Harrisburg — Once again, it all comes down to antlerless licenses.
Hunters, for decades, have been told that shooting more or fewer antlerless deer is the one best way to control deer populations across Pennsylvania.
The same is true, apparently, when it comes to fawns and predators. That was the message delivered at the Pennsylvania Game Commission’s most recent meeting.
The commission, together with researchers from Penn State, recently completed a fawn mortality study. Carried out between 2015 and 2017, it involved capturing whitetail fawns, putting collars on them, then monitoring how many survived.
In the cases of those that didn’t, researchers tried to figure out what killed them.
The results were almost identical to those from a similar study carried out in 2000 and 2001.
In that first study, crews captured 218 fawns: 110 in an agricultural area known as Penns Valley and 108 in the big woods setting of Quehanna Wild Area. In the latter study, researchers captured 165 fawns, 83 in Susquehannock State Forest, 82 in Bald Eagle and Rothrock state forests.
In the second study, researchers also looked at predator abundance and distribution.
Across the study areas, 40 to 50 percent of fawns survived to 34 weeks of age, which means they eluded not only mammalian predators, but hunters, too.
There was some variation.
In the Quehanna and Susquehannock study areas – both in the northern part of the state – 38 and 40 percent of fawns, respectively, survived to 34 weeks. In the Penns Valley and Bald Eagle/Rothrock study areas, survival was 53 and 51 percent, respectively.
Predators – black bears, coyotes and bobcats – were the leading cause of mortality in each area in the most recent study, Rosenberry said. Black bears take more fawns than the other two predator species, too.
That wasn’t surprising necessarily, Rosenberry said. All those species eat fawns when they can, Rosenberry said.
“They always have and they always will,” he said.
But deer adapt.
Researchers used trail cameras to estimate predator abundance and distribution. Bears often showed up in pictures captured in forest settings.
Fawns, though, most often showed up on cameras away from forests, in more open settings.
“These results show that deer can reduce predation risk to fawns by raising them in non-forested areas away from bears,” Rosenberry said. “As deer mature and predation risk drops, we see deer using forest sites more often.”
There are several real takeaways to get from all this, Rosenberry said.
One is that fawn survival has remained consistent over two studies done 15 years apart. Another is that most predator kills occur before hunting seasons get rolling, in most cases 10 weeks or more before they start.
Also, other research has shown that roughly 90 percent of adult deer survive from one year to the next, escaping not only predators, but hunters as well.
Armed with all that information, biologists consider predation when setting seasons and antlerless license allocations, he said. Fawn to doe ratios in the hunter harvest are calculated, too.
“If predators take more fawns, fawn-to-doe ratios should decline,” he said.
That hasn’t happened, he added.
Neither are deer populations declining. Four of the state’s 23 wildlife management units have stable deer populations; in the other four, populations are increasing, Rosenberry said.
If that changes, though, doe licenses are the key to setting things right, he added.
Simply killing more predators is neither popular nor effective, depending on the species, he noted.
Black bears are the number one killer of fawns in Pennsylvania, Rosenberry noted, yet “most deer hunters do not support reducing bear populations to increase deer numbers.”
They would be OK with reducing coyote numbers, but the hunting season on them is already 365 days long, with hunting allowed 24 hours a day, seven days a week. And still coyotes are thriving.
“These two examples demonstrate the social and biological challenges associated with attempting to control predators for the benefit of deer populations,” Rosenberry said.
“Fortunately, there is one wildlife management action that can be effective should predator impacts become too high – adjustment of antlerless deer hunting opportunities.”
Limiting hunters to killing fewer antlerless deer would – even in areas with high predator populations – allow deer herds to increase, he said. The commission proved that before.
If deer numbers drop below objectives any time in the future, limiting antlerless hunting would again be the way to address the situation, he said.
Predators or no predators.
“Based on field data from Pennsylvania, there is no need to create new programs or initiatives in an attempt to alter the predator-deer relationship. Pennsylvania’s deer populations are sustainable with existing predator impacts and existing programs can be adjusted if needed,” Rosenberry said.