Deer in Northern Maine – Summary & Recommendations for Management
by Steve Young
Certified Wildlife Biologist, USDA NRCS TSP - Wildlife CAP
The primary limiting factor for White-tailed deer is quality winter habitat to sustain them during critical winter conditions. When the sinking depth of snow exceeds the length of their legs, their movement and ability to access food is greatly restricted. The period of restrictive snow to deer in Maine commonly reaches 80 to over 100 days in northernmost Maine. Exposure to cold weather conditions is taxing to deer condition, and only cedar, hemlock, and litterfall from mature non-plantation softwood provide quality food to deer in winter. Shelter and access to these food sources are essential to sustaining deer in Northern Maine. Deer congregate to seek shelter “yard” in mature natural softwood dominated forest areas. Most deer yards contain low-lying softwood-dominated forest containing some riparian area, and ideally having some southern exposure. Forest stands with high crown closure provide more stable temperature and humidity conditions, lower snow depths, and shelter from the wind.
Deer typically use about 10-15% of their range in winter, commonly travel 20 miles or more between from summer and winter range. Yearling deer follow their mothers to wintering areas, and thereafter, show strong fidelity to return to the same area in subsequent years unless attracted or deterred by active forestry operations, or artificial feeding. Deer feeding can cause a variety of problems including attracting deer away from quality habitat, increasing incidents of vehicle-deer collisions, potential disease issues from concentrated feed around feces (worst case chronic wasting disease), and nutritional problems from use of poor feed.
Deer show strong preference to forest stands containing Northern White Cedar, proximity to which was the most significant factor in determining deer activity in published research conducted in Plaster Rock, New Brunswick. Cedar, which occurs as a dominant forest community type in some low-lying riparian areas in Northern Maine, provides shelter and high food values and is very long-lived, reaching ages of 400 years or more. Eastern Hemlock also provides high value to deer, and even better shelter values.
Deer are also attracted to hardwood branches within reach to browse such as maples, however, it is of very low nutritional value to wintering deer. Balsam Fir, though not a preferred food, is also browsed by deer in absence of other foods and provides good shelter value. Fir is a short-lived species, rarely exceeding 90 years of age in Maine, and is very unstable after partial harvests in pure stands over 45 years of age. Older natural softwood stands provide valuable “litterfall” of twigs, foliage, and lichens which fall from tree tops during the winter. Litterfall has lower levels of tannins and lignins than are found in branches within reach of deer, which results in more palatable and high value food.
Though low-lying softwoods provide best protection from wind and weather, solar aspect is also important to deer, and they prefer areas that provide southern exposure. It is noteworthy that deer may also use the north side (south facing) slopes of east-west running valleys adjacent to waterways regardless of forest type. Even though they do not provide winter cover, even pure hardwood stands may be used by deer when the solar exposure & nightly cooling, and wind create snow conditions that deer can traverse without sinking deep. (This has been observed on several occasions during winter aerial surveys along the Right Hand Branch of the Tobique River, and in the Green River area north of Edmundston).
Deer usually enter their wintering areas (yards) in early December, and establish trail systems to access food. When deer numbers are low, trails systems require more energy to establish and maintain, and early deep snow can significantly reduce the amount of trails that are established in a particular winter. Carrying capacity of winter habitat is dependent on the value of shelter and available food (including litterfall), and extended restriction by deep snow leads to high mortality of deer, especially yearlings, and also to death and re-absorption of unborn fawns. After severe winters, the number of fawns, especially twins, is greatly reduced. In New Brunswick, deer habitat carrying capacity is estimated in deer days per hectare, usually estimated at about 18 deer days per hectare. At a yarding period of 100 days in northernmost Maine, this roughly equates to about 5 hectares or 10 acres required per deer. This represents average habitat conditions, and quality habitat with significant cedar and hemlock components can support higher densities. Significant mortality in deer occurs after deer leave their wintering areas on route to their summer range as deer are often in poor condition after the winter and are susceptible to predation, particularly in an intensively managed or developed landscape. Patches of forest interspersed on the landscape provide important refuge for deer as they travel between winter and summer ranges, and well stocked forest of any type provides valuable habitat to deer in avoiding predators and accessing food. Deer utilize a variety of herbaceous plants and foliage of deciduous trees during summer, which can be greatly enhanced by promoting food producing herbaceous and woody vegetation.
Deer usually give birth to fawns in early June, and are known to use Silver Maple floodplain habitat that provide both food and shelter values during that period. Depletion of this habitat type likely increase their susceptibility to predation by bears and other predators that frequent this habitat type in the spring.
Larger wintering areas are better than smaller ones, with the best areas being 1,000 acres or more, however, habitat areas as small as 10 acres may support deer that for whatever reason are unable to reach their wintering areas to survive the winter (such as being stranded by early restrictive snow, or if their wintering areas have been depleted. Habitat areas interspersed along the landscape along riparian areas will to both support wintering deer, and forested parcels of any type, including hardwood, will provide habitat for deer in summer.
Even in relatively fast growing forest stands such as Balsam Fir, winter deer habitat only begins when the stand is about 35 or 40 years old, which requires longer rotation forest management to provide sustainable habitat in a particular area. For example, to sustainably sustain 50% of a particular forest parcel in winter habitat that starts at 40 requires a minimum rotation of about 80 years. It should be noted that spruce plantations are almost never used by wintering deer, presumably because of a lack of food.