Sitka Black-tailed Deer

Sitka Black-tailed Deer

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Description

The Sitka black-tailed deer is smaller, stockier and has a shorter face than other members of the black-tailed group. The summer coat of reddish-brown is replaced by dark brownish gray in winter. Antlers are dark brown with typical black-tailed deer branching. Normal antler groth is three points (including the eyeguard) on each side. Antlers are relatively small.

Lifestyle

Sitka deer have a vertical migration pattern up and down the mountains in their range, traveling up higher in summer and moving to low elevations in winter.  The following pattern is seen in Sitka deer in the coastal mountains and forests of Southest Alaska:

Late spring (1,500 feet elevation):  Fawns are born in May and June, often twins. In late spring, deer feed on new plants in forests up to 1,500 feet.  As snow melts, many bucks and yearlings move to higher elevations. Does females) and fawns (young deer) stay in lower forests to feed in openings clear of snow.

Summer (3,000 feet elevation):  Deer that move into the mountains reach sub-alpine meadows in July, up to 3,000 feet. They eat nutritious plants growing among small trees.

Fall (1,500 feet elevation):  Deer at higher elevations begin to move down into lower forests in September, at the first sign of frost.  Bucks (males) enter the rut, or breeding season, in October and November. Their focus switches from feeding to breeding during this time.

Winter (below 1,000 feet):  During winter, deer stay in old-growth spruce and hemlock forests on southern slopes, usually below 1,000 feet. These forests have a high tree canopy which catches falling snow while still providing enough light for plant growth, providing the perfect balance between energy use and food access.

Food Habits

During summer, deer generally feed on herbaceous vegetation and the green leaves of shrubs.  In winter, they are restricted to evergreen forbs and woody browse.  They prefer evergreen forbs such as bunchberry and trailing bramble. During periods of deep snow, they eat woody browse such as blueberry, yellow cedar and hemlock, and arboreal lichens.  They rarely eat grass.

Lifecycle

Sitka deer fawns are born in late spring, following the breeding season in late November.  Breeding bucks spend little time foraging and by late November have used up much of their fat reserve, while does generally enter December in prime condition.  Does breed during their second year of life and continue producing fawns annually until they reach ten or twelve years of age.  Prime-age does, five to ten years old, typically produce two fawns annually.

Population Status, Threats & Conservation

The conversion of forests from uneven-aged, old-growth to even-aged new-growth causes concern for the future carrying capacity of this deer species, especially with the levels of snow accumulation in their habitat.  Even-aged new-growth forests produce very little forage for deer as they mature, due to the dense overstory and lack of adequate understory growth.  At less than 20 years of growth, these open areas do allow for good plant growth for deer, however it is unavailable to them as snow covers the open areas in winter.  Old growth, uneven-aged forests have a canopy coverage that has the perfect mixture of snow depth reduction (by interception) and also available light for plant growth.  This balances the deer’s energy expenditure (less work if snow is not deep) with intake, especially in winter.

Deer use more energy to travel and find food in deep snow. When snow is deeper than 10 inches, they must conserve energy by moving shorter distances to find food. If snow is deeper than 12 inches, plants and shrubs become buried and deer struggle to find food. They also become more vulnerable to predators. Spring is a critical time, as deer can die of starvation if snow stays late in the season.

While deer populations are stable in Alaska, their future is connected to the preservation of lower elevation old-growth forests. This habitat is critical to their winter survival in Southeast Alaska. An old-growth forest reaching an age of 500 years or more provides great variation in tree canopy and levels of understory plant growth for deer. When these forests are cleared and young forests grow, the uniform and dense tree canopy chokes out understory plants. This means a lack of food for deer in these areas.

Sources:
U.S. Forest Service:  Relationships between Sitka black-tailed deer and their habitat, Hanley, 1984
Alaska Department of Fish and Game, Sitka black-tailed deer species profile