The Decline of Deer Populations

Deer populations in the western United States and several states along the east coast are in decline (see supporting the articles at right). One issue is forest management, mature forests produce much less food and habitat for deer than dynamic forests (see this article, Deer-Friendly Forests). Also, as their habitats and the climate changes, development without regard to wildlife makes it harder for the deer to move about, segmenting the herds into groups that are too small to be sustained. Some hunters say that the expanding mountain lion population is a primary cause. This deer friendly project is an effort to provide information that can be used to improve decision making with regard to the ecology represented by deer.

Some of the states with declining deer populations are conducting studies for the cause of the decline, see the list below along with the suspected cause for the decline.  Many states along the east coast suspect the rise of a new coyote hybrid - larger coyotes that have interbreed with wolves -  are responsible for the new, downward trend in deer populations.  [double click to enlarge the image[


Discover the Mule Deer, Issues Contributing to the Decline of Population, Wyoming - June 15, 2012

Where have all the Oregon deer gone? November 15, 2012 Portland Tribune
... Deer populations are struggling across the state, says Don Whittaker, an ODFW game biologist. That’s true for black-tailed deer and mule deer, both native to Oregon.  
Black-tailed deer numbers are hard to track because of their reclusive nature and thick forested habitats... The problem may partly stem from the series of four large forest fires, starting in the 1930s, known as the Tillamook Burn, which consumed 550 square miles of timber in Northwest Oregon... Reforestation of the burned land .... And as charred lands came back to life, trees began to shade out the deers’ favorite shrubs...

Deer Ecology
Current estimates of deer populations support other important wildlife management tools such as corridor maps. Recently, Congressman Ira Ruskin of California introduced a bill to create wildlife corridor maps (see video), a critical tool for environmental management in a era of significant geospatial development. De Anza college has taken a lead in this effort with their Wildlife Corridor Project, focused on the Coyote Valley south of San Jose. A statewide effort supported by the California Department of Transportation provides this website for updates on their collaboration with California Fish and Game. Local data is helpful in the success of these efforts.

California Wildlife Corridor Bill, Ira Ruskin

In April, 2010, the California Essential Habitat Project Map was released providing the corridor map below with essential corridors identified by cost. Additional corridor research for California can be found at

One of the oldest social networks in the Americas, the Southern Ute Indian tribe has created a deer corridor map for Southwest Colorado to assist in environmental decision-making with regard to development of the HD mountains related to oil and gas development. The corridor map below comes from the Vermont Department of Fish and Game's corridor project.

Example of a Deer Corridor Map from a study at Colorado State University

PowerPoint Slides Describing Oregon's Wildlife Connectivity Strategy 

Extinction Probabilities for Birds and Sheep When Populations Decline 

The Wildlife Corridors Map along the Idaho and Montana borders developed by the National Fish and Wildlife Foundation

The California Deer Decline and Possibilities for Restoration Cal-Nevada Wildlife Transactions, 1976

Seasonal neighbors: residential development encroaches on mule deer winter range in central Oregon March 27, 2012 Oregon, U.S. Forest Service Pacific Northwest Research Station, Marie Oliver
Mule deer populations in central Oregon are in decline, largely because of habitat loss. Several factors are likely contributors. Encroaching juniper and invasive cheatgrass are replacing deer forage with high nutritional value, such as bitterbrush and sagebrush. Fire suppression and reduced timber harvests mean fewer acres of early successional forest, which also offer forage opportunities. Human development, including homes and roads, is another factor. It is this one that scientists with the Pacific Northwest Research Station and their collaborators investigated in a recent study. As part of an interagency assessment of the ecological effects of resort development near Bend, Oregon, researchers examined recent and potential development rates and patterns and evaluated their impact on mule deer winter range. They found that residential development in central Oregon is upsetting traditional migratory patterns, reducing available habitat, and possibly increasing stress for mule deer. Many herds of mule deer spend the summer in the Cascade Range and move to lower elevations during the winter. An increasing number of buildings, vehicle traffic, fencing, and other obstacles that accompany human land use are making it difficult for mule deer to access and use their winter habitat. The study provides valuable information for civic leaders, land use planners, and land managers to use in weighing the ecological impact of various land use decisions in central Oregon.

Proceedings of the 9th Western States and Provinces Deer & Elk Workshop, 2011 (Describes a number of recent studies related to decline of deer populations)
Effect Of Enhanced Nutrition On Mule Deer Population Rate Of
Change:  We found strong evidence that enhanced nutrition of deer reduced coyote and mountain lion predation rates of less than 6 month old fawns and adult females.  Winter range habitat quality was a limiting factor ... we recommend evaluating habitat treatments for deer that are designed to set-back succession and increase productivity of late-seral pinyon-juniper habitats that presently dominate the winter range....
Utilizing Antler Point Restrictions For Mule Deer To Maximize 
Hunter Opportunity In Southern British Columbia:  We provide explanations as to why our results appear to counter some findings from other studies and suggest that utilizing a combination of 4-point and any-buck seasons for mule deer for 92 days can maintain maximum hunter opportunity while retaining a sustainable harvest.
Wildlife habitat patterns changing November 17, 2012 California, San Francisco Chronicle
.... Best estimates say the number of deer in California has plummeted from 2 million in the 1960s to about 450,000 (of which most are "suburban deer"). Expanded highways and new subdivisions have blocked historic migration routes. Timber companies cut down forests and replanted them with conifers, which deer can't eat, so there's less food. Record-high populations of mountain lions eat a deer or two per week... the big herds were devastated...

Deer management decision making time, decline of deer January 13, 2013 West Virginia, The Logan Banner
... Deer kill numbers are rolling in at roughly half what they were a short decade back...  Habitat quality and environmental factors from the likes of predators and disease to mast failure and winter severity all have and play important roles... Logging had all but ceased during the Great Recession and habitat thus suffered. Mast failures were woven in with a return of winter, tag teaming on occasion for major winter kills. EHD disease ... CWD ...

Gerry Lavigne, who served as Maine's state deer biologist for 30 years, talks about areas with deer habitat, but no deer. January, 2013

The Mule Deer Wars December 17, 2012 Colorado, Huffington Post
... It began in the 1990s, when state wildlife managers started reporting lower mule deer populations and decreased fawn-to-doe ratios throughout the West....  in 1999 the Colorado and Idaho wildlife departments launched long-term investigations into the true causes of the perceived mule deer decline. Both studies soon enough reported, in line with previous research throughout the West, that coyotes and other predators indeed are capable of keeping isolated and already critically low deer populations from recovering via a rare phenomenon known as a "predator pit." 

The Whitetail Depression September 3, 2011 Outdoor Life... “I think we’re nearing a crisis mode,” says Dr. Woods ... a consulting wildlife biologist ... “The best-case scenario is that deer populations drop 10 to 25 percent over the next couple years.” ... a troubling combination of habitat loss, escalating numbers of predators, underfunded wildlife agencies and even hunters’ behavior ... Woods and others are suggesting whitetail populations are poised to experience a steep drop, somewhere between a significant correction and a catastrophic crash.... [Adams says] “A young hardwood forest can easily produce 1,000 pounds of available food per acre. A mature forest produces 50 to 100 pounds.... [a major risk factor] Among non-hunters, whitetails have an image problem. Over the past two decades, their stature has declined from nobility to nuisance.

Mule deer at a crossroads December 20, 2012 North Dakota, Bismarck Tribune
Mule deer are much more limited in their range in North Dakota compared to other Western states, where they can move to a summer range and winter range to take advantage of the best food sources. Badlands mulies are locked in to one area and as oil exploration, roads and other activities expand, it pushes them farther away from prime habitat... Bruce Stillings, big game biologist for the North Dakota Game and Fish Department, said a five-year study to gauge the impact of the oil boom will begin in late January or early February.

Disappearing Mule Deer A New Reality Throughout Western US January 4, 2013 NPR, Audio Discussion
Scientists throughout the West are trying to figure out the mystery of the disappearing mule deer. Since the 1970s, biologists in Colorado, Wyoming and Utah have seen deer populations drop by 50 percent.  The potential causes vary. Oil and gas development and the growth in coyote populations top the list.

California deer population declines as habitat disappears April 8, 2012 Sacramento Bee, By Matt Weiser 
... since 1990, California has lost nearly half its deer population, according to the state Department of Fish and Game ... mainly for one simple reason: habitat loss... Between 1990 and 2000, according to the U.S. Environmental Protection Agency, 75,000 acres per year were converted to low-density housing across California... The natural sources of this deer food have been largely eliminated by a century of fire suppression in forests – the same problem that has caused forests to become overstocked with small, young trees that now pose an enormous fire risk... [estimated current deer population is 445,000 compared to about 800,000 in the period 1800 to 1850]

Where have all the deer gone? July 1, 2012 California, Napa Valley Register , Bill Bishop, Sr.
Having spent most of my life in Napa County, I am appalled at seeing the rate of disappearance of our wildlife. I worked as a cattleman on the Soscol area land for 30 years and the Soscol deer population, which used to have more than 200 doe in it, has maybe 10 left.... Why is Fish and Game taking money for deer licenses when there isn’t anything left to shoot? Is it too late to do anything? Are we near shooting the last Bambi? 

California Black-tailed Deer, where are they? September 15, 2012, Jeffrey Banke
... As a photographer ... searching for black-tailed deer to photograph became more and more difficult to locate animals this year ... interviewing Sierra Pacific employees who are in the woods logging for months at a time who have seen very few deer confirm this observers own research. It would seem in conclusion, that if we do not have some radical changes in both the wildlife management approach by the DFG ... then we are on a continuing downward spiral... 

California's mule and black-tailed deer are in decline. Historical deer population data.Northeastern California has experienced the sharpest percentage decline in deer, followed by the northeastern Sierra. Deer populations on ...

Decline In Mule Deer Numbers (blog) Mule deer numbers throughout the west are declining in rates that are alarming. Habitat loss is a major factor. 

Mule Deer Management January 2012, Muley Crazy Magazine, by Dr. Jared Teter 
The article proposes reasons for the decline in mule deer numbers.The entire article is attached to this post as a single PDF download (click here), or can be viewed via the links below:

DNRE: Deer count down 9 percent (Michigan) Sault Ste. Marie Evening News MARIE — The official deer harvest numbers from 2009 were down 9 percent from 2008, according to a recently completed report issued by the Michigan ...

[PDF] THE CALIFORNIA DEER DECLINE AND POSSIBILITIES FOR RESTORATION by WM Longhurst - -This paper dealing with the possible factors responsible for the decline of deer populations in California is a progress report and a more detailed and ...

North American Mule Deer Conservation Plan - MULE DEER ... From Alaska, down the Pacific Coast ofCalifornia to southern Baja Mexico and from the extreme ..... decline of mule deer populations over large portions ..

SCIENTISTS, MANAGERS OUTLINE BLACK-TAILED DEER DECLINE - Black-tailed deer, once numerous throughout the woods of western Oregon, are suffering a populationdecline, scientists reported ...

Blacktail deer populations hanging on, but there's reason for concern Oct 9, 2009 ... Blacktail deer populations in Southwest Washington are not in crisis, far from it. ... MOVE SLOWLY: Move as slow as a feeding deer. ...

Spring mule deer survey done‎ Bismarck Tribune - Western North Dakota's mule deer population has decreased slightly for the second consecutive year, based on observations during the North Dakota Game and ... 

Study of the Reasons for the Decline of Nevada's Deer PopulationMULE DEER INITIATIVE Commission Briefing - February 20, 2009, (Oegon). Issue: Researchers and wildlife managers generally concede mule deer achieved maximum abundance during the 1950s and ‘60s. Since then, mule deer have declined across the West, including Oregon. The most recent decline appened during the early 1990s and, though not fully understood, it is believed to be primarily due to the combined effects of drought and severe winters. Historically, deer populations rebounded quickly after such climatic extremes. However, in recent years, production and survival of fawns have remained at depressed levels. Low recruitment, severe winters, dry summers, changing predator/prey relationships, and increased habitat loss have pushed mule deer populations lower than the department and public desire.

From Wildlife.Utah.Gov: "Since 1922, the Western Association of Fish and Wildlife Agencies (WAFWA) has served as a leader promoting management and protection of fish and wildlife in the western United States and Canada. An organization represented by 17 states and four Canadian provinces, WAFWA has faced the difficult challenge of sifting through the ever-changing societal, economic, political and scientific issues that define natural resource management in a West that has undergone many changes. WAFWA is particularly concerned about mule deer, a species that lives in every North American habitat except for the tropics, arctic and extreme deserts. Mule deer numbers and distribution have been declining throughout the West since the latter third of the 20th century. To address this concern, the Mule Deer Working Group was established at the midwinter meeting of WAFWA in 1998. The group was charged with finding “solutions to our common mule deer management problems,” expanding “cooperative research and management in the Western states and provinces,” and sharing information with agency directors and administrators on mule deer issues."

 Example of a Deer Population Collapse



 California Department of Fish and Game Deer Distribution Map

 (click on images for larger view) 

Black-tailed DeerThe history of the black-tailed deer has shown both the positive and negative influences man can have on wildlife. During pre-settlement times, ... 

Sitka Black-tailed Deer: Wildlife Notebook Series - Alaska ...
Apr 1, 2010 ... Sitka black-tailed deer species description for the Alaska Fish and Game Wildlife Notebook ...Life history: Fawns are born in late spring. ..

Tavis Forrester; University of California, Davis; 1075 Academic Surge, One shields Ave, Davis, CA, 95616; 831-233-1827;; Heiko W. Wittmer 
Recent population declines in mule and black-tailed deer (MBTD) (Odocoileus hemionus) have shown the difficulty in predicting ungulate population trends and raised concerns about the role of predation in deer dynamics. We reviewed 56 demographic and predation studies to summarize current knowledge of mechanisms in MBTD dynamics. We found reported MBTD demographic rates match general ungulate patterns, but often data to accurately estimate population growth was missing. Predation was a large proximate cause of mortality, but nutrition effects were also important and it was unclear if predation regulated populations. In light of this review we present preliminary data from an ongoing study of black-tail deer survival in the California coast range. We placed radio ear tags on 86 fawns and GPS collars on 41 adult females and monitored deer daily during summer months and every 10 days in other seasons. The most common proximate cause of mortality was predation for both adults and fawns. Fawn survival to recruitment of 0.21 and adult female annual survival of 0.68 (Kaplan-Meier estimator) were both below average values found in our review, especially adult female survival. The role of habitat quality and nutritional condition in survival is pending further analysis.