rutting activity begins now, just before velvet shedding. Until now, bulls have been social and relatively at peace, with aggressive behavior limited to the head-up hissing display. If there is a dispute, generally it is settled by striking with the front legs, since velvet antlers are delicate and sensitive.

The neck mane has not yet started to grow; that must await the hormonal changes triggered by velvet shedding and will not be completed until sometime in November. Consequently, the Rocky Mountain bull elk ruts with a short mane.

Mid- to late August: With remarkable synchronicity, bulls now shed their velvet and become aggressive. Sparring begins immediately after shedding, and the first bugles sound. With the last days of August, bulls begin dispersing to their respective rutting grounds – places they’re familiar and comfortable with from previous ruts, and where cows are known to congregate.

Early September: With the onset of bugling, bulls begin perfuming themselves with pheromones by self-urinating and wallowing. A related ritual, commonly called horning, involves thrashing brush and young trees with antlers. Horning generally occurs during vocal or visual interaction with rival bulls, and serves to signal confidence and the intent to dominate. Preferred rub trees are conifer saplings two to four inches in diameter and seven to ten feet tall, from which bark is scraped, branches are stripped and the trunks are occasionally broken. Dominant bulls also horn trees as part of the self-marking ceremony prior to wallowing; often, dark neck hair can be found on these mutilated victims of the early rut.

Bull wallowing entails digging-out dry “scrapes”, or, more often, churning mud or shallow water into a froth, urinating on belly, under-neck and ground, and then rolling in the resulting muck. The object is to coat the neck mane with pheromone-laden urine and wallow mud, which is then transferred to nearby “billboard” trees or other vegetation by neck rubbing. Also during September, bugling increases and herding and courting behavior begin in earnest.

Mid-September: By now, dominant bulls are gathering and guarding breeding herds, all the while being harassed by off-prime, or “satellite” bulls, old as well as young.

To maintain his herd, a harem-master must distinguish himself, through both advertising (bugling, bluffing, horning, ritualized antler displays) and valor, so that cows will cling to him as an island of peace, where less competent and therefore less desirable bulls don’t dare venture. Even so, this is still the pre-rut, which technically continues until breeding begins, any day now. Now through early October, cows will come serially into estrus and seek to be bred by dominant bulls. Lesser bulls continue to be a bother to both cows and herd- masters, even as the physical condition of active herd bulls gradually deteriorates.

Late September: While reliable data are scarce, wallowing should peak in late September and continue, gradually decreasing, through late October. By then, some exhausted herd-masters may actually leave their harems in order to rest, abandoning unbred cows to younger males.

Early October: As fewer and fewer cows remain to be bred, bugling decreases.

Late October: By now, with rare exceptions, the rut is finished for another year. Cows regroup in winter herds, including calves and yearling bulls driven out during the rut. Bulls fall silent and become increasingly solitary, resting and feeding in an attempt to recover from rut exhaustion and battle wounds before the onset of winter. Many do not succeed, accounting for the high winterkill rate among prime males. Next comes moving to winter habitat.

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