Could you explain a properly run long-term camera census? From stuff I've read with QDMA, it has pouring corn out over a 2 week period in front of cams to calculator the heard.
That was the original baited census technique, developed by Dr. Jacobson and first published at the 1999 Southeast Deer Study Group. For a while, that was
the technique for camera censusing deer populations. However, three problems were found with this technique. First, some deer won't come to corn piles. I first started noticing this while censusing individual properties. I was getting a few older bucks only in the background and never at the corn. Eventually I sent up a test where I ran two censuses concurrently on the same property, one with corn piles and the other salt licks. I found that the corn piles never got a buck older than 2 1/2, while the salt licks were getting mature bucks. In areas where deer are being baited during hunting season, older bucks learn to avoid them like the plague.
A second problem was the calculations. Because unique does cannot be identified on camera, but bucks can (by their antler characteristics), a repeat photograph calculation is used to estimate the number of unique does. The assumption is that bucks and does will be repeat photographed at about the same rate. With this being the case, the number of unique does can be calculated using the repeat photograph rate of bucks. For example, if you have 80 buck photographs, but you have only identified 10 unique bucks in those 80 photographs, the repeat photograph rate is 8 [total buck photographs / unique bucks = repeat photograph rate]. The total number of doe photographs can then be divided by 8 to get an estimated number of unique does in the population. The same is done for fawns. However, tests with marked does found that does stay at the bait sites much longer than bucks, producing far more repeat photographs per unique doe. This throws the calculations way off, suggesting you have far more does than you really have.
The third problem - and a
MAJOR problem - is seasonal range-shifting. Baited censuses are run in August, when bucks' antlers are nearly finished growing (making them more identifiable), but before the first acorns begin to fall (which draws deer away from the bait piles). But what if the local deer shift ranges dramatically from summer to fall? This is especially a problem when censusing smaller properties. The baited census gets an accurate census of the bucks using the property in August, but the hunting season buck population may be very, very different as bucks shift ranges summer to fall, as well as during the rut. In some situations, MANY more bucks may use a property during hunting season than were using it during an August baited census. In addition, some of those bucks using the property during the summer baited census may have shifted miles away by hunting season, hence are not huntable, manageable bucks.
To try and solve these problems,
especially the last one, I started working on a new census technique many years ago (the Fall of '99 to be exact). For lack of a better term, I just called it the "season-long unbaited census." Although I've never published my data, talking about it here on TNdeer and the QDMA's talk forum sort of "spread the idea around." The season-long unbaited census still works like the 2-week baited census except that no bait is used to draw deer in front of the camera, and the census is run all hunting season. And running the census all hunting season is critically important. The point of the census is to inventory the bucks that are huntable and manageable, which means ALL the bucks using the property during the entire hunting season. Now, without question, there are some real difficulties associated with a season-long unbaited census. First, it requires running cameras over a long period of time (labor, batteries, etc.). Second, it requires more cameras because you are not using bait to draw deer in front of the camera. I found that with a baited census using salt licks, I could get a good late summer census with just one camera per 160 acres (four per square mile). However, I needed to double the camera density to get a good unbaited census (1 per 80 acres). And even more than that is better. In addition, a strong understanding of what habitat and terrain features concentrate deer movement in the area is needed. Because bait is not used to draw deer in front of the camera, any other natural feature that concentrates deer movement (food, habitat, terrain, scrapes, trails, etc.) must be used to maximize pictures. In his post, Ski gave some great examples of where to place cameras. Lastly, some of the same problems with the baited census calculations still exist with the season-long unbaited census. For example, in some areas does will frequent food plots more frequently and for longer periods of time than bucks will. This produces skewed sex ratio numbers in favor of females. On the flip side, bucks usually frequent scrapes more often than does, producing skewed sex ratio numbers in favor of bucks. When collecting and analyzing the data, I calculate each herd parameter (sex ratio and fawn recruitment rate)
by camera set-up type. This allows me to see any "weird" numbers that aren't lining up. For example, over the years, as my food plot work has become more efficient, producing better fall food plots, the sex ratio calculations from cameras pointed into food plots has become more and more skewed towards females. However, sex ratio calculations for other camera set-ups have not. This lets me know to take the sex ratio data from food plots with a huge grain of salt. In fact, I graph "total sex ratio" data from all locations AND sex ratio calculations from all non-food plot cameras separately, so I can see the difference. The below graph is a prime example. It is a graph of the adult sex ratio (Does/Buck) comparing the 4 most common camera locations I use. Notice how the "Food Plot" and "Scrape/Food Plot" show climbing numbers of does, but the other two camera set-ups do not. That is an indication the food plots are drawing more does for longer periods of time, not that the sex ratio is actually changing.
