Conduct a Deer Census with a Trail Camera

How quickly things can change. A decade ago deer hunting in Iowa was at its peak, times were good, deer were plentiful and stories abound every year about giant bucks being killed. Lately hunters have been telling a different kind of story. Not about the abundance of big antlers on their hunting ground, but rather the lack of any kind of deer. How did this happen? Overhunting in previous years? Two consecutive years of drought? Spawning EHD epidemics? Too liberal of quotas on does by the State of Iowa? The HUSH program which made donating deer a popular practice?

You could make a good argument for any or all of these potential causes. As deer hunters, we want to believe that some outside forces are responsible for the downturn in deer numbers. But I’ve been thinking lately about my responsibility in all of this. Where did I go wrong? As I sit and review my trail camera library for the past several years, contemplating the answer to why this has occurred, I realized that I’m missing something in my scouting efforts. My strategy was all about tracking bucks and identifying the “shooters.” I completely ignored the female side of the herd. I would venture a guess that most hunters do the same.

So, what does scouting the whole herd have to do with deer numbers? It is the only way to accurately estimate how many deer should be taken. Without this information, we are operating blind with no real facts to back our decisions to pull the trigger. In essence, my eureka moment was when I realized that I should I stop taking someone else’s opinion of what needs to happen to my local deer herd and instead start doing my own due diligence to make up my own mind of what is best for my farm. After all, a farmer doesn’t just blindly buy the hybrid seed the sales representative is pitching. He looks at many different factors, weighs his options and selects the plan that most benefits his farm. Why am I not doing that same thing with what I am trying manage?

So, how exactly do you go about figuring out how many deer should be taken in a given year? The answer is to conduct a census of your property. A deer census is an information-packed tool for learning the make-up of your property. By using trail cameras, the results will reveal herd health, herd density and buck-to-doe ratios, among other data. In addition, it will help you analyze your past deer harvest decisions and determine your strategy for the coming season. Over time, you can determine trends and pro-actively respond to what you learn. It’s all part of Quality Deer Management (QDM). You are the steward of your land, and it’s up to you to make the right decisions based on quantifiable data.

Drs. Harry Jacobson and James Kroll pioneered research on trail-camera census methods. While visiting with Dr. Kroll, aka Dr. Deer, he explained, “Since we invented trail cameras in the 1970s, we have used these valuable tools for a multitude of purposes, including patterning whitetails, studying deer behavior, evaluating the effectiveness of products, censusing whitetails, and management/ demographic studies. I cannot envision being an effective hunter and manager without them."

The steps to a trail-camera deer census are simple, but the survey is based on science and requires proper planning before you start. The following bullet points are based on Drs. Jacobson and Kroll’s published findings. I’m outlining the basic steps, but I encourage you to read an in-depth explanation in QDMA’s book, “Deer Cameras: The Science of Scouting,” which is available to purchase at www.qdma.com This is where I learned how to conduct a deer census for my property.

Census Preparation

• There are two ideal times to conduct your deer census. Choose one. The pre-season survey (late summer/early fall) will help you determine specific hunting locations and a “shoot/don’t shoot” strategy for the upcoming season. The post-season census (winter) allows you to see which bucks made it through the hunting season.
• Do not conduct your survey when natural vegetation is readily available to the deer herd. You want the bait to lure them to your trail camera locations so you can capture images of as many deer as possible. Most hunters would think that the late summer/early fall would be considered a plentiful time of year, however this is not the case. This is an ideal time to conduct a census, just make sure your census is completed before the acorns start to drop.
• Gather trail cameras. You’ll need one camera per 100 acres of land. If your camera is equipped with “burst mode,” use this setting. This will allow you to capture multiple images of the deer as it feeds or passes by the bait pile. If your camera is not equipped with “burst mode,” make the delay between pictures as small as possible.
• Choose an easy-to-access location where you can still conceal your trail cameras from the deer. We don’t want our deer herd to be alerted by the camera and then avoid that location. Hide it with vegetation, and always face it north so that the sun does not interfere with the sensor.
• Assign each parcel and camera a unique number. Use a site marker that will show up in each snapshot so that you can organize your photos by location, thus reducing headaches later on.

Pre-Bait

• Determine bait, and start baiting 7-10 days prior to the actual census. The most popular bait is corn. Follow all baiting and feeding regulations in your state.
• Your goal is to ensure the bait is attracting the deer to the location and the cameras are producing photos you’ll be able to use.

Survey

• Conduct the actual survey phase for 14 days. According to QDMA, a 14-day survey period will allow you to capture images of 90% of all unique deer. Your goal is to capture images that help you sort the herd by sex, age and antler size.
• Monitor trail camera locations to refill bait, change camera batteries and replace memory cards. Use caution when visiting the sites, just as you would a hunting stand.

Analyze Results

• After the 14-day survey, collect all images. Count the number bucks, does and fawns (the “total” includes repeats of individual deer). If you cannot definitively identify if the deer is a buck, doe or fawn then count it as “unidentifiable.” That’s ok.
• Spend time, and it may take a lot of time, to study the photos and count the number of unique bucks. If you were to count 100 total bucks, but only 10 were unique bucks, then your ratio of unique bucks to total bucks would be 1:10, or 10 percent.
• Use that same ratio to determine the number of unique does and fawns on your property. For example, if you counted 200 does, then using the above 10 percent ratio would produce 20 unique does.
• Adjust those numbers to account for deer your camera missed. If you ran the survey for 14 days, take the unique numbers of bucks, does and fawns and multiply times a factor of 1.11 to determine a more accurate total count of deer in the herd. If you ran the survey for 10 days, use a factor of 1.18. A 7-day survey should use a factor of 1.25.
• In analyzing the sex ratio of your deer herd, your goal should be a balanced one. A 1:1 doe:buck ratio is ideal. Understanding this ratio can tell you if your management efforts are heading in the right direction.
• The fawn:doe ratio is the most critical population number to understand. Knowing your fawn recruitment (the number of fawns that survive for at least six months) dictates the harvest rate you can apply to your herd. The higher your recruitment rate, the more deer you can harvest. The average recruitment is 1:1 fawn:doe ratio. Low fawn-to-doe ratios suggest that something is missing in your management plan. You need to increase fawning habitat, improve available nutrition or reduce predator populations.
• To determine the number of deer per square mile, use this formula: Number of Total Deer multiplied by 640 divided by Number of Acres Surveyed. Your first census will create a baseline. Use subsequent years’ surveys to understand the trend line for your deer herd. If the density is declining and you are trying to increase the number of deer, then reduce your harvest of does.
• Repeat your survey annually, at the same time and same locations, so you can develop trends and find patterns within your deer herd.

A deer census is a valuable management tool. Interpreting the data and tracking it over time is what separates hobbyists from deer managers. I challenge you to become educated and true managers of your herd. Be proactive in your habitat decisions and hunting strategies.