Deer Surveys – Counting and Estimating Deer
Deer surveys are often one of the most lacking components of an effective deer management program. Deer surveys in themselves are not that important, but it’s the estimates of the local deer population that are the most important. Without an estimate of the number of deer living on your property, then it is impossible to administer long term management of the population. Why are population estimates so important? Well, the numbers are needed to track increases and decreases in the deer herd. If a manager is unable to quantify the deer population, then it is unknown whether harvest is warranted. Although deer surveys sound impossible, they are needed. And although surveys are not 100% accurate, most survey techniques tend to under-estimate local deer populations. As such, they are good for estimating a minimum population size.
Deer Survey Overview
So how does one survey deer? In most areas the predominant technique for obtaining white-tailed deer density is mobile spotlight surveys. This deer survey method involves one driver and spotlighters/observers in the back of a pickup or on multi-passenger ATV. Spotlight routes must be set up prior to the actual survey taking place, and the length of the route and the amount of visible area must be calculated. The spotlight route should be representative of the property and cover all available habitat types. In addition, the deer survey should not show bias towards areas where observers believe deer will be, but rather a comprehensive survey of all types of habitat on any one property.
Spotlight surveys are conducted at night and should start one hour after official sunset. It is assumed that deer are scattered randomly across the landscape. With this assumption, it is assumed that the density of deer in the area you count is equal to the density of deer in areas that you do not count (or can not see). To calculate area surveyed, every one-tenth of a mile (along the survey route) visibility data should be collected. To do this, an observer should estimate or use a range finder to estimate how far to both the left and the right an observer could see a deer. In short, use the average distance to the left and right that an observer could see a deer. If at 0.1 miles down the route you can see 50 yards to the left and 60 yards to the right, then those are the visibilities for that point. The total width of the survey route at that point would be 110 yards. Continue collecting these numbers to the end of the route and then calculate the area that will be surveyed by taking the average width of the route by the length. Calculate this area in acres.
Before the survey is conducted, the total area that will be surveyed should be known. Then, it’s just a matter of starting one hour after sunset and counting deer. Make sure to record the number of bucks, does, fawns, and unidentified deer. In addition, do not guess the sex or ages of deer. If you are unsure, enter the deer as unknown. Repeated guessing will skew the data. It is not as important to accurately age and sex deer on a spotlight route because the survey technique is best designed for estimating deer density. Other survey techniques are better for collecting herd composition.
Herd composition is very important for proper deer management. Buck to doe ratio, fawn production, and even deer condition can be determine using incidental observations. This survey technique is unstructured, but relies on observers recording random deer encounters while on the property. All white-tailed deer survey methods should be conducted prior to the fall hunting season, and usually from mid-August to mid-September. To collect incidental observations, any time someone is on the property during the period specified above, they should have a data sheet to record observations incidental to their other activities. Observers can also driver the property during peak deer moving times (early morning and late evening) to collect additional data. At least 100 incidental deer observations are needed for a realiable survey.
Once deer density is estimated using the spotlight survey technique, then the herd composition data can be applied to the population estimate. For example, if a property was 500 acres in size and 10 deer were observed on a spotlight route that covered 100 acres, then the total estimated population would be 50 deer because the spotlight survey estimated 1 deer per 10 acres. Then, if you had collected 100 incidental observations and 20 were bucks, 40 were does, and 40 were fawns, then the population is 20% bucks, 40% does, and 40% does. Apply these percentages to the estimated population and the herd estimates would be 10 bucks, 20 does, and 20 fawns for a total of 50 deer. This data can then be used in your deer management program to keep your herd at carrying capacity.