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Analytical Bighorn Sheep Terrain Selection Report

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Updated: Jun 8th, 2019


People often take nature and its elements for granted. As a result of negligence and the inconsistent analysis of wildlife, a number of species disappear every year. Although bighorn sheep are not yet on the verge of disappearing, the number of their species is declining rapidly due to the changes in the habitat.

With the help of a careful evaluation of the data represented in the histograms concerning the change in the habitat and the effect that this change has had on the bighorn sheep, one can come up with the solution for the threats that the bighorn sheep face and, therefore, protect these species.

Learning what causes the number of species to shrink by analyzing the current statistics will lead to developing a strategy for making bighorn sheep more numerous. An analysis of the change in habitat and the way in which bighorn sheep adapt to this change will lead to solving the existing problems.

Introduction: Bighorn Sheep Need Help

One of the animals that can be found only on the North American continent, the bighorn sheep play a major role in the formation of the U.S. landscape and ecology. According to the existing evidence, the genesis of the bighorn sheep dates back to the 500.000 B.C. (Ulrich, 1986, 22). Since then, they have been an integral part of the American landscape and, therefore, have had a huge impact on it.

However, over the past few decades, a decrease of the bighorn sheep number has been noticed. Despite the undertaken measures, the number of bighorn sheep continues to reduce (Ross & Pearthree, 2009, 49).

With the help of habitat modeling, one can distill the factors that are most likely to induce the decline and, therefore, save the bighorn sheep population. It is crucial to use the method of terrain selection, since topography is an important variable in the analysis of wildlife ecology that shows the species dispersion and allows for a more or less accurate prognosis.

Methods: Nature through the 3-D Glasses

Results: Bighorn Sheep and the Probable Changes

According to the random_elev model, in which null distribute was applied on elevation, (349.2 – 1423.8 m); as the results of the research say, a great amount of sheep was counted at the elevation of 700–1300 m. Therefore, it can be concluded that the bighorn sheep prefer higher elevations, starting from 700 m.

As for the sheep_elev slope, in which the actual pints have been covered, bighorn sheep were mostly found at the elevation of 368.3 to 840.2 m, while the overall elevation range at which bighorn sheep usually dwell was 368.3 to 1100 m.

Considering the graph of random slope, one can come to the conclusion that it is predicted that the greatest number of bighorn sheep can be spotted at the elevation of 2435 m (58 and more). In addition, a great number of sheep (30–54) was spotted at the location of 7,305–31656 m, though with the increase of the elevation, the number of sheep declines considerably, starting from the point of 17,046 m.

Weirdly enough, the actual results appeared quite different from the anticipated ones. According to the graph of sheep_slope, the greatest amount of sheep was observed at the point of 34.778 to 52.167 m, peaking from 54 to 78 sheep. The difference in the anticipated data and the obtained one can be explained by the fact that the initial graph did not take into account the recent changes in environment.

Thereafter, to analyze the relevance of elevation to the wildlife and the effect on the changes in elevation on the local inhabitants, bighorn sheep in particular, the following procedure was carried out:

  • Opening a new ArcMap;
  • Add the following data from the „LAB11/Bighorns‟ directory:
  • „loom5‟- a digital terrain model layer of the study area
  • „randompts.shp‟- a layer of random points generated in a statistical programming environment and imported as a shapefile.
  • „Mar2010all.shp‟- a layer of locations of 10 individual sheep from March 2010.
  • Performing a stretch on the „loom5‟ data if necessary to make it more interpretable by eye.
  • Displaying the point data by „SheepID‟, which is the GPS collar code for each sheep

After the following procedure, an image, which showed the distribution of the actual bighorn sheep locations, was produced. The actual location was defined by putting GPS collars on some of the bighorn sheep and, thus, tracking the pattern of their migration.

The elevation function obtained from the analysis of the given information can be considered another crucial variable together with the background distribution; comparing the two will lead to acquiring essential data concerning the change in the bighorn sheep habitat.

Analyzing the information offered in the graph, one must mention that the actual location of the bighorn sheep is quite close to the predicted one; however, it is still worth noting that the spectrum of the predicted locations was much broader than the actual one.

In addition, the red dots showing the supposed location of bighorn sheep are scattered all over the map, while the purple ones that show the actual location of the bighorn sheep clearly follow a specific pattern. However, the elevation of the given spots still remains to be analyzed; that is, the spatial data must be obtained. For the analysis of the actual spatial data analysis to be completed, the following procedure must be carried out:

  • Making the following steps in ArcToolbox: Spatial Analyst>Extraction>Extract Values to Points‟.
  • Extracting the elevation values from the „loom5‟ grid layer to both the „Mar2010all.shp‟ and the „randompts.shp‟ shapefiles. (Note: this is done in two steps).
  • Giving the new random point shapefile (now with elevations) a file name like „random_elev.shp‟.
  • Giving the new sheep location point shapefile (now with elevations) a file name like „sheep_elev.shp‟.
  • Opening the attribute tables for both point layers to answer the following question: “Where do the elevation values go?”
  • – Considering the histogram for the random elevation values in ArcMap.
  • In the attribute table, going to „Options‟ and select „Create graph‟.
  • In the wizard:
  • Setting „Graph type‟ to „Histogram‟.
  • Making sure „Layer/Table‟ corresponds to „random_elev‟ or whatever you called it.
  • Setting „Value Field‟ to „RASTERVALU‟, since it contains the appended elevation values.
  • Working all the way through the wizard, and click „Finish‟.
  • Doing the same for the sheep location elevation values.

In the process, two graphs were produced. In the graph of random_elve, i.e., he chart in which the supposed results concerning the bighorn sheep location are placed, the estimated location with the greatest amount of sheep is the one at the elevation of 349.2, 492.483, 564.125, 922.333, 1,065.617 and 1,208.9 m.

It is important to add that at the elevation of 1.637.75, 1,853.675 and 1,996.958 m, the smallest amount of bighorn sheep is predicted to be found. Therefore, though one might have thought that, with the raise in elevation, the number of bighorn sheep declines, the problem is actually a bit more complicated than that.

As the research shows, at the specified elevation, certain factors prevent bighorn sheep from populating the given places. It could be assumed that at the given elevation, the specifics of the landscape do not allow for the opportunities of finding shelter and hiding from predators. However, the actual location of the bighorn sheep turned out a bit different from the predicted one once again.

In contrast to the previous table, the one displaying the actual location of bighorn sheep has shown that the greatest amount of sheep is located at the elevation of 637.983 m and 536.852 m. At the elevation of 1.312,19 m, however, the smallest number of bighorn sheep was registered.

The given discrepancies in the data from the two tables show that at the specified ranges, the weather conditions, the landscape specifics or any other factors inducing the migration of sheep to further locations exists.

Finally, analyzing the slope angles, one must mention that, according to the research results, sheep use slope angles in proportion to availability, which can be explained by the unevenness in the location of food consumed by the bighorn sheep.

It is important to keep in mind, however, that the given information dates back to March, 2010. Over the past three years, a number of changes must have occurred, triggering the change in the bighorn sheep location.

It could be assumed that, due to the climate change and the temperature increase, the plants consumed by the bighorn sheep grow on much higher elevations, which could have triggered the elevation of the sheep location as well (Feldhamer, Thompson & Chapman, 2003, 1105).

Literature Cited

Feldhamer, G. A., B. C. Thompson & J. A. Chapman. 2003. Wild mammals of North America: biology, management, and conservation. John Hopkins University Press, Baltimore, MD. 1216 p.

Ross, C. & P. Pearthree. 2009. A geologic and natural history tour through Nevada and Arizona along U.S. Highway 93 with GPS coordinates. University of Nevada, Reno, Reno, NV. 175 p.

Ulrich, T. J. 1986. Mammals of the Northern Rockies. Mountain Press Publishing, Missoula, MT. 157 p.

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