The scenes described of Indiana farmlands and elsewhere seem like they leapt from a page in a horror novel, with black vultures descending into the forests and pastures of the Midwest and beyond.

Farmers tell of ferocious attacks on their animals: wakes of funereal, hunch-shouldered large black birds feasting on newborn calves as they emerge from their mothers, and sometimes preying on the mothers themselves.

“The last couple of years they have gotten really aggressive,” said John Hardin, a livestock producer in Scott County in southern Indiana, about 20 miles north of Louisville, Ky., who often sees eight to 10 of the birds on his farm. At least two of his calves have been killed by vultures, perhaps more. “They like the navel area and they will take it all the way down to the bone and hide.”

Vultures are often called “nature’s garbage disposals” because their highly adapted digestive and immune systems enable them to eat dead and diseased animal carcasses with impunity. While scavenging is considered a critical ecosystem service, reports of black vultures preying on live animals are relatively unheard-of, some experts say, and some expressed skepticism that predation is actually taking place.

The situation in Indiana this summer proved alarming enough that farmers are now allowed to quickly obtain permits — acquired from the U.S. Fish and Wildlife Service by the Indiana Farm Bureau — to “take,” or kill, up to three birds, a program newly in force in other states in the Midwest.

“These migratory birds are coming across the Ohio River,” said Greg Slipher, a livestock specialist with the Indiana Farm Bureau. “I got a heads up from my counterpart in Kentucky, and he said, ‘They are coming your way’ and he was right. Over the last three or four years, we have gone from a few reported incidents to many.”

A great deal remains unknown about the bird and why its numbers are growing in states where they were unseen a decade ago. They were traditionally found in the southern United States and Central and South America, and it is unclear why they have significantly expanded their range northward and into the West. Some speculate milder winters because of climate change may be a factor.

From 2007 to 2019, breeding populations of black vultures increased at rates of one percent to four percent annually across the entire range of the species in the United States, with the exception of small portions of the Gulf Coast and south Central Florida, according to an analysis of eBird data by the Cornell Lab of Ornithology.

The scope of predation by black vultures is far from settled as they have moved into new territory. One of the country’s leading ornithologists is highly skeptical and expressed concerns about permits granted to kill them. Black vultures are one of 1,100 or so species protected under the century-old international Migratory Bird Treaty Act; harming them without permits can result in stiff fines or even jail time.

“I am going to take an extreme position here and say they don’t kill healthy calves,” said John W. Fitzpatrick, the recently retired director of the Cornell Lab of Ornithology in Ithaca, New York.

For seven years he managed the Archbold Biological Station in Central Florida, which includes a working cattle ranch where black vultures were present. “They are often seen around calves in trouble that are stillborn or dying and they jump in on them quickly,” he said. But, he added, “the idea that they are predatory on livestock is false.”

“In my view it should be considered lore because it’s not well documented,” he said. The vultures may occasionally attack a healthy calf, he said. But, “are we really talking about something that is so pervasive and economically destructive that we need to start permitting the destruction of a protected bird?”

The vultures are big birds, weighing nearly five pounds, topped with what looks like a helmet of gray, featherless skin. They have a large span of wings up to five feet, which provides loft as they soar on thermals and spot prey. They are one of three species of vulture in the U.S.; the turkey vulture and the endangered California condor are the other two.

“The black vulture is an amazing bird,” Dr. Fitzpatrick said. “They are faithfully paired, have amazing and complex social behavior, and are super smart. They closely guard the nest. The eggs hatch and become these fuzzy white chicks, and for a month or six weeks, you can always figure out there is a nest nearby because one of them is sitting day after day, week after week, in the same spot.”

Dr. Grant Burcham is a veterinary diagnostician at the Heeke Animal Disease Diagnostic Laboratory at Purdue University, which maintains a research cattle farm.

Dr. Burcham said that he received a calf killed by vultures and euthanized two others that were attacked. Autopsies showed the calves were not healthy — two had “scours,” an intestinal illness, and the third a broken leg — and may have been selected by vultures who sensed their vulnerability. “The animals were dehydrated and would have been visibly slow, and that’s why they were targeted presumably.”

A recent paper concluded that the incidence of predation by scavenger birds in Argentina, including the black vulture, though perceived to be frequent, was not common at all.

Patrick Zollner, a professor of ecology at Purdue University, agreed that empirical evidence of predation was lacking. “What is totally unknown in Indiana and most places is how often this happens,” he wrote in an email. “Addressing that gap is one of the goals of our ongoing research.”

Marian Wahl, a doctoral student with Dr. Zollner at Purdue, who is studying the birds in Indiana, said she believed black vultures number several million in the United States, and in Indiana have increased from just a few a couple of decades ago to about 17,000 now.

While the U.S. Fish and Wildlife Service can issue special permits to kill birds causing damage, the process to obtain them can be lengthy and cumbersome and cost $100 each. The relatively new program in Indiana and elsewhere allows state farm bureaus to obtain a large number of permits and issue sub-permits, which experts say is more responsive.

Mr. Slipher said he has received 45 requests for “take” permits and has authorized 22 since the program went into effect in early August.

While the permits allow each person to shoot three birds, Mr. Slipher says there is a better strategy.

“I am advising, don’t go out there and shoot all three the first day,” he said. “One of the things we know about this particular species is that they react substantially to effigies of their own like. We are encouraging our producers to shoot that first bird and hang that bird in effigy.”

It’s an approach that has helped the hardest-hit producers in Kentucky — somewhat. Although real and false hanging effigies are widely used to disperse the birds, and there are studies that show they work, the effectiveness is not well understood.

“If you use an effigy to disperse a roost, does that keep them away from livestock or do they just move to a roost down the road and keep going back to the same farm?” Ms. Wahl asked.

Joe Cain, of the Kentucky Farm Bureau, said the black vultures began appearing in his state in the early 2000s, and that by 2015, Kentucky had begun the new permitting system just instituted in Indiana.

“We’re only hitting the hot spots,” Mr. Cain said. “The ones having the most severe problems are the ones who call us. There’s a lot more out there seeing depredation, but at least they know there’s a program out there to help them protect their livestock.”

The permits have not significantly reduced the numbers of cattle killed, officials said. In Kentucky, about 500 to 600 cows a year have been killed, they noted, adding that more lambs, kid goats, free-range chickens and turkeys have been felled as vulture populations increase.

Other tactics include making loud noises with devices such as propane cannons, firing pyrotechnics, squirting the birds with high-pressure hoses and using guard dogs. Because the vultures often roost in large dead trees to survey the landscape and look for prey, cutting down those trees can also provide relief. The efficacy of these measures is part of the study that Ms. Wahl and Dr. Zollner have undertaken.

Mr. Cain would like to see federal law changed to help farmers. “We’ve asked Congress for a safe harbor provision,” he said. “If they see depredation occurring, it’s unreasonable to say, ‘I am going to go back home and get a permit application and wait two days and get the permit.’ When they see it occurring, it makes a whole lot more sense to protect your livestock then.”

The attack of a vulture on live prey is a grim scenario, farmers say. “The birds zero in during birth — essentially at the most vulnerable moment,” Mr. Slipher said. “Literally as the calf is on the way out of its mother we’re getting black vultures attacking the calf and attacking the mother.”

The bird often picks out the eyes, the nose, mouth and navel. Farmers say each animal that dies is valued at $1,000.

They are a nuisance for other reasons, too: They tear asphalt shingles off houses, rip off windshield wipers and rubber seals around vehicle sunroofs, and tear up seat covers on farm equipment and boats.

Their stomach acid is nearly as corrosive as battery acid, and their droppings, urine and vomit can eat away at roofs, towers and others places where they roost.

But vultures are also a proven and critical part of the ecosystem. Massive die-offs of vultures took place in India, for example, because of widespread use of a veterinary drug toxic to the birds. That led to an increase in rabies. Vultures used to clean up dead cattle and other waste; when they disappeared, dogs began feeding off the waste, and as their numbers increased, so did the incidence of rabies.