Do only top-ranking bucks breed does?
For decades, people believed the white-tailed deer mating system was a dominance-based breeding hierarchy. In other words, most offspring were sired by a few dominant males. For white-tailed deer, this meant – or at least we presumed – the top-ranking buck (based on physical traits like age, body mass, and antler size) had breeding rights to any and all females he encountered. No questions asked.
Behavioral observations set the stage for this theory of the whitetail mating system. But what happens when we aren’t watching? Thanks to genetic technology, we now realize that we only read the first chapter on white-tailed deer breeding ecology.
Multiple Paternity in White-tailed Deer
In 2002, the next chapter was revealed. That’s when an article in the Journal of Mammalogy was published titled “Multiple Paternity in White-tailed Deer Revealed by DNA Microsatellites.” This paper documented multiple paternity in captive white-tailed deer. In litters of two or more fawns, 26 percent of them had different fathers.
This discovery raised the bigger question: does multiple paternity – and female promiscuity – occur in wild, free-ranging deer populations? The answer came two years later. In 2004, the first case of multiple paternity in free-ranging white-tailed deer was documented in Michigan (Journal of Mammalogy, “Paternity Assignment for White-tailed Deer: Mating Across Age Classes and Multiple Paternity”). Here, 22 percent of litters with two or more fawns had different fathers.
This research also showed the oldest males did not monopolize breeding; thus, shattering the belief that a few dominant males do all breeding. Since this initial finding, multiple paternity has been documented in every free-ranging white-tailed deer population that has been tested.
Twenty to twenty-five percent of all those twins out there are only that in the most basic sense of the word- two offspring produced from a single pregnancy.
Interesting Fawn Data
Most does birth two fawns in the spring. Triplets have been documented but are far less common.
From past embryo counts in Pennsylvania:
Two-year-old does: 34% carried a single embryo, 64% carried twins, and 3% carried triplets
Adult does (> 3 years old): 22% carried a single embryo, 73% carried twins, and 5% carried triplets.
By: J.T. Fleegle
Wildlife Biologist, Deer & Elk Management Section
Pennsylvania Game Commission