Since a healthy doe can give birth to twins or triplets, it’s no surprise that every spring’s fawn crop boosts the deer population numbers.

But how many of those spotted youngsters survive to maturity?

Pennsylvania has conducted two studies of fawn survival (2000-2001 and 2015-2017) and the statistics are emerging. To begin the Pennsylvania study, researchers first looked at data from 30 other studies from the United States and Canada. Tess Gingery, who recently completed her M.S. in Wildlife and Fisheries Science, searched that research for patterns.

Concurrently, Asia Murphy (Ph.D. in Ecology) collected images from hundreds of game cameras over a two-year period, to find out how many predators and deer were in an area. Other scientists looked to see if they could define a pattern between predators and fawns, dependent on features of their home ranges – such as deer density and quality food sources.

Before launching the study, researchers surmised that high densities of deer would mean less food for each, with poorer nutrition leaving the fawns more susceptible to predation. But after studying 29 different locations in the United States, including 4 in Pennsylvania, researchers found that there was no relationship between the density of a deer population and the rate of fawn survival.

What about features of the deer range, such as agricultural fields and understory vegetation? Researchers found that landscapes with more agricultural land cover are associated with great fawn survival.

Perhaps the biggest question to answer – which animal kills the most fawns? To determine cause of death involves a bit of Crime Scene Investigation.

“Determining if a fawn was killed by a car is pretty easy,” Gingery said. “Determining who snacked upon a fawn, not so much.”

“Piecing together information from the necropsy – size of bite wounds, distance between bites and location of bites is put together with field investigation of tracks, scat, hair…..and the killer is named,” she added. “But despite all these tools there is one very large dilemma – determining the difference between a fawn killed by a coyote versus a domestic dog.”

“This is noted as an uncertainty in many studies – some list the number of fawns that died from coyotes and discussed how domestic dogs could have been responsible for a portion of those deaths, while others make no attempt to differentiate at all,” Gingery explained. “Since both coyotes and domestic dogs are from the same family, it’s easier and accurate to report the number of fawn deaths attributed to canids.”

Of the “Big Three” fawn killers (black bears, canid species and bobcats), canids took first place. Additionally, research showed that the proportion of fawns that died from canid predation was similar in various landscape types (open agricultural fields, woods, mixed habitat).

Researchers are still compiling data. They are working cooperatively with researchers hailing from the Pennsylvania Cooperative Fish and Wildlife Research Unit, the Penn State College of Agricultural Science.

So, what have researchers learned? Deer density doesn’t affect fawn survival. Landscapes with greater agricultural land cover have higher fawn survival. Predation is the leading cause of fawn mortality in all landscapes. Canids are the leading predator of fawns.

“But what does this mean for deer in Pennsylvania?” Gingery asked. “Stay tuned.”