Moose - Morphology
Moose exhibit a distinct sexual dimorphism in regard to body mass.
Males can reach a maximum size of 1,650 pounds (750 kg) while females
have a maximum weight of 1,100 pounds (500kg). However, females
typically average between 880 and 990 pounds (400-450 kg) and males
average between 1,435 and 1,545 pounds (650-700 kg). Females achieve
maximum weight in early winter and around age 4, while males achieve
maximum weight just before breeding season and between ages 7 and 9.
Moose grow their entire lives, but no significant weight is gained after
4 years for females and after 9 years for males. As they grow older and
begin to senesce, they lose body mass and become smaller. Weight change
over time is also variant depending upon forage availability per year.
Bull moose lose 12 to 19 percent of their pre-rut body size during the
breeding season, and 7 to 23 percent of pre-rut body size during winter.
They will subsequently gain 33 to 41 percent of post winter lows (in
weight) during the summer. Conversely, females live by a completely
different schedule. They are at minimum weight shortly after giving
birth which averages about 77 pounds lost birthing a single calf and
nearly 140 pounds lost birthing twins. Gains in summer average 25 to 43
percent with 2-year olds gaining the most weight.
Length is incredibly variable and not well documented in the different
subspecies throughout the country. No data is available on the
Yellowstone Moose (Alces alces shirasi
Nelson (1914)) but the Eastern Moose (
Alces alces Americana
Clinton (1822)) and Northwestern Moose (
Alces alces andersoni
Peterson (1952)) have a total length of equal or greater than 9.2 feet
(280 cm) and a shoulder height of 6.1 to 6.4 feet (185-195 cm). The
Alaskan/Yukon Moose (
Alces alces gigas
Miller (1899)) is slightly
larger with a total length of 9.3 to 10 feet (283-306 cm) and a
shoulder height of 6.2 to 7 feet (190-212cm).
Moose coats range within the spectrum of brown shades but have been
known to be black, rusty, and even albino or mottled on occasion. The
hue will change depending on season. Bull moose typically develop a
darker toned face during the fall due to male sex hormones. During
winter, moose will exhibit a lighter colored coat. After winter, moose
will take on a shabby appearance as they begin to molt. The frail,
lighter hair will be shed, causing patches of dark skin on the head and
shoulders to be bared. In the beginning of the summer, adults will have
regrown their typical dark, glossy coat. Newborn calves have a tendency
to have a rust colored coat of hair.
Photo Credit:US Fish and Wildlife Service
The coat is formed from two layers. The long, course hair, or guard
hair, and the short, dense, wooly, bottom hair work simultaneously to
regulate the moose’s body temperature. The hide also helps in regulating
body temperature and protects the flesh from injury. The sebaceous
glands secrete an oily/waxy matter called sebum to lubricate and
waterproof the hair and cause it to remain supple, further increasing insulation. Sweat
glands help to moisten the insulation properties of the skin and
regulate internal temperature during the summer.
Antlers, formed from solid bone, are the key feature to sexing moose.
Only bull moose exhibit antlers which can also be used to estimate an
individual’s age. Typically, the oldest bull will boast the largest
antlers. The size and shape also signify social dominance among bulls.
Bulls will thrash brush or lock antlers and fight by pushing against
other males to gain dominance. Antlers are covered in velvet which is
rubbed off prior to the antlers being shed in November each year.