Over the last decade, predators, especially coyotes, have greatly altered deer population dynamics in many parts of the country by reducing fawn recruitment (the number of fawns per doe that survive to 6 months of age). Not surprisingly, the level of their impact varies from one state to another, and often even from one property to another.
Results from several Midwestern and Northeastern studies indicate that coyotes are responsible for taking, on average, 10 to 20 percent of fawns. This level of fawn predation likely has minimal impact on the overall recruitment rates, particularly in highly productive herds. However, other studies of coyote predation rates, particularly in the Southeast, suggest that coyotes may take a greater toll. Several studies have reported that fawn recruitment rates have dropped from a historic average of 0.9 to 1.2 fawns recruited per doe to 0.4 to 0.5 or less. This equates to a decrease of more than 50 percent in deer herd productivity and certainly has important implications for harvest management, particularly doe-harvest goals.
The results from our studies at the University of Georgia Deer Lab and those of other researchers across the eastern United States clearly demonstrate the high variability in coyote predation rates and subsequently in fawn recruitment. Thus, it is more critical than ever for deer managers to monitor fawn recruitment rates before setting harvest goals. Herd monitoring will allow aproactive, rather than a reactive, approach to accounting for the coyote’s potential impact on your deer herd.
Several simple techniques for estimating fawn recruitment are available to aid in monitoring of recruitment rates. However, none of these are perfect, and each requires an understanding of exactly what information they can provide and how to properly interpret the results.
Many deer hunters know that systematic trail-camera surveys can be used to determine and track deer density and buck:doe ratios. NDA’s book Deer Cameras: The Science of Scouting covers trail-camera surveys in detail. However, using trail-camera surveys to monitor fawn recruitment requires some special considerations.
First, timing is everything. Typical pre-season surveys conducted during late August or early September may underestimate fawns-per-doe because many fawns are still too young to consistently accompany their mothers. Unfortunately, waiting until later in fall to run surveys is usually not an option due to their interference with hunting season. Furthermore, a fall survey coincides with peak acorn drop in most areas, making baited camera sites less attractive. Although the estimate of actual fawn recruitment may be low, pre-season surveys still provide important trend data that – when compared from year to year – can tell you if your fawn recruitment is trending down or remaining stable, as long as you conduct your surveys the same way and at the same time every year.
Post-season (winter) trail-camera surveys conducted after the hunting season may provide a better estimate of actual recruitment. Fawns are much older and more mobile during January and February, and the increased attractiveness of bait increases the probability of photographing the majority of the local deer herd. However, winter surveys also have problems that must be considered. During January and February fawns become much more difficult to distinguish from does, especially yearling does. Thus, care should be taken to study and learn the distinguishing characteristics of does vs. fawns. To safeguard against incorrect classification, we typically go through a familiarization exercise where we spend at least 20 to 30 minutes viewing pictures of antlerless deer on a new property before we begin actual quantification of animals.
It is also important to consider doe harvest when estimating recruitment using winter surveys. Hunters typically harvest adult does in disproportionate numbers to fawns, thus skewing the observed post-season recruitment ratio. To correct this, the number of does and fawns harvested must be added back to the estimates of doe and fawn numbers derived from a post-hunting-season survey.
Using sightings recorded in the stand by experienced hunters is an excellent method of estimating fawn recruitment – and other measures of QDM progress. In contrast to trail-camera surveys, observing deer from the stand provides an opportunity to observe behavioral cues that can help differentiate does from fawns as the season progresses. Even inexperienced hunters can quickly learn to differentiate adult does from fawns using educational tools, such as the selective antlerless harvest poster offered by the NDA. The only costs associated with using hunter observations as an index of recruitment are time spent in a stand and a quality set of optics, which you probably already own.
As with trail-camera surveys, timing of data collection is very important. Depending on when births occur in your area, and the timing of the hunting season, decreased fawn mobility may bias early season estimates to the low end. Observations recorded during the rut may bias recruitment high because fawns may be temporarily “abandoned” while estrous does are being tended by bucks, making these temporarily-orphaned fawns highly visible. As with trail-camera surveys, late-season hunts may overestimate recruitment as a result of doe harvest throughout the season. Therefore the choice time to collect observational data is during the fall, prior to the rut. However, as long as your data are sorted according to the period collected (early season, pre-breeding, rut, or post-rut), the data can be a very important tool for identifying year-to-year trends in recruitment.
It is important to keep in mind how a property is hunted when using hunter observations. Including data from an entire month you spent bowhunting a thick block of woods over a faint trail hoping for a shot at the buck of your dreams will definitely bias recruitment estimates because you will likely see the same does and fawns repeatedly, if you see many antlerless deer at all. Ideally large, infrequently hunted “nutrition plots” will provide the best picture of recruitment. Lightly hunted properties will typically see more fluctuations in recruitment than larger properties hunted by many simply due to smaller sample sizes – the more sightings in your dataset, the more precise the results. Frequently changing stand locations will improve the precision of your recruitment estimates as well as your hunting success.
Good estimates are the product of quality data. Hunter observation cards, sheets or booklets should be provided to every hunter, and the return of those records to a common area at the end of each hunt should be mandatory. At a minimum, records should include the date, hours hunted, stand location, hunter’s name, and the sex and age of each animal observed. If the hunter isn’t absolutely sure about the age or sex of an animal, it should be recorded as an “unknown.”
At the end of season, add up the fawns and does sighted during your ideal monitoring period, then divide the number of fawns by the number of does to get a fawns-per-doe index. As with trail-camera surveys, trends in fawns-per-doe are more important than the absolute value of recruitment for a particular year.
Hunters should also record the number of coyotes or other predators they see while hunting. At the end of the season, calculate coyotes seen per hour of hunting time, another useful index. If fawn recruitment is trending down while coyotes per hour is trending up, you don’t have to be a biologist to see the connection.
The simplest, but perhaps least sensitive, index of fawn recruitment is lactation rates. Lactation rate is expressed as the percentage of adult does (2½ and older) in a season’s harvest that were lactating, indicating that they raised at least one fawn successfully that year. Determining whether a harvested doe is lactating is as simple as noting the appearance of its udder, as the glandular tissue will be swollen and the teats enlarged. When field dressing, milk will be easily seen when the udder is cut. Simply note in your harvest data records whether each adult doe harvested is or is not lactating.
Timing is important when collecting lactation rates. In regions where the rut occurs in October and November, and fawns drop in May and June, lactation should be recorded for does harvested during October through early December. After this period, even does with fawns will likely have dried up. If fawns are born in July or later in your region, you may not want to begin recording lactation rates until October or later. This will provide sufficient time for does that may have lost their fawns to completely stop lactating.
Lactation rates of yearlings and does 2½ or older should not be pooled together. The percentage of all lactating yearling does is an important indicator of herd health, as these deer achieved sexual maturity and bred as fawns, but is not an accurate indicator of recruitment.
Unfortunately, lactation rates are not a sensitive index of recruitment as it is impossible to determine whether an adult doe without milk lost one, two or possibly even three fawns. In addition, it is impossible to know if a lactating doe was nursing one, two or three fawns. Therefore, lactation rates will certainly underestimate the level of fawn predation in your herd. Nevertheless, lactation rates can again provide important trend information if collected consistently from year to year, but should not be relied on as your only index of fawn recruitment.
As stewards of the deer resource, we should be proactive, rather than reactive, to these data. On properties with appropriate deer densities, low or declining recruitment rates should be met with more cautious doe harvest. In extreme cases, abstaining from doe harvest for a year to gauge the herd’s reaction may be necessary. However, adjustments in doe harvest must always be done in the context of the habitat. Responsible management requires deer densities above carrying capacity to be reduced to appropriate levels, regardless of predation.
The keys to successful herd monitoring efforts are consistency, consideration of deer biology, and good record keeping. One year of excellent, detailed record keeping will not make up for years of neglect. Collecting recruitment information using a variety of methods allows for comparison of results to ensure that a curious spike or dip in recruitment is a product of an actual change in recruitment, rather than a biased or erroneous dataset. Finally, the importance of using trends, rather than data from a single year, to make management decisions is critical. Studying the seasonal cycles in the biology of your local deer herd will not only improve the timing of data collection, but your abilities as a hunter as well.
About the Authors
Will Gulsby is a Ph.D. candidate studying wildlife ecology and management at the University of Georgia. His current research focuses on the impacts of coyotes on fawn recruitment. He is also a NDA member and enjoys hunting, trapping, and assisting landowners in improving their deer habitat and hunting experiences.
Dr. Karl V. Miller is a professor of wildlife ecology and management at the University of Georgia and a Charter Life Member of NDA. He is a previous winner of NDA’s Joe Hamilton Lifetime Achievement Award as well as NDA’s Al Brothers Professional Deer Manager of the Year Award.