Photo by iStock September 10, 2018
Prof. Jake Bowman reflects on 17 years of deer research at UD
When Jake Bowman came to the University of Delaware 17 years ago after getting his doctorate from Mississippi State University, he encountered a problem with regards to deer research that he had never experienced before. Not only did some of the people he talked to have no idea about the number of deer in the area, some of them even thought that the animals were endangered.
“That was kind of like a ‘Wow’ moment for me. I’m at a place where people don’t realize that deer are as abundant as they were in colonial times so it was kind of like, we need to do some things [to raise awareness],” said Bowman, chair for the Department of Entomology and Wildlife Ecology in UD’s College of Agriculture and Natural Resources.
Bowman and his students have done a variety of work on deer over the years from assessing crop damage, the success and failures of controlled hunts, birthing rates and looking at Sika deer populations.
The first study he ran at UD took place at Chesapeake Farms and was in conjunction with North Carolina State University.
The study lasted for two years and looked at the timing of fawning as well as cover crops, trying out a variety of clovers that could be used as a lure crop for growers to attract deer and reduce crop damage — discovering that crimson clover was the one the deer seemed to go to the most.
Finding that cover crop was important for growers because even when deer are at a moderately balanced population, they can still cause problems for agricultural producers.
“Soybean and wheat are so nutritious that it’s better for the deer to eat those crops than it is to eat the native forage,” Bowman said. “They’re not going to walk around the woods and eat stuff when they’ve got soybeans right there so they can cause issues.”
Two other studies looked at exactly how deer cause issues with regards to soybean and wheat crops. The studies took place over five years and were conducted on a grower’s farm around the Dover area.
Bowman said the results were interesting, showing that even at a density of 60 deer per square mile — which is about average for this area — sometimes deer browsing increased soybean yield.
“Generally, it was more positive than negative and that’s because when deer browse on soybeans, it makes them bushier and at the nodes of those is where the bean is produced,” said Bowman.
The biggest finding of the study was that at a field’s edge, what looks like deer damage is actually just the naturally occurring edge effect from the forest.
“When you’re on the edge of a field,” Bowman said, “you’re going to have shade, you’re going to have trees drawing nutrients, it’s all the things that are impacted by the forest edge because we did all of this right on the forest edge to look at the impact and we did not see that it was caused by deer. The effect of deer and the effect of edge were independent of each other.”
The soybean study was replicated in Mississippi with similar results.
The companion study that looked at wheat also found that while deer did eat wheat, they didn’t cause enough damage to impact yield and while Bowman isn’t saying that deer don’t cause crop damage — which they certainly do — they aren’t as big of culprits as some people might think.
“When someone sees a deer standing in a field, they automatically think there’s deer damage and it may not be the case,” said Bowman. “Deer are getting blamed for a lot when they may not necessarily be having a huge impact. There are certainly farms that have higher deer numbers that have impacts on soybeans and I’m definitely not trying to say that they don’t have any damage but the average level of browsing that we see within the state is not reducing yield.”
Bowman also led a study at Fair Hill that lasted three years and looked at the impact of controlled hunts on deer populations and how Fair Hill officials might be able to better manage the deer population.
“They were not happy with the numbers and the numbers were high,” Bowman said. “It was around 120 deer per square mile.”
The research showed that the deer were quickly moving into areas where the hunters weren’t allowed to hunt, such as around horse barns and residences.
“Within the first day or so, they’d pile into those areas so if you continued to hunt for a couple of days, towards the end of that hunt, you weren’t seeing any more deer,” said Bowman. “We also found that they quickly returned to those areas after a break of a few days. Our recommendation was to shorten the hunts to maybe one day hunts that are a week or two apart so that you can have a much greater impact and then to know where those refuge areas are and try to figure out how to deal with those pieces.”
There were also deer that lived in the areas around the horse barns that would never come out and not be available for harvest.
Looking at those kinds of questions led the research group into another study where they looked at Delaware’s safety zones, where a firearm can’t be discharged within a certain distance of an occupied residence.
“I digitized all the structures in New Castle County and then put a 200-meter buffer around it and overlaid that on deer habitat and figured out that almost none of the deer habitat was available for hunting by the current regulations,” Bowman said. “By having that safety zone, you were handicapping it to where you couldn’t control deer numbers.”
In Delaware, a bow is considered a firearm, so archery hunters were also not allowed within 200 meters of those areas.
“This study allowed the state to use that information to change the regulations so now it’s 50 yards for archery hunting,” Bowman said. “That allows landowners with smaller parcels to manage their deer a little bit more properly.”
With regards to all of the deer research, Bowman said that it would not be possible without the cooperation of landowners and hunters.
To help study the deer populations over the years, Bowman has employed a number of graduate students who have an intense research commitment given the nature of studying deer.
For projects where the deer must be captured and radio collared, Bowman said that students usually spend an entire season — from when classes end in December through the following August — living in the field.
“It’s pretty intense,” Bowman said. “They’re out all the time. They get to know landowners which helps us a lot too. It’s definitely an intense period. For us, it’s a challenge because we’re trying to find housing for long periods of time.”