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Old 01-10-2018, 10:52 PM   #203
Blackmouth
Six Point
 
Join Date: Feb 2009
Location: Waxahachie, TX
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As far as demographics of the herd, every working day in August, every deer that can be positively identified is counted as buck, doe, or fawn. This was typically done at daybreak and evening before the spotlight counts. During the spotlight surveys which at a minimum included a driver and 2 observers in the back of a truck, deer were counted and identified. If 1 deer in the group wasn't identified, no deer were counted toward the demographics.

For the density, lines were created in coordination with TPWD and researchers from SWT back in the late 90's. These lines have been used ever since. There are 4 lines, each line is conducted a minimum of 3 times and usually 4 times during the month of August. Each night, the lines are driven and the observers in the back scan on each side of the truck and count every deer seen.

Traditional methods would take visibility with a laser range finder every 0.1 mile of each route and calculate acres of visibility from those measurements. In 2016, the visibilities were increased to every 100 meters to attempt to get even better representation of the visibility. This also was done since visibilities likely increased with all the brush management. Then based on that visibility, a buffer was created based on the average distance from the road that the visibilities were measured. When the surveys were conducted, a GPS point, distance and direction were taken of each group of deer. The points are then imported into GIS to show exactly where those groups of deer were observed on the landscape. If the deer were within that buffer, they are counted toward the density, if not, they weren't. By counting only the groups in the buffer, you are only counting the deer within the visibility parameters that have been measured with the range finder.

This is more intense than what TPWD does for the county lines and is the same method used year after year. Although it isn't perfect, it does provide trend data to see what the population is doing. No one knows the best method to estimate deer populations although they are probably the most studied animal in the world. The population on Bullis is strange as the numbers up north of Cowgill are much lower than the numbers down south hence the quota and changes to the hunting program this year. This peculiarity with the deer numbers is a big reason for the collared deer research on Bullis.

I can provide more information if you would like but hopefully this will provide some insight to how the surveys are done.
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