When Doe Fawns Breed, It’s a Good Sign

buck_tending_young_doe_qdma_574_471_sSome doe fawns breed and conceive in their first fall, at around six to eight months of age. The percentage that do this is determined by nutrition – they attain sexual maturity if they reach a specific weight threshold. In general, southern fawns reach it at approximately 70 pounds and northern fawns at approximately 80 pounds live weight. Fawns that manage to hit this threshold in their first fall tend to do so late, in December or January, and they are one reason for an apparent “second” rut in many areas.

Since the percentage of doe fawns that breed is based on weight, not necessarily age, it is a good indicator of herd health, and you can monitor this index by checking the lactation status of any yearling does that are harvested. If you kill a doe this fall that is 1½ years old by the jawbone and has milk in its udder, it was bred as a fawn.

Deer herds with access to abundant high-quality forage and light to moderate winters can have breeding in more than 50 percent of their doe fawns. Conversely, deer herds exposed to poor habitat or severe winters often have less than 5 percent of their doe fawns reach the threshold weight and breed.

Doe fawn breeding rates vary widely across states. A 2010 QDMA survey showed less than 10 percent of doe fawns bred in Delaware, Idaho and South Carolina, while 70 percent of them bred in Iowa. This is testament to the mineral-rich soils and volume of agriculture in Iowa that provides abundant high-quality forage and allows fawns to grow rapidly. Amazingly, an estimated 10 percent of the doe fawns that bred in Iowa gave birth to twins. Even more amazing is that 21 percent of the doe fawns that bred in the farmland region of Ohio had twins!

Nationwide, an estimated 26 percent of doe fawns bred in 1998, and that average dropped slightly to 23 percent in 2008. However, since this index is so closely tied to a region’s habitat quality, it is difficult to lump the breeding rates across a region or even a state together. For example, in Pennsylvania an average of 25 percent of the doe fawns bred in 2008, but that percentage varied from 0 to 38 percent across the state’s wildlife management units (WMUs). Similar ranges occurred in Alabama (0 to 33 percent), New Hampshire (0 to 25 percent), South Dakota (0 to 58 percent), and Virginia (3 to 49 percent). These rates likely varied even more across specific properties within any WMU. This is one reason why collecting data from your location and using that to make site-specific harvest recommendations can benefit your Quality Deer Management program. Also, you can compare your data to WMU or state averages and assess how your QDM program measures up, and whether you have realistic expectations for what you can accomplish.

QDMA is the only conservation organization that monitors whitetail populations and herd health. Help us do more to track, encourage and protect whitetails: please become a QDMA member today. Your support is needed and appreciated!

  • rational_atheist

    My experience is in populations where carrying capacity is almost entirely driven by winter severity. In such cases, the resources during the growing season, for any individual animal, are essentially unlimited. Most animals, except for fawns and dominant bucks, go into the winter in relatively good health.

    Under such conditions, fawns will almost never (successfully) be bred. The only exception would be cases where the number of yearling does and older is very small. As you know, unbred adult females shed pheromones which encourage the males to retain rutting behaviour and focus and which suppress oestrus in fawns. If all the females are bred at the first oestrus, the lack of receptivity pheromones may allow some fawns to enter oestrus a month or two later. In such cases, though, testosterone levels in the pool of males will be beginning to decline and the relatively weak receptivity signal emitted by fawns will be insufficient to garner much breeding activity.

    Finally, a fawn impregnated in the fall still has to make it to fawning season the next spring. Given that Kw-mediated populations, such as the ones in my area, show the highest mortality rates among fawns, born and unborn (Verme fawn losses (all females) sometimes exceeding 70%), a pregnant fawn is not likely to be able to carry her offspring through to May of the next Spring. In my area, if I were to see substantial numbers of wet yearling does in the harvest, I’d be concerned about the buck:doe ratio since there are, clearly, insufficient does in the population.

    Rather than celebrate such a condition, as this article seems to encourage, I would be inclined, at least temporarily, to protect does during the hunt, even if it were to result in the harvest of more bucks. Ideally, females should not be breeding to an appreciable extent before they’re yearlings. Fawns are not effective breeders and a population which depends, in any measure, on reproduction by fawns is not particularly resilient.

    From the Conclusions section of a recent paper: “We found that fawn reproduction… [is] …highly variable and is
    likely dependent on the interaction between available habitat, deer
    density, and resource availability which influence fawn growth and fat accretion that, in turn, influence estrus onset.”(1) As I said, after decades of on-the-ground management experience, I would move density to the top of the list of determinative factors and not solely for the resource-partitioning parts of the equation.


About Kip Adams

Kip Adams of Knoxville, Pennsylvania, is a certified wildlife biologist and QDMA’s Director of Conservation. He has a bachelor’s degree in wildlife and fisheries science from Penn State University and a master’s in wildlife from the University of New Hampshire. He’s also a certified taxidermist. Before joining QDMA, Kip was the deer and bear biologist for the New Hampshire Fish & Game Department. Kip and his wife Amy have a daughter, Katie, and a son, Bo.