Two Survey Methods In Great Detail
If you are a practitioner of deer management and have been reading this publication very long, then you are well aware of the importance of deer surveys. Deer surveys are surveys, not inventories, meaning we likely will never know exactly how many deer are on your property nor do we need to know that exact number. Deer typically don’t want to be counted and game fences do NOT contain all of them, despite common perceptions. So a survey is done each year at approximately the same time and by the same method so that any changes in the data must be from the deer themselves. A survey is meant to provide estimates, ratios, and percentages and then used to apply harvest pressure to alter those numbers into the desired direction and levels. Texas Parks and Wildlife Department offers specialized permits to assist qualifying landowners and those permits are based on survey data. So know that survey data is mission critical for results-oriented management as well as specialized state issued management permits. TPWD has a list of approved survey methods and the three most used methods for whitetail deer include spotlight, trail camera, and helicopter. Each method has specific guidelines to be used in order for the data to be of value, but each technique also has advantages and disadvantages. For this article’s purposes, let’s look only at the spotlight and the helicopter survey method.
Spotlight surveying is popular because it was one of the original techniques developed back before the time most people reading this were even born. It involves driving a preselected route on your property while shining two spotlights into the brush and identifying and counting observed deer. It involves three people--one to drive and record the data and two to shine the lights and count. The predetermined routes are oftentimes the primary ranch roads and the distance observable under each spotlight is measured and calculated to determine the exact number of acres actually observed under the spotlights’ beam. The number of deer observed within this “acres of visibility” is then extrapolated to the total number of acres of the whole property. And herein lies the “cons” of spotlight survey method—TPWD requires the survey route to be performed no less than three separate occasions, so that means nine “man days” (females are obviously welcome and the work is late into the night but that is what they call it!) so the labor portion is indeed expensive. Next, the majority of ranch roads, especially in the hill country, are located in the bottomlands--the better soil areas that do not typically include the roughest of slopes and cedar-choked canyons. The deer themselves live on the slopes and in the canyons but oftentimes travel down into the better soil areas at night to forage on forbs, feeders, and food plots that are also located near the primary ranch roads. A typical spotlight route will cover 10-12% of the total acreage of a property. So you and your buddies start the spotlight survey route just at dark (remember, deer are crepuscular, meaning they prefer to travel at daylight and again at the onset of darkness, thus why we typically hunt them twice per day) so as the spotlight effort begins, the deer also begin to travel down from the rough country and into the more open areas with prime soils. As you drive the survey route you begin to collect deer sightings and record them. Under a spotlight, deer are not easily identified unless they are close or in the clear.
“ Is that a middle-aged doe or a spike buck? Is that really a big fawn or a small yearling? When that group of bucks ran away from the spotlight, were there two does in with them or two different spike bucks? What approximate ages were all of the bucks? How many points did those two big ones have? Is the fawn traveling with the doe or was it lagging behind her twenty yards and still in the cedar thicket, or did she not produce one this year? In that tall bluestem grass, is that one or two sets of deer eyes or is one a rabbit? Since we didn’t see any coyotes, does that mean we don’t have any because I hear them every night just west of camp. I see feral hog sign at all my ponds but we haven’t seen a pig during the spotlight survey yet, I wonder if I really have a pig problem or not?”
After three separate nights of getting to bed at 1:00 am, you finally finish the survey project and compile the data to learn that the actual acreage observed was 120 acres and the ranch is 1,000 total acres, so you did survey 12% of the property as designed and with only three flat tires and one burned out spotlight as collateral damage. On each spotlight night, you averaged seeing eight bucks, fifteen does, ten fawns, and at least six unidentified deer (they ran off, you couldn’t identify them, just saw eyes, etc.) and now the math extrapolations begin. According to the 12% survey effort over three different nights, the computer estimates you have 79 bucks, 148 does, and 98 fawns, or a herd of 325 animals on your property. That comes out to 3.08 acres per deer, 1.88 does per buck, and a 67% fawn survival rate. Now you KNOW this is not correct because you know this ranch and hunt it five months out of the year and work on it twelve months out of the year. If you indeed had over three hundred deer you would know it. Last year the deer you harvested were fat and healthy and the bucks were above average and each time you sat in the blind you averaged seeing only eight to ten deer per sitting so how can there be over three hundred deer???? If I have that many bucks, why can’t I find more shed antlers? And here is the largest con of the spotlight method: remember when you surveyed only 12% of the property that contained the deeper soils, the best habitat and did not include the steep rocky slopes or the cedar thickets where you couldn’t see anything? The computer didn’t care about that or even consider it, it thinks your ranch road bottomlands are the same as your rocky steep sided slopes and we both know they are not the same. So now the harvest recommendations for this fall will be based on the extrapolated spotlight survey data that you know in your heart is not correct, much less accurate, but in order to secure the permits you want, this survey data has to be used. And the projected harvest recommendations for this dataset in order to lower the density to only 6.0 acres per deer will be to harvest a whopping 158 total deer! Your recreational hunting property just turned into a killing field and not many folks, much less deer herds, are able to take on that type of harvest pressure. Using misleading data based on extrapolation is very risky and potentially dangerous from a management perspective.
The helicopter survey is performed only one time during daylight hours and involves flying just over the tallest structures on your property (power lines, windmills, pecan trees) using GPS guidance in a tight grid pattern. Every acre of your property is seen from the bottomlands to the tallest hill and into the thickest of brush but not every deer is observed. Some deer refuse to flush and remain hidden, some deer run far in front of the helicopter and some deer may run back and forth in areas you have or have not yet counted so we do not see every single deer on the property even though we do see every acre of the property. The low flying helicopter flushes most animals and the four observers (three observers plus one pilot) easily see any movement below. Deer are positively identified from above and in the daylight so guessing is avoided. The helicopter can stop, hover, back up, turn around as needed to ensure accurate identification and video or still cameras can be used to record the effort or to photograph specific animals (see photos found in this Guide). Because we can observe every acre on the property, we can check all fences, water sources and livestock as well as ensure nothing is stuck in the mud, check deer blind doors and windows, check feeder lids, and count coyotes and feral hogs to determine not only how many but also where on the ranch they live. After the count, we can return with firearms to dispatch predators (this requires a permit ahead of time) and can lift up and take aerial photos of the headquarters, terrain, proposed habitat projects, and see the “lay of the land” to really understand how and why deer live where they do. It is great for placing new blinds, feeders and food plot locations because you can see the soil changes, the habitat flow, observe travel corridors, and generally improve your understanding of the entire property. And on the same 1,000 acres that took you three late nights and three flat tires to see only 12% of the acreage with the spotlight survey method, we can do IN ONE HOUR with a helicopter! From a biologist’s perspective, observers can easily identify the fawns from the yearlings, can separate the yearling bucks into spikes versus not spikes to see the percentage of spikes in the yearling cohort, can identify the middle aged bucks from the mature bucks, and can even count the mainframe points of each mature buck! I can quantify the age structure of the buck herd, the mature buck quality and most importantly, I can see the body condition of every buck observed among the age classes. I can photograph bucks to target for harvest and photograph the trophy bucks. The GPS map (see photo) also shows you WHERE on the property the photographed bucks are located so you can better understand deer distribution and learn why they prefer that part of the ranch over others. We can easily count the does and fawns to accurately assess the fawn production rate and age distribution of the female cohort. If you have ear-tagged deer or exotics, we can count them separately, as well. So the helicopter survey method is much more than just a deer survey, it is a complete and total ranch survey that sees every acre you own and so much more. If you do have a predator problem we can fix it within minutes of knowing about it or can plan to return at a later date for that specific purpose. We can count quail and turkey and notice where water prefers to flow so a future pond can be built. We can see whitebrush thickets that can be cleared or how the deeper soils that run in bands at the bottom of the rocky hills can be used for improved grasses or even new food plots.
Oh, and that same 1,000 acre ranch that the spotlight survey said you had over 300 deer on it? The helicopter survey counted 77 total deer for a density estimate of 12.9 acres per deer with an adult sex ratio of 1.1 does per buck and a 53% fawn survival rate. Since you know the ranch so well and have been monitoring the deer herd for years, you know that the helicopter method reflects much more accurately what you observe than the extrapolated method using only 12% of the whole ranch.
Conclusion: The spotlight method does have value on small and mid-sized properties where the habitat is consistent throughout. If the line is set up well and passes through the majority of any changing landscape, it can be used with success. However, if the ranch is large and habitat diverse, the spotlight method is not recommended and even can be dangerous if taken out of context.
The spotlight survey tends to over-estimate the deer herd and does not use precise known data (misidentified deer, unknown deer, etc) while the helicopter survey tends to under-estimate the deer herd but uses positively identified deer. The spotlight survey is expensive in terms of labor and time while the helicopter method is cheap in terms of time and labor but financially more expensive. The spotlight survey “sees” only a small percentage of the property while the helicopter covers every single acre of the ranch.
When considering a survey method, heavy consideration should be given to the desired outcome. Do you simply need generalized data only for permit issuance sake or do you desire more specific data and want to see your entire ranch investment in just an hour or two in order to gain more detailed knowledge about your deer herd, habitat, and total ranch overview? Each survey method has pros and cons that deserve serious consideration because not every ranch, or ranch goal, is the same.
Posted in: Land Management