Elk Bugle for Survival During Autumn

Photo by Jeff Vanuga

Mid-August or so, elk (Cervus elaphus) in Yellowstone National Park enter their breeding season, or rut, and the meadows and forests of the Greater Yellowstone Ecosystem are filled with the haunting bugle of the bull elk.

If you’ve never heard it before, an elk bugle does sound kind of weird – an odd combination of noises in sequence, from a low bellow rapidly rising up to a high, screeching whistle, followed by a series of grunts. This cacophony of noise is music to the ears of elk cows, who gather into harems of 20-30 females.
The bull elk is way too busy, and focused on passing on his genes to future generations, to worry about little things like food and sleep. For the sake of genetic survival, the mature bull elk is constantly on the go – a 700-pound to half-ton Energizer Bunny with antlers and an urgent desire to impregnate his females.

While human males have been blessed (or cursed) with instincts and hormones for year-round romance, the bull elk peaks for about a month or two each year – a go-for-broke evolutionary strategy. It is as if the hormonal spigot was suddenly turned from off to wide open.

The bugle of the bull elk serves several purposes, according to biologists, including:
–Attracting more cows for his harem;
–Intimidating young bulls who aren’t quite ready for prime time; and
–Announcing to young rivals that they’re invited to take his harem, if they dare.

And young bulls do take up the dare – stepping into a meadow with a challenging bugle, followed by a clash of antlers.

These explosive shoving matches with antlers put human sumo wrestlers to shame. Grass and shrubs are torn up in the scrimmage. Small trees in the area may already be torn and tattered, after bull elks charge them with their antlers in mock battle.

Bull elk confrontations can turn bloody as antler tines stab and rip muscle and sinew. Indeed, the average mature bull elk can sustain several wounds during a rutting season. Quite aside from the risk of dying in battle, a bull elk pays dearly for these wounds of honor, investing energy into healing that might otherwise be available for surviving a cold winter.

Bulls have been known to die during the rutting season, most often when antlers lock up against each other. Their owners are locked in a deadly embrace, to die of hunger, thirst and exhaustion.

More often they break away and the challenger leaves in hopes of better luck on another day, against another dominant bull. Yet all old bulls eventually lose to younger ones, leaving the once-dominant bulls to fade away into the forest and eventual confrontation with a wolf pack or a brutally cold blizzard.

There are other strategies for passing on genes into future generations – the first is the sneaky one.

While a dominate bull battles with an feisty challenger, a younger bull can sneak into the harem, hustle a cow, mate and be gone before the dust settles between the other two bulls.

Another strategy is more controversial. Canadian researcher Valerius Geist, interviewed in “Bugle, The Journal of the North American Elk Foundation,” has a theory about “shirker bulls,” who initially avoid rut season competition for several years. While competitors are beating up on each other, the shirker bull expends all his energies on growing bigger, said Geist. His theory is that the truly exceptional, world-class trophy antlers are produced by shirker bulls.

He’s seen a real life example of his theory in observations of a mule deer buck in Waterton National Park. A four-year-old buck was soundly thrashed in his first rutting season and stayed out of the fray for several years thereafter, said Geist. The buck grew bigger antlers than his competitors and after a harsh winter caused a large die-off, the now huge buck found himself with no competition and all the does to himself, Geist added.