Elk are among the most
gregarious deer species. Cows produce an alarm bark to alert other members of the herd to danger, while calves will produce a high-pitched scream when attacked.
Reproduction and life cycle Female elk have a short
estrus cycle of only a day or two, and matings usually involve a dozen or more attempts. By the autumn of their second year, females can produce one and, very rarely, two offspring. Reproduction is most common when cows weigh at least . Dominant bulls follow groups of cows during the
rut from August into early winter. A bull will defend his harem of 20 cows or more from competing bulls and predators. A male elk's urethra points upward so that urine is sprayed almost at a right angle to the penis. The urine soaks into their hair and gives them a distinct smell which attracts cows. A bull interacts with cows in his harem in two ways: herding and courtship. When a female wanders too far away from the harem's range, the male will rush ahead of her, block her path and aggressively rush her back to the harem. Herding behavior is accompanied by a stretched out and lowered neck and the antlers laid back. A bull may get violent and hit the cow with his antlers. During courtship, the bull is more peaceful and approaches her with his head and antlers raised. The male signals his intention to test the female for sexual receptivity by flicking his tongue. If not ready, a cow will lower her head and weave from side to side while opening and closing her mouth. The bull will stop in response in order not to scare her. Elk calves are as large as an adult
white-tailed deer by the time they are six months old. Elk will leave their natal (birth) ranges before they are three years old. Males disperse more often than females, as adult cows are more tolerant of female offspring from previous years. Elk live 20 years or more in captivity but average 10 to 13 years in the wild. In some subspecies that suffer less predation, they may live an average of 15 years in the wild.
Migration in Jackson Hole, Wyoming, after migrating there during the fall As is true for many species of deer, especially those in mountainous regions, elk
migrate into areas of higher altitude in the spring, following the retreating snows, and the opposite direction in the fall. Hunting pressure impacts migration and movement. During the winter, they favor wooded areas for the greater availability of food to eat. Elk do not appear to benefit from thermal cover. The Greater Yellowstone Ecosystem elk herds comprise as many as 40,000 individuals. During the spring and fall, they take part in the longest elk migration in the continental U.S., traveling as much as between summer and winter ranges. The Teton herd consists of between 9,000 and 13,000 elk and they spend winters on the
National Elk Refuge, having migrated south from the southern portions of
Yellowstone National Park and west from the
Shoshone and
Bridger–Teton National Forests.
Diet Elk are ruminants and therefore have four-chambered stomachs. Unlike white-tailed deer and moose, which are chiefly browsers, elk are similar to
cattle in that they are primarily
grazers. But like other deer, they also
browse. Elk have a tendency to do most of their feeding in the mornings and evenings, seeking sheltered areas in between feedings to digest. Their diets vary somewhat depending on the season, with native grasses being a year-round supplement, tree bark (e.g.
cedar,
wintergreen,
eastern hemlock,
sumac,
jack pine,
red maple,
staghorn, and
basswood) being consumed in winter, and
sedges,
forbs, and tree sprouts during the summer. Favorites of the elk include
dandelions,
aster,
hawkweed,
violets,
clover, and the occasional
mushroom. Particularly fond of
aspen sprouts which rise in the spring, elk have had some impact on aspen groves which have been declining in some regions where elk exist. Range and wildlife managers conduct surveys of elk pellet groups to monitor populations and resource use. Research in the
Greater Yellowstone Ecosystem has found that supplemental feeding of concentrated
alfalfa pellets leads to significant alterations in the elks'
microbiome. The elk gut microbiome is typically characterized by a diverse community of bacteria specialized in breaking down complex plant fibers and
cellulose, whereas the supplementally fed gut microbiome may have less fiber-digesting bacteria. Therefore, transitioning from natural foraging to concentrated alfalfa pellets can cause changes in the gut microbiome that might affect the elk's ability to efficiently digest their natural diet or could potentially lead to imbalances that affect overall health.
Coyote packs mostly prey on elk calves, though they can sometimes take a winter- or disease-weakened adult. In the
Greater Yellowstone Ecosystem, which includes Yellowstone National Park, bears are the most significant predators of calves while healthy bulls have never been recorded to be killed by bears and such encounters can be fatal for bears. The killing of cows in their prime is more likely to affect population growth than the killing of bulls or calves. Elk may avoid predation by switching from grazing to browsing. Grazing puts an elk in the compromising situation of being in an open area with its head down, leaving it unable to see what is going on in the surrounding area. Living in groups also lessens the risk of an individual falling to predation. Large bull elk are less vulnerable and can afford to wander alone, while cows stay in larger groups for protection for their calves.
Parasites and disease At least 53 species of
protist and animal
parasites have been identified in elk. Most of these parasites seldom lead to significant mortality among wild or captive elk.
Parelaphostrongylus tenuis (brainworm or meningeal worm) is a parasitic
nematode known to affect the spinal cord and brain tissue of elk and other species, leading to death. The definitive host is the white-tailed deer, in which it normally has no ill effects. Snails and slugs, the intermediate hosts, can be inadvertently consumed by elk during grazing. The
liver fluke Fascioloides magna and the nematode
Dictyocaulus viviparus are also commonly found parasites that can be fatal to elk.
Chronic wasting disease, transmitted by a
misfolded protein known as a
prion, affects the brain tissue in elk, and has been detected throughout their range in North America. First documented in the late 1960s in mule deer, the disease has affected elk on game farms and in the wild in a number of regions. Elk that have contracted the disease begin to show weight loss, changes in behavior, increased watering needs, excessive salivation and urinating and difficulty swallowing, and at an advanced stage, the disease leads to death. No risks to humans have been documented, nor has the disease been demonstrated to pose a threat to domesticated cattle. In 2002,
South Korea banned the importation of elk antler velvet due to concerns about chronic wasting disease. The
Gram-negative bacterial disease
brucellosis occasionally affects elk in the Greater Yellowstone Ecosystem, the only place in the U.S. where the disease is still known to exist, In domesticated cattle, brucellosis causes infertility, abortions, and reduced milk production. It is transmitted to humans as
undulant fever, producing
influenza-like symptoms that may last for years. Though bison are more likely to transmit the disease to other animals, elk inadvertently transmitted brucellosis to horses in Wyoming and cattle in
Idaho. Researchers are attempting to eradicate the disease through vaccinations and herd-management measures, which are expected to be successful. Nevertheless, research has been ongoing since 2002, and a successful vaccine has yet to be developed . A recent
necropsy study of captive elk in Pennsylvania attributed the cause of death in 33 of 65 cases to either gastrointestinal parasites (21 cases, primarily
Eimeria sp. and
Ostertagia sp.) or bacterial infections (12 cases, mostly
pneumonia). Elk hoof disease was first noticed in the state of Washington in the late 1990s in the
Cowlitz River basin, with sporadic reports of deformed hooves. Since then, the disease has spread rapidly with increased sightings throughout southwest Washington and into Oregon. The disease is characterised by deformed, broken, or missing hooves and leads to severe lameness in elk. The primary cause is not known, but it is associated with
treponeme bacteria, which are known to cause
digital dermatitis in commercial livestock. The mode of transmission is also not known, but it appears to be highly contagious among elk. Studies are being undertaken by government departments to determine how to halt or eliminate the disease. ==Distribution and status==