Research: Fawns born in city have better chance of surviving

BLOOMINGTON, Ind. (AP) - City living agrees with young deer, according to research from Ball State University.

"The basic bottom line is the fawns in town have twice the survival rate of fawns outside of town," said Tim Carter, a biology professor at Ball State who is helping with research of fawns and adult deer in and around Bloomington. That's what Carter and other Ball State researchers have discovered after conducting a 2013 to 2014 study of fawns in Bloomington and also in surrounding rural areas.

In all, 119 fawns were caught and fitted with radio collars to track their movements during their first year. In 2015, the results from those two years of field study were analyzed using a special modeling software program. The program allowed researchers to put the deer into either an urban or rural category and then, using statistics for the density of people in that area, determine how many of the fawns would survive. The results show that rural fawns had a 40 percent chance of surviving their first six months of life. In Bloomington, urban fawns had an 80 percent chance of surviving their first six months.

Carter believes one reason the "in-town deer" as he refers to them, were twice as likely to survive was that they were living in close proximity to people. Coyotes were responsible for the majority of fawn deaths in the rural areas of Monroe and Brown counties. In Bloomington, collisions with vehicles killed the most fawns. Carter said that although there are coyotes in Bloomington, he believes there are fewer than in rural areas, and that since many fawns were located inside fenced areas, coyotes couldn't access them, keeping them safe from their number one predator.

"Life is really good in town for these deer, and when you have more deer surviving, you have more deer," Carter said. "That leads to growth in the population quite quickly."

Carter said the percentage of fawns that survive is more important than the actual number of deer that survived. The survival rate can vary widely from year to year.

"Survival in deer is a very dynamic thing," he said. "One year, you might have only 5 or 10 percent survival, and then the next year, you can have 80 percent survival."

Carter said the study of fawns allows the researchers to look at the effects of urbanization on the deer population. He also said Ball State's research was not in any way connected with the Griffy Lake Nature Preserve deer project, in which city officials decided to allow a cull of deer. The 2014 cull was called off after there were insufficient deer recorded at each of the bait sites set up within the preserve.

"There are many reasons that the Griffy thing didn't work," Carter said. One major factor was the quantity of acorns available for deer to eat last year, he said, which meant the deer weren't hungry enough to be attracted to the bait. "You just couldn't get deer to do anything you wanted."

Ball State researchers are entering their second year of studying adult deer in Bloomington and surrounding rural areas. Carter said they also had trouble last year catching deer because there were so many acorns available. The researchers often use apples and peanut butter to lure deer to their traps.

It took researchers two months before they caught their first adult deer in Bloomington, Carter said. "It's because they just wouldn't come to bait. They just weren't interested." It was only after the acorn crop was gone that deer were attracted to the Ball State bait piles, he said.

Ball State researchers are now setting out more bait piles in an effort to trap and collar more adult deer both inside the Bloomington city limits and in the country. Four methods are used to catch the deer: clover traps, which are pens that the deer enter to eat; drop nets that are suspended over the ground and drop on the animal; suspended net guns that hang from a tree with a bait pile underneath and shoot a net over deer when they are feeding; and dart projectors that a person in a tree-stand shoot into the deer that they then track. In all four scenarios, the animals are given a tranquilizer that knocks them unconscious while researchers work on them.

Carter said the tranquilizer is safe for the animals and that researchers monitor the deers' heart rate, respiration and temperature while they are under. Once the tranquilizer wears off, the deer are up and moving in five to seven minutes, he said. Since the deer are then tracked, the researchers are able to monitor them to make sure they are OK.

Studying the adult deer will help the researchers determine if the deer are moving between rural and urban areas or whether they are staying mainly in one or the other. It's now clear that deer in town have higher reproductive success and that more of the fawns are surviving. That means the urban population is expanding more rapidly, but Carter said researchers now need to find out if the deer will move out of the city.

"Population size: It's all about input and output," Carter said. If Bloomington wants to again consider controlling the deer population, Carter believes the research will help city officials be able to choose the method that will work best.

"There are a whole bunch of methods, from lethal control to birth control," Carter said. "We have to have all the information before deciding what is best to control the population."

That information includes evaluating survival rates, which the fawn study has done. Now it's time to determine the movement of the deer.

"Do they move in and out of town or do they stay put?" Carter said. "Once we understand that population dynamic, we can understand which of these methods will be the most appropriate."


Source: The (Bloomington) Herald-Times,


Information from: The Herald Times,

A deer grazes in a yard along a major city street in Bloomington, Ind. Aug. 17, 2010. Ball State University researchers have concluded that fawns living in the city have twice the survival rate as those in rural areas after a two-year study in Bloomington, Ind. (David Snodgress/Bloomington Herald-Times via AP) The Associated Press
Two fawns graze in a yard in Bloomington, Ind. Aug. 17, 2010. Ball State University researchers have concluded that fawns living in the city have twice the survival rate as those in rural areas after a two-year study in Bloomington, Ind. (David Snodgress/Bloomington Herald-Times via AP) The Associated Press
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