More info for the terms: cover, density, dispersion, fire management, forbs, hardwood, mast, natural, prescribed fire, presence, shrub, shrubs, succession, tree
Disturbance can produce habitat for mule deer by favoring forage growth and by creating ecotones between areas of dense cover and more open feeding areas. Conversely, loss of cover over large areas can be detrimental to mule deer [135,215]. Several researchers suggested that resource managers may need to consider proximity of food, cover, and water before implementing actions that may impact mule deer habitats [153,215,216].
Prescribed fire: For information on the use of prescribed fire in mule habitats, see Fire Management Considerations.
Logging: With the exception of black-tailed deer in British Columbia and southeastern Alaska, which are dependent upon canopy cover in mature forests [134,135,215,325,350], mule deer generally benefit from early successional vegetation that establishes after logging and other disturbances [135,215]. Logging may benefit mule deer because early-seral habitats often contain a greater variety, quantity, and quality of mule deer forage than mature forests (e.g., [39,72,98,137,269,290,304,310,325,349]). However, forage quantity and quality may not increase immediately in logged areas and may last only 20 to 30 years (e.g., [134,147,215,269,310,350]). In addition, cover may be reduced [310]. A review stated that clearcutting of old-growth forests in southeastern Alaska has 4 potential effects may decrease the carrying capacity of habitat for black-tailed deer: 1) sun-grown plants in open clearcuts may have lower digestible protein concentrations than shade-grown plants in forests; 2) large amounts of logging slash may increase energy costs of locomotion for black-tailed deer and reduce the area of usable habitat; 3) snow may accumulate and persist more in open clearcuts than in forests; and 4) understory production may be reduced to extremely low levels when the conifer canopy closes; this may occur at about 20 to 30 years after logging and persist for 100 years or more [134].
In general, the duration of logging benefits to mule deer varies with forest type, soils, climate, and other factors. Use of prescribed fire, herbicides, soil scarification, planting of seeds and seedlings, and other site preparation may shorten or lengthen the time a logged site is used by mule deer [134,147,215]. For example, burning young clearcuts in southeastern Alaska may benefit black-tailed deer by reducing shrub and conifer biomass and increasing the diversity of herbaceous forage plants, thus potentially delaying conifer canopy closure [134]. In addition, succession following clearcutting may be affected by heavy mule deer browsing. For more information, see Mule deer foraging effects. Mule deer use of logged areas is modified by opening size, logging slash, predisturbance movement patterns, and weather, particularly snow depth. Reviews of logging effects on mule deer are available: [72,134,351].
Opening size: The size and distribution of clearcuts in space and time are important to mule deer; this is likely also true of burned sites. In the boreal forest zone in western Alberta, the size and dispersion of 2- to 9-year-old clearcut blocks and type of treatment best explained mule deer and white-tailed deer use of clearcuts (R²=0.21, P<0.01). Deer showed a strong preference for clearcut blocks that were <40 acres (16 ha); because they preferred areas within clearcuts that were <330 feet (100 m) from cover, they favored configurations that provided a high degree of edge per unit area. They also preferred clearcuts that were scarified or scarified and burned under prescription compared with untreated clearcuts. The authors suggested that such treatments may have led to greater abundance of preferred herbaceous species and reduced logging slash, which benefited deer. Clearcut blocks in clumped patterns appeared unfavorable [334]. Some authors suggested that many small, scattered, irregularly shaped clearcuts may be preferable to fewer, large, block-shaped clearcuts because multiple small treatments would contact the home ranges of more mule deer [135,334]. A review stated that deer used natural and created openings in ponderosa pine forests similarly, particularly when thinned stands occurred nearby, but in dense stands, deer likely benefited from small openings [72]. For more information, see Edge habitat. See the review by Wallmo and Schoen [351] for management recommendations regarding sizes of clearcut openings in various regions.
Logging slash: Depending upon its density, logging slash may be a benefit or a detriment to mule deer. Reviews stated that abundant logging slash generally impedes mule deer movements and may act as a barrier to mule deer use of clearcut openings and selectively logged areas [63,135,351]. Conversely, some logging slash can provide cover for mule deer [351]. In quaking aspen stands on the Apache and Coconino National Forests, Arizona, deer use was lower in thinned quaking aspen stands without slash removal despite greater density of perennial grasses, forbs, and quaking aspen sprouts in these stands compared to unthinned stands. Apparently, the amount of woody debris in thinned stands prohibited deer use [268]. In southeastern Alaska, dense logging debris apparently impeded black-tailed deer use of 1- to 2-year-old clearcuts in western hemlock-Sitka spruce forest. Dense logging debris continued to impede black-tailed deer until 15 to 20 years after logging [350]. Mule deer pellet group counts in clearcut strips in subalpine lodgepole pine and spruce-fir forest in Colorado were less than those on adjacent uncut sites during the first year after logging, possibly due to the deep tangle of residual slash and disturbance of logging operations. However, 10 years after strip clearcutting, pellet group counts were 2 times higher on clearcut strips than on adjacent uncut strips [344]. In a selectively cut ponderosa pine forest in Arizona, deer pellet groups were more numerous where slash was undisturbed after logging. Slash abundance was 1.7 times greater where slash was undisturbed than where it was piled and burned, but forbs were more abundant where slash was piled and burned, which should have attracted deer. The author suggested that deer may have preferred the site where slash was undisturbed because the slash provided protective cover [266]. In north-central Arizona, mule deer use was higher on clearcuts where the slash had been piled and burned than on clearcuts where slash had been piled but not burned [189]. In Arizona, Neff (1980 cited in [72]) found that deer showed no preference for either the presence or absence of slash in small (1-10 acres (0.4-4.0 ha)) openings in ponderosa pine stands.
A review recommended prescribed fire in southeastern Alaskan forests after clearcutting to reduce logging slash, reduce shrub biomass, favor herbs, reduce conifer regeneration, and prolong the useful life of clearcuts for mule deer, at least in snow-free seasons or areas [135]. In juniper woodlands in Texas, Bryant [57] suggested that 10% to 15% of cleared areas should contain slash to provide cover for mule deer. Black-tailed deer may also benefit from reduced logging slash that potentially impedes their movements [134]. For more information, see Indirect Fire Effects.
Logging and weather interactions: Mule deer may not use clearcuts because of deep snow compared to forests [357]. In the interior western redcedar-western hemlock subzone near Horsefly, British Columbia, mule deer tracks during a year of low snowfall were half as abundant in clearcuts as in uncut forest. Snow was 17 inches (44 cm) deep in openings and just 10 inches (26 cm) deep in forests, suggesting that deep snow in clearcuts may have reduced forage access and thus use of clearcuts [357]. For more information, see Foraging sites.
Other treatments:
Sagebrush and pinyon-juniper: Removal of shrubs and trees in sagebrush and pinyon-juniper ecosystems is a common management practice on mule deer rangelands. In sagebrush and pinyon-juniper ecosystems, large areas have been treated mechanically, with prescribed fire, or with herbicides to try to convert them to grass-shrub or grass types [66,347]. Such treatments in sagebrush communities may reduce important winter forage for mule deer [91]. Partial or complete removal of trees in pinyon-juniper communities may result in substantial increases in production of grasses, forbs, and shrubs, which could potentially increase mule deer carrying capacity [66], but according to a review, this practice produces mixed results. Some studies showed increased mule deer use of treated pinyon-juniper sites, typically due to greater amounts of forage and browse on treated areas, while other studies did not show increased mule deer of treated areas, typically because of reduced cover in these areas [2]. On the Zuni Indian Reservation in western New Mexico and eastern Arizona, mule deer pellet groups increased with the number of pinyon and juniper trees removed (R²=0.95, P=0.03) [2]. A similar increase did not occur on 2- to 24-year-old pinyon-juniper rangelands in Utah that were chained and seeded with grasses, forbs, and shrubs. The authors suggested that treated sites were used despite decreased cover because of increased forage [299]. At Fort Bayard, New Mexico, mule deer abundance in Colorado pinyon (Pinus edulis)-juniper habitat was higher before than after tree removal. Mule deer forage increased after tree removal, but the authors concluded that the absence of cover reduced mule deer use [294]. In a review, Phillips [256] stated that chained pinyon-juniper stands did not benefit mule deer and other wild ungulates until trees and shrubs established [299]. Other researchers reported that treatment of pinyon-juniper rangelands did not affect mule deer habitat use. Mechanical and herbicide treatments on 5,200 acres (2,100 ha) of pinyon-juniper rangeland in Arizona resulted in no differences in mule deer use of the area (Neff 1980 cited in [290]).
Mule deer use pinyon-juniper woodlands in all stages of succession [2]. How long each stage is utilized depends in part on site, composition of the understory prior to disturbance, the type of disturbance, weather conditions, postdisturbance treatments such as seeding, and livestock grazing [290]. In general, the usefulness of pinyon-juniper habitats to mule deer declines as the understory and midstory decline [295]. Based upon studies in west-central Utah, posttreatment production of forbs and grasses generally diminishes to pretreatment levels in <20 years; shrubs increase up to 40 years after treatment; and at 40 years, juniper and pinyon again dominate the site [21]. In Nevada, annual and perennial forbs dominated for 1 to 2 years after canopy removal; perennial grasses dominated in the 2nd year and reached maximum abundance in the 4th year. Shrubs reached a peak after grasses, between the 1st and 3rd posttreatment years, and trees regained dominance in <15 years [329].
According to a review, published literature is "nearly unanimous" in recommendations for pinyon-juniper management for mule deer and other wild ungulates: 1) keep openings small and close to escape cover, usually 0.1 to 0.2 mile (0.16-0.32 km) maximum; 2) locate projects near areas of historical big game usage; and 3) leave browse plants untreated or reestablish following treatments [2]. These authors provide management recommendations for mule deer and other ungulates in pinyon-juniper communities: [57,290,295]. See Great Basin woodlands for information about fire effects on mule deer in pinyon-juniper communities. For a review of the effects of management practices in sagebrush steppe on mule deer—including topics not discussed here such as management of sagebrush with herbicides, fertilizing sagebrush habitats, and reseeding after sagebrush reduction—see Carpenter and Wallmo [66]. See Great Basin shrublands for information about fire effects on mule deer in sagebrush communities.
Gambel oak: Gambel oak is an important mule deer forage species; both its mast and browse are used extensively. It may form almost pure stands in some areas. Because of its growth habit, however, it often forms impenetrable thickets that are too tall or inaccessible for mule deer [66,186]. Methods used to treat Gambel oak communities include prescribed fire, logging, and herbicides. Clearcutting patches in Gambel oak habitat may produce abundant browse because of Gambel oak's sprouting ability, but this would temporarily reduce acorns. Selective cutting, in which the best acorn-producing trees are left, was recommended by Severson and Medina [290] to ensure both browse and acorn production at a single location. A review stated that treating Gambel oak stands with prescribed fire or mechanical methods may increase mule deer use of treated stands up to 4 times but that use declines as time since treatment increases and stands become dense and inaccessible [186]. In Colorado, dense Gambel oak stands were sprayed with herbicides. Two years after spraying, grasses increased 44% compared with pretreatment levels, while shrubs decreased 29% and forbs decreased 15%. Five years after spraying, grasses were 17% below pretreatment levels and shrubs were 7% below pretreatment levels. Consequently, herbicide treatment was considered beneficial to mule deer for only a brief time, and frequent retreatment was considered necessary to maintain high-quality habitat for mule deer [180]. See Southwest shrublands for information about fire effects on mule deer in Gambel oak communities.
Livestock grazing: Influences of livestock grazing on mule deer can be detrimental, neutral, or beneficial [67,153,216,290]. Grazing, as well as the physical presence of cattle, domestic sheep (Ovis aries), and other livestock can have negative impacts on mule deer not only by reducing forage and changing ratios of live to dead plant material [8,153,290,361,362], but by causing changes in movements and behavior and altering activity budgets [67,67,169,216,263,290]. However, some researchers reported few or no effects of livestock grazing on mule deer in areas where livestock grazing intensity was low or moderate [18,67,153,290]. Livestock grazing in many perennial grasslands historically increased shrub and annual grass-forb types, potentially benefiting mule deer (see Threats) [153,216,290]. In other areas, heavy livestock grazing reduced shrubs and herbs important as mule deer forage [216]. Reviews noted that livestock grazing on the northern Great Plains has extensively reduced or eliminated hardwood tree and shrub cover along drainageways, which has limited the occurrence of mule deer in some areas [287,290]. In the Sierra Nevada, cattle grazing during peak fawning season reduced hiding cover for fawns in both quaking aspen and meadow-riparian habitats compared with areas without cattle grazing [169,197]. Reviews stated that livestock management practices and factors that may affect mule deer include weather, topography, water availability, rangeland type, grazing intensity, animal distribution, livestock species, grazing system, and timing and duration of grazing. Timing of livestock grazing was considered particularly important to mule deer, which are particularly susceptible to adverse effects during fawning [17,67,153,169,215,216,290,290].
Water management: On some arid ranges of the Southwest, water development and better distribution of water sources for livestock can benefit mule deer by permitting year-round or seasonal use of rangelands from which they may have been excluded by a lack of free water (see Water) [153,215,216,280]. Mule deer numbers increased during the 5 years following development of permanent water sources on areas of Fort Stanton, New Mexico, that had little or no free water previously. In one area, use increased from <1.6 to >13 mule deer/mile² in 5 years. In another area, use increased from 14.2 to 19.2 mule deer/mile² in 1 year, dropped to 9.4 mule deer/mile² in the 4th year when water sources deteriorated, and increased to 22.1 mule deer/mile² in the 5th year when water was again available [367]. However, water developments may concentrate livestock and deer, leading to degradation of some habitats [153,215,216]. Furthermore, redistribution of livestock through water development may increase overlap of mule deer and livestock on areas previously occupied by mule deer but not livestock [153,216]. For more information, see the review by Mackie and others [215].