New research reinforces what many of us have long realized: wolves have a big impact on elk behavior, survival and even antler size.
Bull elk may need their antler adornments more than any member of the deer family, due primarily to the animal’s close association with wolves. Elk are the favored prey of wolves and their Goldilocks-like preference for perfection. Deer are on the small side for a full pack, and oversize moose, while satiating, increase the risk of injury.
Elk are just right.
Bulls need antlers to survive and are so reliant on them to fend off wolves they retain their antlers months longer than other members of the deer family. Moose lose their antlers soon after the breeding season. Whitetail and mule deer keep their antlers longer, but not as long as elk.
Those species deal with the threat of wolves differently. Moose rely more on size and strength; deer counter wolves with speed. The trade off is that by losing ungainly antlers sooner, and not carrying around extra weight, these species instead add weight where it counts: fat reserves.
Bull elk stand and fight when attacked by wolves, and unantlered bulls are up to 10 times more likely to be attacked, according to the paper authored by Matthew Metz, a Ph.D. candidate at the University of Montana. Metz conducted his research in the great elk/wolf lab experiment that is Yellowstone National Park.
The primary purpose of antlers is somewhat like that of a ’76 Corvette. Boy elk use them in order to woo girls. The most dominant bulls gather females into harems in the fall, when these antlers also come in handy fighting off competing bulls. The mating season, or rut, ends in the fall. For the rest of winter, elk repurpose their antlers as defensive weapons.
Elk in the park drop their antlers at roughly, but not exactly, the same time. The older, most mature males, drop their antlers in early March. This gives them a few weeks head start regrowing a new set for fall.
In the case of elk antlers and female-wooing success rates, size really does matter. In Yellowstone’s wolfless era last century, early adopters of the antlerless lifestyle gained all the advantages, with none of the risk. Since we restored wolves to that ecosystem, however, things have changed. Early March is still winter in Yellowstone, a time when deep snow and scarce food weakens elk, leaving them especially vulnerable to coursing predators like wolves.
Elk don’t consciously choose when to shed their antlers, but there’s always some variation built into any species. Pacific salmon, for instance, are hardwired to swim upstream to their natal spawning grounds in river headwaters, where they repeat the act of creation. Still, there are a few fish, no doubt compelled by wanderlust, that do things differently. In some cases they miss their native watershed entirely, and in unknown territory, likely aren’t as successful finding the right place to spawn.
So what’s the point of such seemingly futile behavior? Catastrophic events such as fire sometimes wipe out entire watersheds. Once these fishless watersheds recover, it takes wandering salmon to repopulate them.
There’s often tension in nature. For bull elk there is tension to get as early a head start on the upcoming breeding season as possible. Eliminating wolves gave early-bird bulls in Yellowstone a competitive advantage, and it’s likely elk in the park are still adjusting to this new reality. In 50 years, the biggest bulls in the park may not cast their antlers until late March.
This interspecies relationship is a sometimes brutal dance, a dance that has continued since wolves and elk first encountered one another in the Pleistocene, shaping the behavior of one another ever since.
You really can’t have one without the other.