D.E.E.R. Project

Oct 09, 2016

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D.E.E.R. Project

By Matthew Hayes

Mule deer have a complex history throughout the western United States. In the days of the early settlers and pioneers, mule deer were relatively scarce; many trappers and explorers reported only occasional sightings of mule deer whereas other big game species were regularly observed. At the beginning of the 20^th century, mule deer populations had been drastically reduced in number due largely to overharvest, market hunting, and overgrazing. Protections were put in place in the early to mid-1900s, eventually leading to ideas such as the North American Model of Wildlife Conservation, which was followed by a dramatic increase in mule deer populations. Mule deer populations peaked between the 1940s to the early 1960s throughout the western US.

Fast forward a few decades to the present day. With a lens to examine population fluctuations over the past 40+ years, a clear pattern has emerged. Populations, at least in Wyoming, appear to go through cyclical periods of increase followed by sharp declines. In reviewing literature and historical documents, concerns about mule deer populations tend to follow huge decreases in populations and when they subsequently rise, research and management become less important. Another point that seems clear in Wyoming is that although we have this see-saw in population numbers, there is a general declining trend since at least the 1970s. On average, Wyoming has seen a roughly 20% reduction in mule deer populations.

The population swings, and general decline, of mule deer since the 1970s has been difficult to understand. A variety of factors have been proposed to explain these declines, including: overharvest, harsh winters, habitat, drought, predation, disease and burgeoning elk populations. Managers have long noted that many areas that mule deer inhabit face different pressures and that populations are likely being driven by a variety of factors. All factors are not influencing populations in each portion of their range. This complication has meant that gaining a more complete understanding of reasons for fluctuations or stagnant growth in population numbers has been elusive. Without a solid understanding of the why and how associated with population fluctuations, it is incredibly difficult for targeted management to be beneficial.

Researchers and managers have made great strides to better understand mule deer ecology and factors relating to their survival and reproduction. In the early 2000’s Global Positioning Systems (GPS) became small enough to fit onto a collar sized for ungulates. Since then, studies have been conducted examining migration and use of the landscape in summer and winter. The effects of drought and shifting precipitation regimes have been investigated as well as determining when, where and how animals are dying. Wyoming has been at the forefront of this research and has helped to better understand the ecology and management of mule deer. A key ecological process that has remained poorly understood are the interactions between mule deer and elk (though some work has been done at the Starkey Experimental Forest).

Mule Deer with GPS tracking collar.

Both mule deer and elk are highly cherished big game species. Wyoming and her residents rely on these animals for hunting, tourism and as a part of our cultural heritage. Nevertheless, at the same time those mule deer populations have generally declined, elk populations have increased dramatically across the same geographical range. Managers and researchers have long wondered if mule deer and elk could be competing for space and resources but, until recently, the ability to study these interactions was almost impossible. Potential for interactions between these 2, highly valued species to affect one another’s abundance has been a bit of a conundrum for decades, probably given the challenges associated with addressing such a complex question. The Deer-Elk Ecology Research Project (DEER) was ultimately incepted out the need to unravel the head-scratching complexities of poor performing mule deer populations, while a similar big game animal continues to grow in the same country.

Population sizes for Deer

Population sizes for Elk

The DEER Project, located in the Greater Little Mountain Area of southwestern Wyoming, aims to increase our understanding of both mule deer and elk. This project is examining parturition timing and location of mule deer, mortality and recruitment of fawns, nutritional condition of adult female mule deer, summer diet overlap between elk and mule deer, space use, recruitment of male mule deer, survival, migration, and dispersal. We also are implicitly examining winter severity, habitat use, precipitation patterns, predation and disease. One of the greatest strengths of this work is the rigorous monitoring of both mule deer and elk in the same system. Many studies prior have examined one species or the other with inference to supposed interactions, but the DEER project will be able to analyze these interactions at a much finer scale. Another added benefit of this project is that it occurs in a high-desert system—an ecosystem ubiquitous throughout Wyoming but less studied compared to high-elevation systems. Far from being a one-off or unique system, the results from this work will be applicable to mule deer and elk throughout their shared range.

Future articles will focus on updates from the DEER project. You can follow along with the project, donate and subscribe for updates at www.deerproject.org.

The Western Association of Fish and Wildlife Agencies (WAFWA) has explored the issue of mule deer decline in depth and has published a very approachable book on the topic; you can check out the website at www.wafwa.org and navigate to the Mule Deer Working Group for more information.