Chronic Wasting Disease

Recently, however, the disease was detected in mule deer near Alpine and Pinedale, setting off renewed concern about the impact of CWD on feed ground elk. These feed grounds facilitate dense aggregations of elk during the feeding season, and it is these high elk densities that may put feed ground elk at greater risk of CWD spread and subsequent declines in survival and population growth. Studies show that CWD prevalence tends to be higher in mule deer than elk and Wyoming surveillance data suggest that CWD in mule deer is more widely distributed across the state. As a result, introduction of CWD into the feed ground system is likely to come from interaction with infected mule deer or the environment contaminated by infected mule deer.

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Current Projects

1. Modeling the role of predation in CWD dynamics.

The combined effects of wolves and cougars on CWD in the Rocky Mountain West will not be empirically estimable for decades given that CWD is slow to develop, and only recently did the CWD distribution begin to overlap with areas containing suites of predators. Additionally, managers lack timely indicators of CWD presence in host populations. We currently rely on the non-invasive sampling of wolf-killed, cougar-killed, and road-killed cervids, as well as harvested elk and deer to monitor for CWD in Yellowstone and Grand Teton National Parks and Wyoming. This method of collection produces small sample sizes and needs to be supplemented with wider geographic sampling and alternative approaches. We propose to simulate the potential role of different predators and identify key indicators of CWD invasion in elk and deer in the Greater Yellowstone.

Contacts: Paul Cross, USGS; Nathan Galloway, NPS; Ellen Brandell, Penn State University

2. Modeling alternative hunting strategies on CWD, deer and elk dynamics.

Male deer and elk are often found to have higher prevalence of CWD than females.  There are multiple mechanisms that may drive this observed pattern. Female to transmission to males may be high due to male mating behaviors. In this case, males are being exposed at higher rates resulting in higher prevalence, but are not necessarily the most responsible for transmission.  This has potential management implications for the efficacy of male-biased harvest. In this project we explore the consequences of different harvest management regimes under different transmission scenarios between male and female deer using age-structured disease models.

Contacts: Paul Cross, USGS; Will Rogers, Montana State University

3. Assessing the role of artificial mineral licks in CWD dynamics

Management strategies to control and slow the spread of CWD into non-endemic areas rely in part on limiting higher prevalence “hotspots” which may center around limited resources that increase wildlife host densities. Agricultural mineral tubs and salt licks have been observed to be visited by deer and other cervids and may serve as a fomite for CWD transmission. This can occur by animals successively visiting and licking a tub or block or licking the salt that leaches into the ground around these sites. Elemental additives to salt such as copper and manganese may have the added effect of increasing the longevity and transmission potential of CWD prions (Nichols et al, 2016). Our goal is to determine how important anthropogenic mineral licks are to the transmission of CWD.

Contacts: Paul Cross, USGS; Brant Schumaker & Bevin McCormick, UofWy

4. Estimating the effects of artificial feeding at the National Elk Refuge on elk contact rates.

In November 2018 chronic wasting disease (CWD) was detected for the first time in Teton County, Wyoming, in the heart of the globally-significant Greater Yellowstone Ecosystem (GYE). The detection occurred in a mule deer in Grand Teton National Park (GRTE) near the northern boundary of the National Elk Refuge (NER). Elk that winter on the NER are managed under the USFWS Bison and Elk Management Plan, in collaboration with the Wyoming Game & Fish Department (WYGFD). NER elk densities greatly exceed levels predicted to result in rapid population declines with the introduction of CWD. NER management options that influence animal aggregation and distribution include feeding and hunting.  We are quantifying elk contact patterns on the NER and the role of supplemental feeding in modifying potential CWD transmission. We are also developing methods to more cost-effectively estimate elk densities using tools including satellite imagery and unmanned aerial systems and to evaluate the success of adaptive management in changing densities and degree of concentrations of elk.

Primary Contacts: Tabitha Graves, USGS; Eric Cole, USFWS

Past work:

Our past work on CWD focused on modeling efforts to understand how a persistent environmental reservoir may affect long-term disease dynamics and population dynamics of deer and elk. In addition, we worked on assessing mule deer connectivity around Montana by contributing to collaring efforts as well as using genetic methods.