American Elk

American Elk once roamed freely throughout most of North America. Due to over-hunting, habitat fragmentation, and other anthropogenic activities the elks’ numbers have declined over the past century. There are still four extant subspecies of American Elk in North America. Elk in North America have adapted well to the changing conditions over the past one hundred years, however in order to conserve this essential species it is helpful to know their ecological needs. Like all biological species there are epidemiological threats to this species, which one will briefly be discussed that is currently threatening this species. Lastly, just as humans are, elk are also impacted by climate change; this will be analyzed with the affect’s climate change has on this magnificent ungulate species.

The below map below shows current and historical elk range in North America.

Historically there were six species of elk roaming the North American Continent; the Eastern Elk and the Merriam’s Elk are both extinct. The extant species include the Manitoban Elk, Rocky Mountain Elk, Tule Elk, and Roosevelt’s Elk. The Eastern Elk (Cervus canadensis canadensis) freely roamed the Northeastern United States. This elk species was declared extinct in 1880 by the U.S. Fish and Wildlife Service (USFWS).

Merriam’s Elk were found in the southwestern United States, experts’ site unregulated hunting and habitat encroachment by cattle farming eliminated this subspecies of elk from the planet in 1906.

Today, Tule Elk (Cervus elaphus nannodes) is the smallest living subspecies of elk, which used to dominate the central and northern valleys of California, are managed by state and federal agencies (NRCS;, 1999).

The Rocky Mountain Elk (Cervus elaphus nelsoni) is an extant subspecies of elk, which is the most plentiful, with the latest census estimating their population to be about 850,000; found in their natural range in the Rocky Mountains of the western United States and reaching across the continent and into some of the eastern states (NRCS;, 1999).

Roosevelt’s Elk (Cervus elaphus roosevelti) is found in the Pacific Northwest and is the largest subspecies of elk. (NRCS;, 1999)

Elk congregate in large open grass fields in order to forage, typically in the early morning and late afternoon, before retreating back to the safety densely wooded areas (NRCS;, 1999). Roosevelt and Rocky Mountain Elk migrate seasonally to mountain forests and meadows and the transitional zone between the open plains (NRCS;, 1999). Tule elk roam the open coast of California foraging and finding pockets of concealment (NRCS;, 1999).

 American Elk forage seasonally on grasses, forbs, and woody plants (NRCS;, 1999). As winter begins to senesce, elk begin to heavily graze on grasses such as; native bluegrasses, rough fescue, Idaho fescue, prairie June grass, needle-grasses, blue bunch, and slender & thick spike wheat grasses. The year progresses into spring and summer, elk rely on forbs and woody vegetation for sustenance (NRCS;, 1999). As the earth begins to tilt away from the sun and temperatures begin to cool, these ungulates again turn their attention to grasses (NRCS;, 1999). Elk are resourceful feeders and consume a wide variety of plant species, their willingness to forage outside of the Poaceae family allows this species to consume the correct mixture of nutrients to survive the winter (NRCS;, 1999)

Elk drink water from springs, lakes, wetland ponds, rivers and streams; vegetation and snow also contribute to elk water intake (NRCS;, 1999).

As the calendar year begins and winter is in full effect in the northern hemisphere, elk can be found in north & northeast facing lower-elevation densely wooded mountain slopes that provide concealment (NRCS;, 1999). Conversely, southerly facing slopes provide food and more favorable environmental conditions during the day (NRCS;, 1999). During the spring and fall transitional months elk migrate between winter and summer ranges (NRCS;, 1999). Transitional ranges are composed of fir, aspen, and pine trees; as well as other woodland shrubs and forbs which enable elk to build fat stores to support offspring in the spring and throughout the fall (NRCS;, 1999). As the earth tilts to absorbs the suns full energy and extreme winter weather begins to wane, elk can be found in higher elevations. Human avoidance is a contributing factor to elk summer range, as well as new grasses, forbs, and woodland cover (NRCS;, 1999). From May to June elk calves are vulnerable to predation, therefore elk seek areas which are free from disturbance of predators, and are close to high quality food (NRCS;, 1999).

Because the elk population has grown for decades in the absence of natural predators, elk have consumed some plant species to the brink of extinction. To counteract the absence of natural elk predators, National Park Service (NPS) Rangers act as elk predators, by limiting elk access to certain flora by fencing and elk hunting programs; these methods simulate fear of and predation by wolves respectively (Hermans, Lee, Dixon, & Hale, 2014). 

One of the biggest epidemiological threats to American Elk species is Chronic Wasting Disease (CWD). CWD is a transmissible spongiform encephalopathy which infects a wide variety of ungulates (Pulford, et al., 2012). Transmissible Spongiform Encephalopathies (TSEs) do occur in other species of animals; scrapie in sheep, Bovine spongiform encephalopathy or mad cow disease in cattle, and rare genetic prion diseases in humans, such as Creutzfeldt-Jokob Disease (CJD) (Moore, et al., 2017). The Prion Protein of Chronic Wasting Disease (PrP-CWD) is an abnormal, pathologic protein which is misfolded and merely needs to encounter the healthy protein PrPc, a normal cell-surface glycoprotein, in order to spread this highly infections neurodegenerative disease (Moore, et al., 2017). This easily transmissible disease is a serious threat to ungulate species, and should be monitored closely. The map below shows how widespread this little known disease actually is.

The current literature on climate change leaves little room for debate about if the climate is changing, but research still needs to be conducted to discover the full array of impacts climate change will have on the globe. In 2000 researchers from Colorado State University did an analysis of the impacts of climate change on elk populations in the Rocky Mountain National Park located in Colorado. The researchers sought to determine the effects of future weather an elk population density. The scientists used the United Kingdom’s Committee on Climate Change (CCC) and Hadley Models to predict the environmental conditions out to 2100. The simulations showed a negative correlation between elk population size and increasing summer mean monthly minimum temperatures (Wang, Thompson Hobbs, Singer, Ojima, & Lubow, 2002). However, the simulation found an increase in summer mean monthly precipitation was positively correlated to elk population size (Wang, Thompson Hobbs, Singer, Ojima, & Lubow, 2002). The model was configured to determine the winter effects on elk population densities as well and found there was a negative correlation between winter precipitation and elk population (Wang, Thompson Hobbs, Singer, Ojima, & Lubow, 2002).

While the CCC and Hadley models agreed that the globe would continue to warm over the next century, they produced disjointed precipitation predictions. The CCC model showed an overall drying trend in the front range of the Rocky Mountains, predicting a decrease in precipitation of over 1.12cm. The Hadley Model forecasted a 5.05cm average increase in precipitation per year over the remainder of the century (Wang, Thompson Hobbs, Singer, Ojima, & Lubow, 2002). The map below is in agreement with the CCC model drying trend, predicting a decrease in precipitation in the Rocky Mountain National Park between the range of 0.0cm to 2.2cm. Furthermore, this map agrees with the assessment of both models of increasing temperatures. This map predicts snowmelt to occur two to three weeks earlier in the year over the next twenty years in the elk's range.

The researchers then predicted based on these simulations that the equilibrium population for the elk herd in the Rocky Mountain National Park is 1,600 under CCC conditions and 2,000 under Hadley conditions (Wang, Thompson Hobbs, Singer, Ojima, & Lubow, 2002). This is a 1.6 to 2.0 increase in the population density of elk under the predicted environmental conditions in the RMNP. Remember that both he models showed a negative relationship between increasing summer minimum temperature and elk population densities, which means the elk herds will not likely realize this population expansion. As the world’s environment changes so will the ecology of the worlds regions, this will lead to the expansion of coniferous forests, and the reduction of tundra (Wang, Thompson Hobbs, Singer, Ojima, & Lubow, 2002). This alteration in environmental conditions will undoubtedly lead to a cascade of changes in American elk species abundance, ecology, and epidemiology.

 Society needs to consider crucial elk habitats prior to development so we do not lose the extant species of North American Elk, scientist need to continue research in Chronic Wasting Disease, and be aware of the impact of the changing environment.

References

Britanica, E. (n.d.). A male American elk (Cervus elaphus canadensis) in Yellowstone National Park, Wyoming, U.S. Retrieved from https://www.britannica.com/animal/elk-mammal#/media/1/184943/119637

Cosgrove, M. (2018, 12). Map of CWD in N. America. Retrieved from CWD-info.org: http://cwd-info.org/map-chronic-wasting-disease-in-north-america/

Hermans, A. P., Lee, A., Dixon, L., & Hale, B. (2014). Wolf Reintroduction: Ecological Management and the Substitution Problem. Ecological Resoration, 32(3), 221-228. Retrieved from https://muse-jhu-edu.ezaccess.libraries.psu.edu/article/552436/pdf

Inden/Miles, M. (n.d.). A resident herd of elk in Rocky Mountain National Park in Estes Park.

Moore, J. S., West Greenlee, H. M., Kondru, N., Manne, S., Smith, J. D., Kunkle, R. A., . . . Greenlee, J. J. (2017). https://bioone-org.ezaccess.libraries.psu.edu/journals/Journal-of-Wildlife-Diseases/volume-53/issue-3/2016-07-167/A-Mortality-Event-in-Elk-Cervus-elaphus-nelsoni-Calves-Associated/10.7589/2016-07-167.full. Journal of Virology, 91(19). Retrieved from https://jvi.asm.org/content/jvi/91/19/e00926-17.full.pdf

NPS. (n.d.). A sickly female. National Park Service.

NRCS;. (1999). American Elk (Cervus elaphus). Fort Collins: USDA Natural Resources Conservation Service. Retrieved from https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_010000.pdf

Pulford, B., Spraker, T. R., Wyckoff, A., Meyerett, C., Bender, H., Ferguson, A., . . . Zabel, M. D. (2012). DETECTION OF PrPCWD IN FECES FROM NATURALLY EXPOSED ROCKY MOUNTAIN ELK (CERVUS ELAPHUS NELSONI) USING PROTEIN MISFOLDING CYCLIC AMPLIFICATION. Journal of Wildlife Diseases, 48(2), 425-434. Retrieved from https://bioone-org.ezaccess.libraries.psu.edu/journals/journal-of-wildlife-diseases/volume-48/issue-2/0090-3558-48.2.425/DETECTION-OF-PrPCWD-IN-FECES-FROM-NATURALLY-EXPOSED-ROCKY-MOUNTAIN/10.7589/0090-3558-48.2.425.full

Stahler, D. (n.d.). Strength in Numbers? National Park Service.

USGS. (n.d.). Climate Change and Elk Herds. United States Geological Survey.

Wang, G., Thompson Hobbs, N., Singer, F. J., Ojima, D. S., & Lubow, B. C. (2002). Impacts of climate changes on elk population dynamics in Rocky Mountain National Park, Colorado, U.S.A. Climatic Change, 54(2), 205-223. Retrieved from https://search-proquest-com.ezaccess.libraries.psu.edu/docview/198504042?pq-origsite=summon&accountid=13158

Balvin G. (Director). (2012). Elk Buguling in Rocky Mountain National Park HD [Motion Picture]. Retrieved from https://www.youtube.com/watch?v=TSpGd9p17n0&feature=youtu.be

Map Data:

Elk Habitat 2018 by Rocky Mountain Elk Foundation (RMEF):  https://pennstate.maps.arcgis.com/home/webmap/viewer.html?layers=55a472fa9b084fac9080cf10122645d0 

Historic Elk Range 11 by RMEF:  https://pennstate.maps.arcgis.com/home/item.html?id=15f62c963c0347fcb35da3d503e2ea2d 

Change in Snowmelt Timing by tboucher:  https://pennstate.maps.arcgis.com/home/item.html?id=9c1fd9d8ab9d4f6fbe0be9e2d184c8c1 

Precipitation Change by 2050 by tboucher:  https://pennstate.maps.arcgis.com/home/item.html?id=755c4a1587b1498ba31cadf9de51d339