Mini Project- Analysis of the Declining Bat Population in Select Counties of Wisconsin

Introduction:

I chose the declining bat population in Wisconsin as my project.  I wanted to research why this is happening and if there are any factors contributing to this.  I chose to see if this decline was based on certain criteria.  The study question is, is the bat population declining in Wisconsin, and if so where and is there something responsible for it.  My hypothesis is that the decline is due to many factors but the most important one is that the increased amount of pesticides are part of the problem and maybe the biggest part.  In my results section I included maps that show that the more pesticides in an area that is where the decline is the greatest.  Instead of finding the most suitable areas for bats, I chose to research the areas where there was a decline. 

Methods:

I used a series of  analysis done by the  Wisconsin Department of Natural Resources to show the amount of bats in each of the counties that had enough data to go on.  In the information I received from the DNR, there were many counties that did not have enough data to use in my analysis, namely Stonefield, Dodge, and Yellow Lake.  These counties only had data for one year or for only a few detection sites and not significant enough to map or analyze.  The counties chosen to analyze to see if there has been a decline in the population of bats are as follows, Grant, Iowa, Lafayette, Trempealeau and Door Counties.

First I analyzed he data from the DNR, then I decided to see if my hypothesis was right that the bat population in Wisconsin is declining.  I did this by adding all the bat radar analysis.  On the nights the researchers went out, they used the counts of bats to see where the bats were and how many.  The researchers went out at least 10 times per site and some other sites they had more visits.  Because of this I normalized the data.  I chose the most recent data provided and did an analysis of 2014 and 2015 to see if there was a difference.  I also used a buffer of 500 feet away from a major road or interstate to see if the bats are staying closer to roads that have trees or it they are staying near trees in the wooded areas.  I then used the Euclidean distance to see if the distance between two points and counted in metric space, I selected the distance from the center of the cities of Wisconsin.  The next tool I used was intersect, I intersected all the buffer zones. 

First is the map I created in ArcGIS with the above counties and the counts of the bats for 2014 and 2015, it shows that the population did in fact decrease.  The map also shows that there are not many bats near larger cities and where many major interstates are present.  If you notice in maps 1 and 2, of Wisconsin Bat Population of 2014 and 2015, the area on the south eastern part of the state has very large populations and there are not bat hibernation cites in this area.  This is also true for the other counties that bat population has been counted in.  Bats tend to be in areas of less human traffic.  The below map shows that the population of bats decrease in Lafayette and Door Counties, there was a small decrease in Iowa county and Grant increased. This increase in Grant County could be due to the amount of increase traffic in Lafayette county or it could be the pesticide use, or many other factors.  The map clearly shows that there is a decrease of over 1,000 bats in Lafayette County. 

Maps 1 and 2:  Shows increase of bat population.  2015 map includes cities of Wisconsin for emphasis. 

 Next, I created a buffer of 500 feet from roads so we could see the if this played a role in the amount of bats in an area.

Map 3:  Buffer zones of 500 feet from major roads. 






 

This map shows the buffer zones and there are no major roads that go through Door County that would make this an issue for bats, the majority of the county of Lafayette is not in the buffer zone yet man of the bats migrated to Grant where there are more roads which leads me to believe that there is another variable affecting the population.

The next tool used was the Euclidean Distance and I chose to use it from the center of a city in Wisconsin.  Below is a map of the areas and how far from the city most of the bats are, if you notice at the bottom left or southwestern part of the image, it shows the distance from the center on Grant, Iowa and Lafayette Counties are not near the center of bigger cities.  Bats need trees or caved areas to live in which are not usually located near large cities. 

Figure 4: Euclidean Distance from Wisconsin cities. 

 

  



 

 

Map 4:  2005 Cropland layer map from the USGS website and cropscape. 

The above map was taken from the USGS website from the National Agricultural Statistics Service.  It displays in dark red the areas where the most pesticides were used.  If you see that this map is from 2005 and the United States uses far more now that before, the focus area, namely Lafayette County is covered in red and that is an area where the population has declined.  This is just another added part of the puzzle to show that there may be a high correlation between the two. 

 

 

Results:

 

The results were just as I thought with the creating a map in ArcMap with the Excel files I used from the WI DNR.  The bat population is declining in the focus area counties, also bats like to stay away from highways and busy cities.  If there is more development of urban areas near bat hibernation cites, the population can further decline.  The maps I provided did show exactly what I wanted them to.

 

 

Evaluation: 

 

This project was much harder than I thought, I had to wait a very long time to get the data and even longer for it to get analyzed so I could use it and make shapefiles for my maps.  I also had a hard time with all of the tools and had to re-run them a few times.  I put in too many variables to do the project properly.  I should have just stuck to where bats are located and why instead of doing the decline, reasons for it and introducing pesticide use.  I chose too many things to discuss and analyze therefore making my project not as understandable and not as easy to do.  It took me such a long period of time to analyze the data to see what I could and couldn't use.  That was time I could have used doing other parts of this assignment.  I had many challenges while doing this assignment because I had too many ideas and too many things involved in the results.  I  would change the whole entire outlook and I would have analyzed other counties in the U.S. not Wisconsin as the Wisconsin DNR does not have much data on the bats and they do not consider bats to be very important as diseases such as White-Nose Syndrome have not hit Wisconsin very hard, doing research on another county that has more data and more problems, then they would also have more information.  I also went out with Chris Floyd to collect data in Eau Claire but since there was so little data and the DNR said that they would need a few months to get the data we collected back to me from the radar collection. I had no idea that this would take that long.  I just over thought the whole thing and I really am not happy with the overall results except for the fact that the counties that use the most pesticides had the most decline in the bat population.  I just don't think overall I had enough information to do what I wanted with the project. 

 

 

References:

 

USGS Wisconsin Pesticide Maps

 

John. P. White, Wisconsin Department of Natural Resources