What whitetail fawn studies tell us about deer predation, paternity

Whitetail fawns usually hit the ground in May here in the Northeast and the Midwest, but depending upon the timing of the rut, or peak breeding time in the previous fall, we may catch glimpses of the bulk of them either early in the month or as late as Memorial Day.

And because last season's rut for northern whitetails occurred in early November, it followed that the majority of our fawns made their corresponding appearance in mid-May, after the requisite 200-day gestation period.

New technology and corresponding research into whitetail behavior has greatly challenged some of the older and longhand deer behavior beliefs.

And one area of this new knowledge brings up some interesting facts of the causes of fawn mortality.

From a game management perspective, results from these new DNA and VIT (Vaginal Implant Transmitter) studies have illuminated whitetail herd dynamics and breeding success (recruitment).

So game managers, whether those working for government, private consultants, or hyper-local hunter/managers, and those of us interested in wildlife can gain knowledge about the front end of our whitetail population.

Tiny VIT’s are placed in doe after the rut and are expelled when that doe gives birth. These radio transmitters are coupled with a temperature sensor that emits a different beep pattern from when the VIT is in place, inside the doe and signals when the fawn is born. Temperature differences are immediately detected and recorded, signaling exactly when a doe has given birth, allowing researchers to immediately move to the birth site and locate the fawn and record more data.

From these fawn birthing studies (especially with blood samples and new DNA research), it has been determined that there is a much higher percentage of multiple paternity in twins and triplet fawns than previously thought.

That means, those twin fawns we see may very well have different fathers.

The long-held and in some quarters cherished image of the big-racked buck that rules a harem and has exclusive breeding rights, due to his superior fighting equipment and size, has been shown to be exaggerated and not the real world of the whitetail, after all.

Multiple paternities appear to be especially true in whitetail populations where a high percentage of bucks equal greater breeding competition.

Doe are actually bred by different bucks during the same estrus cycle. One case that was cited produced triplets by three different sires, each of which was different age class bucks!

Another compelling finding through the new research is that yearling doe and 1.5-year-old doe usually produced only one fawn.

Doe that are 2.5-years-old and up generally birth twins or triplets.

So, as a practical matter for game managers, and as stewards of our local deer herds, hunters should perhaps reconsider shooting the "big doe" if we want to increase the whitetail population.

Let the big doe walk and tag a smaller one instead as it would have less effect on fawn recruitment.

And conversely, if game managers want to trim the herd, then by all means, hunters should take out big doe, older doe. Doe over 2.5-years-old and up recruit (birth) 2.3 fawns per year, while younger does are at .7 per year, according to researchers.

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Fawn predation and mortality is also being scrutinized as never before, and a recent study by the Pennsylvania Game Commission has concluded that predators killed 23% of fawns.

Of the 49 fawns in that PGC study, coyotes killed 18. Sixteen other fawns were killed by black bears and three by bobcats.

The relatively high incidence of bear predation on fawns was corroborated by a second Pa. study.

In another Pa. study, predation accounted for 46.2% of 106 whitetail fawn mortalities through 34 weeks. The researchers attributed 32.7% and 36.7% of 49 predation events to black bears and coyotes, respectively, which correlates closely with the other Pennsylvania study. Natural causes, excluding predation, accounted for the other mortalities.

In a University of Auburn study, only 3 of 14 fawns survived, with three types of mortality found: coyotes, bobcats, and abandonment.

Now granted, that's a small sample, hard to hang your hat on it. But coupled with two other Southeastern studies:

Coyotes potentially caused up to 63% of mortalities in white-tailed deer fawns in an Alabama population (Saalfeld and Ditchkoff 2007) and 80% of mortalities in a South Carolina population of whitetails (Kilgo unpublished data).

One can argue the numbers, but these and other new studies seem to correlate and agree that predation on fawns by coyotes and black bears can put a significant dent in a local whitetail population, much greater than had been previously thought.

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But what can we do to increase fawn survival, besides hunt and trap predators?

Research, along with commonsense, tells us that a fawn is most at risk during its first weeks after touchdown.

Its chances of survival increase and keep going up each day it lives. Fawns that hide best live longest. Researchers conclude that poor bedding cover (lack of undergrowth) adds to fawn mortality.

Further, fawn predation is highest where there is a lack of bedding cover, such as in many suburban landscapes, parks, and older growth forest areas with a high canopy and sparse vegetative cover.

Ideal fawning areas should be as dense as possible, a mixture of weeds, flowers, brush, etc. scattered throughout a property to give whitetail fawns a greater chance and predators a greater challenge.

— Oak Duke writes a weekly column.