Elk Information Continued
Elk are the most abundant large mammal found in Yellowstone. European American settlers used the word "elk" to describe the animal, which is the word used in Europe for moose (causing great confusion for European visitors). The Shawnee word "wapiti," which means "white deer" or "white-rumped deer," is another name for elk. The North American elk is considered the same species as the red deer of Europe.
Bull elk are one of the most photographed animals in Yellowstone, due to their huge antlers. Bull elk begin growing their first set of antlers when they are about one year old. Antler growth is triggered in spring by a combination of two factors: a depression of testosterone levels and lengthening daylight. The first result of this change is the casting or shedding of the previous year's "rack." Most bulls drop their antlers in March and April. New growth begins soon after.
Growing antlers are covered with a thick, fuzzy coating of skin commonly referred to as "velvet." Blood flowing in the skin deposits calcium that makes the antler. Usually around early August, further hormonal changes signal the end of antler growth, and the bull begins scraping the velvet off, polishing and sharpening the antlers in the process.
The antler growing period is shortest for yearling bulls (about 90 days) and longest for healthy, mature bulls (about 140 days). Roughly 70 percent of the antler growth takes place in the last half of the period, when the antlers of a mature bull will grow two-thirds of an inch each day. The antlers of a typical, healthy bull are 55–60 inches long, just under six feet wide, and weigh about 30 pounds per pair.
Bulls retain their antlers through the winter. When antlered, bulls usually settle disputes by wrestling with their antlers. When antlerless, they use their front hooves (as cows do), which is more likely to result in injury to one of the combatants. Because bulls spend the winter with other bulls or with gender-mixed herds, retaining antlers means fewer injuries sustained overall. Also, bulls with large antlers that are retained longer are at the top of elk social structure, allowing them preferential access to feeding sites.
Calves are born in May and June. They are brown with white spots and have little scent, providing them with good camouflage from predators. They can walk within an hour of birth, but they spend much of their first week to ten days bedded down between nursings. Soon thereafter they begin grazing with their mothers, and join a herd of other cows and calves. Up to two-thirds of each year's calves may be killed by predators. Elk calves are food for black and grizzly bears, wolves, coyotes, cougars, and golden eagles. Female elk can live 17–18 years. Rare individuals may live 22 years.
Climate is an important factor affecting the size and distribution of elk herds here. While nearly the entire park provides summer habitat for 10,000–20,000 elk, winter snowfalls force elk and other ungulates to leave most of the high elevation grasslands of the park. Less than 5,000 elk winter in the park. Elk on the northern range Yellowstone's largest elk herd winters along and north of the park's winter boundary. With more moderate temperatures and less snowfall than the park interior, this area can support large numbers of wintering elk. The herd winters in the area of the Lamar and Yellowstone river valleys from Soda Butte to Gardiner, Montana. It also migrates outside of the park into the Gallatin National Forest and onto private lands.
Elk on the northern range
After decades of debate over whether this range was overgrazed by too many elk, public concern has shifted to the herd's small size. The winter count, which was approximately 17,000 when wolf reintroduction began in 1995, fell below 10,000 in 2003. It fluctuated between 6,000 and 7,000 as the wolf population on the park's northern range declined from 94 in 2007 to 38 in 2010. The elk count dropped to 3,915 in early 2013, the lowest since culling ended in the park in the 1960s. The decrease has been attributed to predation by reintroduced wolves and a large bear population, hunter harvest, and droughtrelated effects on pregnancy and survival. The State of Montana has reduced the permits issued for this herd so that hunting of females now has little impact on population size.
There are some indications that elk–wolf interactions are contributing to a release of willows and other woody vegetation from the effects of herbivory on the northern range. Wolves have altered the group sizes, habitat selection, movements, distribution, and vigilance of elk while the proportion of browsed aspen, cottonwood, and willow leaders has decreased in some areas during recent years, and cottonwood and willow heights have increased significantly. Research is underway to determine how climate, hydrology, wolf predation/avoidance, and herbivory interact in their effects on these woody species.
Elk in the interior
Elk in the Greater Yellowstone Ecosystem
Elk in areas burned by wildfire
Disease in Greater Yellowstone
The prevalence of brucellosis in Yellowstone elk is low; the rate of exposure to brucellosis in 100 adult female elk captured on the park’s northern range during the winters of 2000 to 2005 was 2 percent; it was 3 percent in 130 neonatal elk on the park’s northern range during the summers of 2003–2005; and it was 3 percent in 73 adult female elk captured in the park’s Madison–Firehole drainages during winters of 1996–1998. Elk are commonly observed within 100 yards of bison during late winter and spring when brucellosis-induced abortion or calving occurs in Yellowstone.
Because of their high densities, elk that are fed in winter have sustained high levels of brucellosis; winter feeding on the northern range stopped more than 50 years ago. Elk are fed during the winter at the National Elk Refuge in Jackson, Wyoming, in addition to 22 Wyoming-run feedgrounds. The feedgrounds were created in the 1900s to maintain Wyoming’s elk herds and limit depredation as migratory routes from summer range to lower elevation winter ranges became blocked by settlement in the Jackson area. Transmission of brucellosis from feedground elk, where an average of 30 percent have tested positive for exposure to the bacteria, was the apparent source of infection in Wyoming cattle in 2004.
Chronic wasting disease