Springtime usually brings some much welcomed warmer weather to Frost Valley. Emerging from the soil along with this warmer weather are the beautiful spring ephemeral plants. The presence of these plants represents a short window of time before the forest canopy fills in and summer foliage takes over. This is deer density survey time, and it is a literal race against time for the Natural Resources and Environmental Science Department. The race begins as soon as maple sugaring season is over (April 5th this year) and must be finished before the ferns fill in and block our view of the forest floor. An adequate area of the forest floor must be surveyed during this relatively short time. The results of these surveys are an important tool for making wildlife and forest management decisions.
- Conducting a deer density survey is actually quite fun. The method we use at Frost Valley is a pellet count survey. Also known as… counting poop piles! Data collection consists of walking in straight lines across various sections of the property and stopping every 100 feet to survey an area within a 4 foot radius. We refer to these straight lines as transects or transect lines. To survey a transect, we simply set a compass bearing to the desired line and follow it. We then pace out 100 feet, stop to check a plot of 4 foot radius, then pace out the next 100 feet before stopping again to survey another plot. The whole time recording every plot surveyed and every pellet group counted. Pellet groups counted must contain more than 10 pellets, at least half of the pellet group must be inside the 4 foot radius survey area and the pile must be on top of the leaves. No digging through the leaves or taking extra steps to count more poop!
- After all the transect lines have been walked, the results can be calculated. In order to do this, we need 4 pieces of data. We need to know the average number of pellet groups deposited per day by a single deer. Penn State University has determined this number to be 25, so that is the figure we use. Next is the number of days since leaf off. We keep records of this in the fall. The next figure needed is the number of pellet groups counted within the plots sampled. Lastly, we need the total area of sampled plots. Now we can calculate the deer density of the property!
Deer Density (per square mile) =
# Pellet Groups Counted
Pellet Groups Per Day x Days Since Leaf Off x Square Miles of Plot Area
This year it worked out to 11.1 deer per square mile, a bit higher than last year’s estimate of 8.3. It is important to note that when looking at this information, one should not place too much certainty in the results of one year alone. The purpose of conducting these surveys is to achieve better insight into the trends of our deer population over time rather than provide a snapshot of the current population. From year to year these numbers could jump around quite a bit. We could have a complete anomaly and get incredibly low or high density numbers in a particular year. However, over the course of many years or decades, having this large scale perspective is extremely valuable and helps us to achieve an accurate assessment of the trends in our deer population.