As I mentioned in previous posts, I have been interning at Black Rock Forest for several years. For the past year, I have worked with the forest manager, John Brady, in assessing the deer population at the forest. Using a variety of techniques annually allows us to determine several aspects of the deer population in order to try and generate a complete understanding of the deer at the forest. Some of these techniques are the deer tracking census, spotlight census, and information from the hunting take.

A method started at Black Rock in 1988, the deer tracking census (DTC), is a way to create an index of over-wintering deer.  The DTC is performed at 12 and 24 hour intervals after each snowfall.  

John and some others ride along roadways in the forest to observe any deer trails in the snow. The roadways are a great place to observe the number of deer in a group because although deer travel single-file, when they reach roadways they tend to disperse and cross at different places on the road. Any tracks seen are scrutinized to determine the number of deer in the group and the direction they were heading. The important data collected from the DTC is snowfall in inches, distance in miles, number of deer, deer per mile, number of groups, and deer per group.

The spotlight census was a method used at Black Rock first in 1986. It involves a truck, a driver, and two spotters who ride along pre-determined routes of about 8 to 10 miles on the forest dirt roads for 10 consecutive nights. The two spotters are next to the two 200,000 candle power spotlights that allow for 500 feet of vision. The spotlight census is performed in mid to late August when buck antlers are well developed and white-spotted fawns travel with the does. Some important information collected from this method is total deer sighted, number of nights, average number of deer per night, total miles, and number of deer per mile. Also, the number of antlerless deer, fawns and bucks are taken which allows us to determine the doe to fawn ratio and the sex ratio, or ratio of males to females, in the population. The error in this method is the lack of visibility due to the leaves being on the trees.

Hunting take is also referred to as hunting harvest, which means the deer killed by hunting. It provides very valuable information about the health and composition of the herd. Average weight (internal organs removed), live weight, heart girth, number of antler points, and antler beam diameter are all obtained by collecting data at the deer hunting station. These all provide information about the health of the herd. It is important to look at the data for the health of yearlings because their health will reflect the amount of resources in the forest for the past year. Other important information collected from hunting is the total of each age class harvested for males and females and fawns as a percentage of antlerless take.

These are general descriptions of the annual methods used to assess the relatively small deer population at Black Rock Forest. As one can tell, each of these methods can have a degree of error. However, each technique allows for different information about the herd health, composition, and reproductive rates. An assessment of the deer population is necessary in order to estimate the current population size, predict the population size in the following year, and create an effective management plan.