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Winter 2016/2017 Survival

The winter of 2016/2017 was abnormally severe in the western portion of Wyoming. Record snowfalls, cold temperatures, and persistent stretches of inclement weather combined to negatively affect animals on winter ranges.  The Greater Little Mountain Area (GLMA) was not entirely spared by this weather pattern, though the severity south of Rock Springs ebbed and flowed as the winter progressed. In late January-early February, a brief warm period with little precipitation provided a reprieve for animals on winter range. This brief period likely helped animals cope with the remainder of winter.

Although winter was not quite as severe south of Rock Springs, a number of animals were lost because of winter conditions or a combination of winter conditions and predation. Several animals were lost around Christmas to predation by mountain lions and several were lost towards the end of winter to apparent malnutrition-related causes.  Adult mortalities over winter in the Wyoming Range were almost double that experienced by the south Rock Springs herd, of which most was malnutrition-related.

Fawn mortality in 2016 for the south Rock Springs herd was nearly 75% by November, which left 10 remaining fawns to survive the winter months. By April, 5 of the remaining fawns from the summer were still alive, amounting to roughly 91% fawn mortality from the summer of 2016 through spring 2017.


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November 2016 Captures

Fall 2016 captures occurred the first week of November, where we deployed or recaptured 53 collars on adult female mule deer, and 35 collars on adult female elk. We also captured and collared 15 adult mule deer bucks to better understand their habitat use and movement during different times of the year.

During fall capture events, we assess body condition using ultrasonography and a palpation score. Ultrasonography is used to assess the amount of fat reserves and thickness of various muscles. A combination of ultrasound and body palpation scoring allows us to estimate the percent body fat of individuals and to evaluate how much fat they accumulated on summer range.




Mule Deer Bucks

The GLMA is a popular destination for mule deer hunters, but despite its popularity, evidence from Wyoming Game and Fish surveys suggest that buck:doe ratios have decreased in the past decade. Additionally, anecdotal evidence from locals suggest that mule deer bucks are harder to find during hunting season than previous years. This spurred increased interest in determining what is happening with mule deer bucks in this population and adds to the ongoing work of the DEER Project. So, during the November 2016 helicopter captures of the DEER Project, we kicked off the buck portion of our work. We captured and collared 15 mule deer bucks between 1 and 5 years old, and plan to collar an additional 25 new bucks each year of the project.

While we don’t know what is happening with the male segment of the population, our capturing and collaring efforts will yield significant evidence as to what might be going on. One possible explanation for the apparent lack of males observed in this system could be either dispersal movements or early migrations to neighboring areas or states just prior to hunting seasons. As we obtain more data and increase our sample size, we’ll be able to better understand the recruitment and movement of the male segment of the population. Stay tuned for more information as it becomes available!




Summer 2016 Fawn Season Recap

We captured 55 fawns from 36 adult deer (~70% of the pregnant deer). Of the 55 fawns captured, 32 were females and 23 were males. Between the date of parturition and the end of our intensive monitoring period in August 2016, we observed 30 mortalities (54% loss). 15 of those fawn loses were due to predation events including: coyotes, feline, and one bear-related mortality. Several other fawns died from malnutrition or disease with a few accidental mortalities, 1 stillborn and 4 unknown. Unknown mortalities occur when there is not enough of the fawn remaining to make a confident decision on cause of death.

We could not ascertain cause of death of several fawn mortalities, so we sent them to the Wyoming State Veterinary Lab (WSVL) for necropsies. So far, necropsy results suggest that a single fawn was infested with an exotic louse, which may have contributed to its death, but the ultimate cause of death is unknown. Additionally, several fawns that were killed by predators also tested positive for adenovirus in bone marrow. Therefore, it is possible that infection of adenovirus may have predisposed these animals to mortality from predation, a scenario similar to what we have observed in the Wyoming Range as well.

Fawn monitoring was lessened between the end of August and November 2016 captures because the frequency of fawn mortality is typically concentrated near birth. By November captures, 15 of the 30 fawns from Augusts were still alive, meaning we received a pulse of mortality in autumn where 15 fawns died during September and October. Overall, 73% of fawns had died by November captures. It is still unclear as to why the 2016 season produced such a high mortality rate, but we will continue to monitor these patterns in the 2017 and 2018 field seasons, and as this project continues, we will be able to disentangle important roles of predation, nutrition, and disease on fawn survival.

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Mule Deer and Elk Population Sizes

Mule deer have had a complex history throughout the western United States. In the days of the early settlers and pioneers, mule deer were a relatively rare species. At the beginning of the 20th century mule deer numbers were drastically reduced in number due to overharvest, market hunting, and overgrazing. Protections were placed on mule deer causing numbers to drastically increase and peak between 1940s and 1960s throughout the western US.

Present day, with a lens to examine population fluctuations over the past 40+ years, a clear pattern has emerged. Populations in Wyoming appear to go through a cycle of increase followed by sharp declines. In Wyoming, although we observe this see-saw in population numbers, there is a general declining trend in population numbers since at least the 1970s; on average, Wyoming has seen a roughly 20% reduction in population numbers across the state.  The population swings and general decline has been difficult to understand; a variety of factors have been proposed including: overharvest, harsh winters, habitat, drought, predation, and disease. A question has been raised as to why there are viable and growing elk populations while mule deer in the same systems continue to struggle. Questions arise regarding potential competition between mule deer and elk, or the conditions that have fostered growth of elk while being detrimental for deer

The complexity of these questions and the difficulty in answering them has meant that gaining a more complete understanding of the reasons for fluctuations or stagnant growth in populations has been elusive.  Without a solid understanding of the why and how associated with population fluctuations, it is incredibly difficult for targeted management to achieve desired outcomes.





Summer 2016 Project Update

We have been busy conducting field work south of Rock Springs in support of the DEER Project. As fawn captures have wrapped up, we are turning our attention to monitoring for any mortalities and collecting fecal samples. Determining causes of mortalities will help us understand the important causes of mortality while collecting fecal samples will allow us to determine the extent that mule deer and elk diets overlap.

We’ve put together a full report on all of our activities so far this year (click on the link below).


Thank you all for your continued support!







Deer/Elk moving to summer ranges

As we prepare to get out and capture fawns, just wanted to leave a quick update on where animals are and what is going on.

We finished helicopter capture efforts in late April. This brings our sample size up to 51 female mule deer and 35 female elk. Shortly after captures, animals appeared to begin migrating or possibly complete migration. The reason that we are capturing so late, we typically like to capture in March, is due to somewhat abnormal migration patterns witnessed by locals for this population. We know that some animals begin fall migration in September but spring migration was a bit unknown. It is possible that some of the animals we caught spend most of the winter in neighboring states but summer in Wyoming.

All that aside, animals appear to be on summer ranges or, in some cases, as close as they can currently get with some snow on higher peaks. The maps below show mule deer and elk densities across the study area. Black lines are roads and white names are approximate labels of geographical features. Darker colors indicate higher densities.

Stay tuned for some updates once fawn captures begin!




Deer/Elk Locations

We’ve been keeping an eye on where the deer and elk have been moving this winter. Even though we captured the first week of November, it appears that we caught all resident animals. We had hoped to capture early enough that we’d get animals collared before migration started in the fall. Our game and fish colleagues informed us that animals appeared to have taken off but we ended up getting some collars out in November anyways. We saved quite a few collars to try and grab migrants this coming spring.


Here are a few maps to give you a sense of where deer and elk are on the landscape thus far. Red areas are areas of higher likelihood of having an animal. The first map are deer while the second map are elk.

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Preliminary Data

Time seems to be in short supply but there are a few interesting tidbits that have come out of the capture data.

As some may know, we have quite a few research projects ongoing throughout the state which means we are able to compare data collected in the Greater Little Mountain Area with other areas around the state. This helps us to understand not only the area south of Rock Springs but helps to inform researchers and managers for how populations compare with each other. These comparisons give an indication for relative differences amongst different populations and what is limiting to populations in different areas.

One interesting find thus far has been the size and condition of mule deer caught in the Greater Little Mountain Area (GLMA) compared with deer captured in the Wyoming Range. It shouldn’t be too much of a secret that the Wyoming Range has some pretty stellar summer range compared with the GLMA. Even so, initial results suggest that mule deer in the GLMA are roughly 12% lighter than deer captured in the Wyoming Range at a similar time of year. Not only did the deer weigh less, they were physically smaller as well. Generally speaking, deer in the GLMA were also in poorer shape going into winter than deer that summered in the Wyoming Range.

It is entirely possible this is due to having many more samples in the Wyoming Range (several years of captures) compared with just a few captures so far in the GLMA. We’ll have to keep an eye and see if this pattern holds.

DEER = mule deer in the Greater Little Mountain Area

WR = mule deer in the Wyoming Range




DEER Project Initial Captures

Following several years of discussions, prep work, meeting with local stakeholders, wildlife officials and university researchers, the DEER Project officially kicked off in early November 2015.

Deer populations have been declining range-wide. Coincident with these declines are general increases in elk populations, more frequent drought and fluctuating predator populations. Recent work in the nearby Wyoming Range also hints at the possibility that disease could be playing a role in deer populations, possibly even more so than predation. These changes are set on a backdrop of fluctuating temperature and precipitation regimes, including more frequent and more severe drought.

In few places are these questions more prevalent than for the south Rock Springs mule deer and elk herds in southwest Wyoming (mule deer: Herd Unit MD424, HA101 and HA102; elk: Herd Unit EL424, HA30, HA31, and HA32).  This region harbors some of the most sought after mule deer and elk hunting in the state of Wyoming.  While elk have been above desired levels during most of the last 2 decades, the mule deer population remains about half of the desired population level. In an effort to address the underlying reasons for failed growth of this and other mule deer populations in the West, a non-profit organization (Muley Fanatic Foundation), a management agency (Wyoming Game and Fish Department), and a research entity (Wyoming Cooperative Fish and Wildlife Research Unit) have formed a key partnership to conceive and execute the Deer-Elk Ecology Research (DEER) Project. The goal of the project is to identify the factors regulating growth and distribution of mule deer in this high-desert ecosystem, while simultaneously developing a better understanding of the ecology of elk and their interactions with mule deer. The DEER Project will take a novel and integrative approach to investigate key questions that continue to be a concern for mule deer populations including, effects of harvest, habitat condition, drought, predation, and competition with elk. The DEER Project will be the first of its kind to explore all of these key factors in tandem, and will be done so through a unique partnership that unites hunters, conservationists, managers, and researchers to the benefit of the Icon of the West.


Special thanks to all the MFF volunteers that helped make our first round of captures a success. Also thanks to Lucy Wold for her picture taking expertise and capturing our better side!