Black vultures have been expanding their range into southern Indiana over the last decade, sometimes targeting and killing newborn calves.
Now researchers at Purdue University along with experts with the U.S. Fish and WIldlife Service are trying to understand the scale of the problem - and what can be done about it.
In an open field in Dubois County in southern Indiana, researcher Marian Wahl dragged the carcass of a stillborn calf off of her truck and into a patch of flattened grass.
“I feel slightly morbid but scientifically important is the entire research project I’ve got going on here,” said Wahl.
Not long after she placed the calf’s body within a ring of cameras that snap photos of any black vultures that land there, Wahl spotted them rising up from trees on the edge of the field.
“We’ve got a little bit of a vulture restaurant set up here,” she said. “There was a calf here yesterday and so they are just swinging by again today to see if the restaurant is running again today.”
Wahl’s admittedly grim research involves comparing calves attacked before death and those attacked after their death. It’s part of an effort to determine just how many calves black vultures are killing.
“We have essentially no idea how much of a problem this is in Indiana,” she said. “We know for certain that it is happening here, but we don’t know how often it’s happening, how many attacks may be attributed to black vultures that aren’t black vultures and on the flip side of that how much damage is due to black vultures that we’re completely missing out on.”
Black vulture populations have been increasing in southern Indiana since the 1990s, with populations peaking somewhere at about 11,000 as of 2018. Experts are not entirely sure why but have pointed to things such as climate change or population growth that have pushed vultures to look for new places to roost.
What is known is that black vultures have been expanding their range northwards, presenting new problems for farmers.
Jason Tower is the Farm Superintendent at the Southern Indiana Purdue Agriculture Center. Cattle, sheep, and goats graze at the center and Tower says black vultures have become a problem during calving season in the fall.
“It’s frustrating as a livestock manager to see all the work you’ve done to get an animal born to have mother nature come and kick you in the butt,” he said.
Tower said he’s personally had some half-dozen calves in his herd attacked and killed by black vultures. During calving season, he said he may go out as many as five or six times a day to try and scare black vultures away from his herd.
“We’ll make noise. Gunshot blasts in the area, bottle rockets, that kind of stuff,” he said.
And, Tower said, that kind of time-intensive effort isn’t something available to every livestock farmer.
“It adds something to your day,” he said. “I’m fortunate that I’m able to manage cattle on a full time basis. I’m here all day long. Most producers in Indiana, the cattle is a secondary business.”
Black vultures are protected under the Migratory Bird Treaty Act, meaning that in order to use lethal force farmers will need to get a permit from the federal government.
Officials with the U.S. Fish and Wildlife Service say the process takes a couple of days and they have never denied a permit to farmers who have experienced livestock losses, but farmers like Tower say they’d like to see that process streamlined.
Lee Humberg is the state Director for the USDA APHIS wildlife services in Indiana. He said it’s important for researchers to get an understanding of how many calves are being killed to determine the best way to manage the black vultures.
“It’s always a balancing act,” Humberg said. “How do we provide tools and techniques that are going to keep the most people happy and impact the wildlife as minimally as possible?”
Humberg said because there isn’t a lot of good data about black vultures and how they’re behaving in Indiana, it’s important to exercise caution.
“Being too aggressive could have negative implications down the road in terms of their overall population,” he said.
Managing vultures is important, researchers say, because of the balance they provide to an ecosystem.
Marian Wahl points to places like India that have seen declining vulture populations.
“In India they’ve lost 99% of vulture species. They’ve had huge increases in rats and feral dogs, rabies and tuberculosis,” she said. “So having a healthy vulture population is really really important. Having these birds here is a good thing so long as we can protect farmers and cattle.”
Once Wahl gets a handle on the scale of the problem she says she’ll start to look at the most effective methods for deterring black vultures, which could include tracking their location.
“We know a lot of the non-lethal techniques are really effective at making the birds leave a particular roost but we don’t know if that changes any of their foraging behavior or not,” she said. “Having these GPS transmitters on we can see whether these non-lethal controls actually move them away from the farm or whether they just move them two miles down the road and don’t actually change anything.”
In the meantime, farmers like Tower say they just want to know how best to protect their herds.
Farmers can find a link to a survey Marian Wahl is conducting on black vulture interactions here.
You can contact Ben at bthorp@purdue.edu or follow him at @sad_radio_lad.