The Alaska-Yukon race (Alces alces gigas) is the largest of all the moose. Adult males are larger than the females and in prime condition weigh from 1,200 to 1,600 pounds. Adult females weigh 800 to 1,300 pounds.
Only the males or “bulls” have antlers. Most male calves develop a hair-covered, bony protuberance by the end of summer that persists through their first year. Following this initial development, antlers are grown each summer and shed during winter throughout the bull’s life. The largest moose antlers in North America come from Alaska, the Yukon Territory, and the Northwest Territories of Canada. Trophy age class bulls with antlers 50 inches in spread or larger are found throughout Alaska. Moose occasionally produce trophy-size antlers when they are 6 or 7 years old, with the largest antlers grown at approximately 10 to 12 years of age. Moose rarely live more than 16 years.
Growth patterns, age at sexual maturity, and production of offspring are closely tied to range conditions. Female or “cow” moose generally breed at 28 months, though some may breed as young as 16 months. Calves are born any time from mid-May to early June after a gestation period of about 230 days. A cow moose defends her newborn calf vigorously. Cows give birth to twins 20-45 percent of the time, and triplets may occur. Newborn calves generally weigh 28 to 35 pounds and rarely as much as 45 pounds. Calves begin nursing within the first few hours following birth and take solid food a few days later. During their first 5 months, while suckling and foraging, calves will grow to more than 10 times their birth mass; occasionally weighing more than 500 pounds. Calves are generally weaned in the fall at the time the mother is breeding again.
The maternal bond is generally maintained until calves are 12 months old at which time the mother aggressively chases her offspring from the immediate area just before she gives birth. Moose breed in the fall with the peak of the “rut” activities coming in late September and early October. Adult males joust during the rut by bringing their antlers together and pushing. Serious battles are rare, but bulls regularly receive a few punctures, sometimes break ribs, and occasionally die from their wounds. The winner usually mates with several females.
By late October, adult males have exhausted their summer accumulation of fat and their desire for female company. Once again they begin feeding. Antlers from mature bulls are shed as early as November, but mostly in December and January. Young bulls may be seen with their antlers as late as April. Most moose make seasonal movements to calving, rutting, and wintering areas. They travel anywhere from only a few miles to as many as 60 miles during these transitions.
Moose have a high reproductive potential and can quickly overpopulate a range if not limited by predation, hunting, and severe weather. Deep crusted snow can lead to malnutrition and subsequent death of hundreds of moose and decrease the survival of the succeeding year's calves.
Moose are killed by wolves, black and brown bears. Black bears take moose calves in May and June. Brown bears kill calves and adults the entire time the bears are out of their winter dens. Wolves kill moose throughout the year. Predation limits the growth of many moose populations in Alaska.
