HABITAT
Conifer forests, shrub terrain with aspen stands, sagebrush steppe,  grasslands, and adjacent to agricultural lands.

TASTE
Lean rich meat, flavor somewhere between beef and lamb. Good to excellent table fare.

ABUNDANCE
Excellent populations.

LICENSE, TAGS AND PERMITS NEEDED
Valid Idaho hunting license and deer tag. Archery permit if hunting in archery only season. Muzzleloader permit if hunting in muzzleloader only season.

Mule Deer

HABITAT
Idaho’s mule deer habitat is highly diverse and variable. With elevation gradients spanning 11,952 ft (710–12,662 ft), annual precipitation ranging from 6 to 104 inches, and temperature varying more than 120° F during the year, vegetation types vary considerably. Mule deer exploit this diversity, improving their chances for survival. Maintaining intact productive habitats on summer range, winter range, and migratory pathways is paramount for ensuring long-term sustainability of Idaho’s mule deer herds. These essential seasonal habitats are all affected to varying degrees by ecological succession, forest management, wildfire, climate change, invasive and noxious weeds, and human development.

SUMMER RANGE

Mule deer seek higher elevations with abundant food to raise offspring and increase fat reserves during summer. A deer’s ability to survive harsh winter conditions is directly related to the amount of reserves obtained on summer range. Much of Idaho’s mule deer summer range occurs on U. S. Forest Service (USFS) lands dominated by pine and fir forests that vary in productivity. The most productive forests are those in early and mid-successional stages. Reduced summer-range productivity in some locations has resulted from recent reductions in timber harvest rates, reduced wildfire frequency, increased wildfire severity, increased human development, and increased prevalence of invasive and noxious weeds.

Late-successional conifer forests provide little forage for mule deer, as their dense overstory limits growth in the understory. Conversely, disturbance-dependent early and mid-seral aspen stands and mountain-shrub communities provide considerable forage and concealment cover for lactating females and their fawns, and for bucks during antler development. From 1979 to 2015, there was an 88% reduction in annual timber harvest on USFS lands in Idaho, dramatically reducing amounts of beneficial early and mid-seral forest habitats across mule deer summer range. Additionally, fire suppression has been common practice for many decades, and fire-return intervals in conifer forests are now much longer than those prior to advanced fire suppression activities. Reductions in timber harvest and longer fire-return intervals result in maturing conifer forests across Idaho. Not only are older forests less productive for mule deer and other early successional species, but they are more prone to stand-replacing fires rather than historical mixed severity fires. Further, maturing conifer forests put highly productive aspen communities at risk, as conifers encroach and out-compete aspen stands and prevent regeneration.

Rainfall, topography, soil types, and ecological region also affect productivity on summer range. For example, females with access to highly productive habitats in southeast Idaho select for bitterbrush and wild geranium. Conversely, females in more arid regions of central Idaho, where forage quality is lower, rely heavily on sagebrush to maximize fitness. This finding highlights the value of sagebrush for mule deer in arid portions of Idaho. However, deer with access to higher-quality forage exhibit better body condition and higher twinning rates, and produce fawns 20 Idaho Department of Fish & Game Idaho Mule Deer Management Plan 2020–2025 with higher survival and better growth potential. Furthermore, male fawns born to females in poor condition experience diminished growth potential, which helps explain differences in body size and potential for antler growth among regions in Idaho.

Much of mule deer summer range is protected from rural residential development via federal ownership. However, in Caribou and Bear Lake counties, phosphate mining occurs across a large landscape, primarily on federal lands. Forest and shrub habitats disturbed during mining activities are primarily reclaimed into grassland habitats, permanently removing important shrub and forest habitats from mule deer summer range. Also, important summer range continues to see increases in rural and exurban development on private lands in places such as Wood River Valley (Blaine County) and McCall.  Forested lands, especially those adjacent to population centers, are subject to increased recreational activity (e.g., trail riding, hiking) that may increase disturbance on summer range. Additionally, increased human activity also increases spread of invasive and noxious weeds as people or their pets, livestock, or equipment carry weed seeds to new areas. Canada thistle, leafy spurge, spotted knapweed, houndstongue, and many other weeds can outcompete beneficial native plant species, ultimately reducing amounts of quality forage on summer ranges.

WINTER RANGE

Migratory mule deer accumulate energy in the form of fat reserves on summer and transition ranges and migrate to lower-elevation winter ranges with less snow to conserve energy and minimize fat loss. Winter survival depends on an energy conservation strategy where mule deer use winter-range habitats at lower elevations and on south-facing slopes with adequate thermal or canopy cover. However, vegetative quality and quantity, topography, and weather conditions vary widely on Idaho’s winter ranges, and contribute to differences in habitat use patterns and behavior among wintering populations. These discrepancies among winter ranges are important considerations for understanding habitat requirements of mule deer, and ultimately, how winter ranges should be managed.

Most winter range in Idaho is located on sagebrush-steppe habitat across lands managed by the Bureau of Land Management (BLM) and private landowners. These communities, comprised of sagebrush, bitterbrush, mountain mahogany, juniper, grasses, and native forbs, provide critical food resources during winter. Healthy sagebrush-steppe ecosystems generally occur in lower precipitation zones and are slower to recover from disturbance than higher elevation summer ranges. Mountain and Wyoming  big sagebrush may take 70–300 years to recover after fire events. Hence, winter ranges across Idaho are extremely susceptible to negative effects from increased wildfire frequency, wildfire severity, prevalence of invasive and noxious weeds, and human development.

Historically, fire-return intervals in Idaho’s shrubsteppe averaged 60–110 years and fires were generally small and patchy. More recent fire-return intervals have shortened to 10–25 years, with some areas in southern Idaho burning 7 times over a 32-year period. Additionally, fires have generally become larger, less patchy, and more intense. Reductions in fire-return intervals are perpetuated by invasion of newly burned sites by invasive plants such as cheatgrass, medusahead, jointed goatgrass, ventenata, and rush skeletonweed. These plants provide a fine fuel source that ignites easily and burns rapidly. Beyond creating an environment that is more prone to wildfire, these plants have limited forage value and directly compete with beneficial native plants for limited soil moisture, ultimately reducing the quality of mule deer winter range.

Much of Idaho’s historical winter range has been lost or severely compromised by human Idaho Department of Fish & Game. Expansion of housing development in Idaho, 1970–2010, as adapted from National Park Service. The “New Housing Development” class includes areas that were undeveloped in 1970 and were developed into low-, medium-, or high-density housing by 2010. The “Expanded Housing Development” class includes areas that were low-density housing in 1970 and were developed into medium- or high-density housing by 2010. 22 Idaho Department of Fish & Game Idaho Mule Deer Management Plan 2020–2025 Figure 3. Number of fires (>1,000 acres) that overlapped a specific location, Idaho, 1984–2016. Idaho Department of Fish & Game 23 Habitat development. Additional winter range exists on other private lands that are currently unprotected from direct and indirect threats. Idaho’s human population more than doubled from 1970 to 2010. Since 2010, the population has increased nearly 1% every year, making Idaho the fastest growing state in the nation. During the same time period, rural (42%), exurban (373%), suburban (187%), and urban (612%) development all increased, resulting in a 32% loss of undeveloped private lands. Areas of particular concern for residential development on winter range include the Treasure Valley and much of eastern Idaho. Urban sprawl in prime winter range will continue to directly affect the long-term sustainability of mule deer in Idaho. Indirect effects of development are also of concern. Increased human activity in and around winter range can result in far greater energy expenditure during disturbance events than on summer range, thereby reducing overwinter survival. Increased mule deer densities and poor body condition during winter exacerbate effects of small disturbances, which may lead to reduced survival and lower herd productivity.

MIGRATORY HABITAT

Migration and movement pathways provide crucial seasonal habitats that link summer and winter ranges. Migration allows mule deer to avoid deep snow and other harsh conditions during winter and take advantage of high-quality forage during summer. These migratory pathways concentrate mule deer and increase their vulnerability to human development and other threats, such as direct mortality from vehicles.

As the western U. S. becomes more heavily populated, the focus on protecting and managing migratory pathways has increased. In 2018 the Secretary of the U. S. Department of Interior (DOI) signed Secretarial Order 3362, directing DOI staff to focus efforts on identification and protection of these migratory pathways in coordination with state wildlife management agencies. As an extension of this effort, IDFG is currently analyzing information from radio-collared mule deer to refine our knowledge of migratory pathways across the state.

Timing, speed, and distance of migration between summer and winter ranges varies greatly by location and individual. Mule deer migrations may take 150 miles. Protecting migratory habitat is essential if mule deer are to persist on the landscape. Also important to mule deer fitness and productivity is forage quality along these pathways. Though mule deer could easily complete long migrations in a few days, they instead take weeks or longer to complete their migrations, utilizing forage resources along the way. Mule deer may avoid human development and human disturbances along migratory pathways, which reduces their ability to maximize nutritional intake during migration.Housing development, highway construction and expansion, fences, wildfires, and energy development negatively affect these high-value, long-distance migration corridors. Identifying limiting factors to each migratory pathway and focusing on solutions to protect and improve movement along migration pathways will be a priority during implementation of this Deer Management Plan.

Whitetail Deer

Habitat White-tailed deer are highly adaptable generalists which utilize diverse habitats across the landscape. Nevertheless, because of seasonal changes in weather, forage availability, and nutritional demands, white-tailed deer require a different mix of habitat components at different times of year.

Habitat use is determined by energetic demands of deer throughout the seasons. These demands consist of recovering body condition and supporting fawn development from spring to autumn, and minimizing energy loss over winter when caloric demand often exceeds available forage resources. In spring, deer utilize lower elevation burned areas, riparian habitats, clear cuts, south- and west-facing slopes with open canopies, and agricultural areas to recover lost condition and replenish energy reserves. In summer, deer may follow green-up to higher elevations, while continuing to make extensive use of clear-cut edges, burns, and open forest areas. Deer may also remain in low-elevation habitats that provide adequate combinations of browse and cover throughout the year.

Although availability and quality of winter range are often considered a critical population “bottleneck” (because most mortality occurs in winter), adequate accumulation of energy reserves during summer is at least as critical as winter range availability and quality. Condition of deer entering winter strongly influences their ability to survive. Further, quality of summer range is linked to productivity, recruitment, and growth rates in deer.

Characteristics of ideal winter range vary somewhat with winter severity. At more northern latitudes, white-tailed deer generally remain below 3,000 feet in dense conifer stands, which provide superior shelter qualities during harsh winters. White-tailed deer in southern Idaho typically frequent thickly vegetated riparian areas and productive cottonwood galleries along river corridors year-round. Although some populations of mule deer in southern Idaho make long seasonal migrations from summer to winter habitat, white-tailed deer more often make smaller movements along an elevation gradient.

Maintaining a patchwork of habitats at local scales is critical to retaining productive whitetailed deer populations. White-tailed deer need a mix of different habitat components, such as areas of high-quality forage during summer and forest cover during winter. Having a mosaic of habitat components on the landscape is often dependent on and maintained by different types of disturbance. Before European settlement in Idaho, natural processes shaped the landscape. Today, human activities largely control types and distributions of habitat through activities such as timber harvest, fire suppression, prescribed fires, land-use conversion, etc. Even though some of these activities have potential to mimic natural disturbances and are important in maintaining productive white-tailed deer habitat, balancing production of different habitat components is essential. Appropriate balance can be achieved by selectively influencing ecological succession with fire and timber management, limiting White-tailed Doe CCBY IDFG Idaho Department of Fish & Game 13 White-tailed Deer Management impacts of invasive species, and promoting wildlife needs during planning for land management and development projects.

Ecological succession is the process of changes in species composition, vegetation structure, and maturation of a plant community over time. Consideration of succession is critical because the ability of a landscape to support white-tailed deer dramatically varies with changes in habitat. Typically, most forage in late-successional or climax forest systems is out of reach for terrestrial herbivores or dominated by shade-tolerant understory plants with low nutritional value. Nevertheless, mature forests are an important component in a habitat mosaic with early to mid-seral stands as they provide critical cover during winter. Early seral habitats benefit many wildlife species, including white-tailed deer, because overall plant diversity and forage quality is generally greater. Maintaining a patchwork of mature and early-seral stands provides a diversity of travel routes, screening and security cover, and browse. As such, disturbance sufficient to periodically reset succession is essential to maintaining high-quality white-tailed deer habitat. However, natural disturbance and successional processes are altered on industrial timber lands subject to post-harvest herbicide applications. This practice, employed to reduce competition between broad-leafed shrubs and newly planted or naturally regenerated conifer seedlings, can temporarily eliminate or reduce early seral stages that benefit white-tailed deer.

Wildfire is a natural disturbance mechanism that drives succession and composition of plant communities. Succession of vegetation after fires typically provides a period of excellent forage and cover availability for deer. Current wildfire frequency and intensity have departed significantly from historical regimes throughout many forest communities occupied by whitetailed deer. Intense and severe wildfires, driven by abnormally heavy fuel loads (caused by decades of fire suppression), result in vast areas that recover slowly and remain unusable to deer for long periods of time.

Similar to wildfire, sustainable timber management practices can benefit white-tailed deer by creating a landscape-level mosaic of seral stages through distribution of harvest over time. Timber harvest can simulate natural disturbance regimes when conducted at appropriate spatial scales and harvest intervals. However, conflicts can arise when forests are managed such that landscapes trend away from natural ranges of variability with respect to stand age structure, patch size, and species composition. These forests are often highly fragmented by high road densities, which increase white-tailed deer vulnerability due to increased human activity. Furthermore, increased road densities result in spread of invasive plants, some of which negatively affect habitat quality for native species.

During the public comment period, some constituents expressed concerns that timber harvest on industrial forests has significantly increased in recent years, negatively impacting habitat and deer abundance. To address this concern, IDFG reviewed long-term timber harvest data for private, state, and federal lands in Idaho. At the statewide scale, timber harvest on private lands changed relatively little over the last 50–70 years Timber harvest. Timber harvest by ownership, Idaho, 1950–2018 Harvest in 2018 estimated based on first 3 quarters. 14 Idaho Department of Fish & Game Idaho White-tailed Deer Management Plan 2020–2025 on state lands increased somewhat, but state-managed land comprises a small proportion of forested habitat. The largest change has been a decline in timber harvest from federal lands since the mid-1990s, which strongly contributed to overall reductions in harvest. The Department recognizes timber harvest can be intensive at a local scale (e.g., within a stream basin), resulting in dramatic habitat changes at that scale, and potentially affecting deer numbers in localized areas. At the same time, most forest practices result in stimulation of forage growth and other beneficial habitat features, and in a mosaic of habitat types. Habitat changes brought about by sustainable forestry generally benefit whitetailed deer at the landscape scale. White-tailed deer are habitat generalists well suited to, and somewhat dependent on, periodic habitat disturbances which re-initiate forest succession. Habitat changes associated with timber harvest typically provide high-quality deer habitat within 5–10 years.