On the lush, rolling savannas that link northern Tanzania to Amboseli National Park in Kenya, foraging elephants move back and forth on a sloping landscape in the shadow of snow-capped Mount Kilimanjaro.

The animals are accustomed to open-sided 4x4s full of tourists on the Kenyan side and seem to sense no danger from the visitors pointing phones. But what the animals probably do not know is that just across the border on the Tanzanian side, which for three decades was just as safe as the park, there are now people pointing guns, not cameras.

Since September, five bull elephants from a population centered around Amboseli have been shot and killed, most likely by trophy hunters, in the Tanzanian part of this wildlife corridor. At least two were so-called super tuskers, with tusks so long that they swept the ground.

There hasn’t been a similar cluster of rapid killings in the area since the mid-1990s. Conservationists say it points to a breakdown of a tacit agreement between the countries that banned hunting in the border zone.

“This is heartbreaking for me,” said Cynthia Moss, an American zoologist monitoring the roughly 2,000 elephants in the Amboseli herd as director of the Amboseli Trust for Elephants. About 10 of Amboseli’s super tuskers are left, and an additional 15 or so remain across the Kenya, she said. “I know these elephants. I know how trusting they are.”

The killings have sparked an uproar in Kenya. In April, scores of leading conservationists wrote an open letter to the Tanzanian government demanding that the authorities ban hunting within 25 miles of the Kenyan border.

A spokesperson for the Tanzanian Ministry of Natural Resources and Tourism, asked for comment, said the country’s conservation strategy was based on “a strong foundation of regulation, research and scientific evidence” and noted that Tanzania had one of the most abundant elephant populations in Africa. Government statements in the past have justified hunting on the grounds that it brings in millions in much-needed income.

Kenya’s wildlife service did not respond to repeated requests for comment.

Kaddu Sebunya, who heads the African Wildlife Foundation, a conservation organization based in Kenya, said it was unlikely that the elephants had been shot by poachers. He noted that there were no signs of an investigation by the Tanzanian authorities. “If a poacher were to kill an elephant illegally at the same site, they would be dealt with by law,” he said.

Elephant killings on the Tanzanian side three decades ago prompted similar anger and led to the announcement of a moratorium on hunting.

In December 1994, three Amboseli elephants were killed in quick succession near Longido, a town about nine miles from the border, prompting an outcry from Kenya. By May 1995, the Tanzanian authorities, under pressure from conservationists and scientists in Kenya and around the world, announced a nine-month ban on hunting in the area.

The moratorium, Tanzanian officials said, would be lifted once the two countries agreed to a clear, defined conservation area in talks.

That’s where things get muddy. While old newspaper clippings confirm that the ban was announced, it’s unclear whether talks were ever held or whether the nine-month restriction was ever lifted. No evidence appears to exist of any further action. But, for whatever reason, hunters had avoided the area until recently.

Ms. Moss and other conservationists in Kenya say there was an unspoken agreement between the two countries after the initial announcement, and it appears to have fallen apart. Experts say they don’t know why. Tanzanian conservation law has not changed.

Hunters, meanwhile, say the lack of clarity means the agreement simply did not exist.

Tanzania has about 60,000 elephants today, down from some 316,000 in 1978. In Kenya, about 35,000 remain, down from approximately 160,000 around the same time.

As a keystone species, elephants not only shape ecosystems for other wildlife — by creating watering holes with their tusks, for example, and dispersing seeds in their droppings — but their intelligence and sophisticated social structure mean violent deaths could traumatize surviving elephants and result in aggressive behavior.

The bigger, older bulls being targeted are considered crucial for reproduction, and also for transmitting culture and maintaining social order. Male elephants live mostly outside herds, and young bulls will sometimes spend time with older ones who pass on knowledge, like where to forage and where to go when the seasons change.

They also model behavior. One study found that an absence of older males can make younger bulls more aggressive.

According to Mr. Sebunya, super tuskers even help younger bulls understand which humans to avoid. “They tell them, ‘When you see these tourist vehicles, those are OK, But if you see other types of vehicles, those are problems,’” he said.

The first elephant lost in the recent wave, Gilgil, a 35-year-old who was killed in September, was one such big tusker.

Singling out elephants like Gilgil, Ms. Moss said, “takes away the natural elements of competition and survivorship, allowing younger, less tested, perhaps less vigorous, males to reproduce.”

Sporting groups, on the other hand, assert that hunting, when properly managed, can be a net positive in a poorer country like Tanzania. (G.D.P. per capital in the country is about $1,200, according to the World Bank, compared with roughly $2,100 in Kenya.)

Zidane Janbeck and Quintin Whitehead, who run Kilombero North Safaris — which offers hunting trips for elephants, lions, leopards and other big game — say the company shares a percentage of its revenue with communities that own some of the hunting territory. (Kilombero said it paid the Enduimet Wildlife Management Area a total of $250,000 in 2023. Enduimet officials did not respond to a request for comment.)

In addition, human-elephant clashes are rising in Tanzania, in part because of the country’s rapidly growing rural population and also because of more frequent and more intense droughts in East Africa. But farmers are less likely to kill elephants that invade their fields, hunters say, if they know they’ll receive a share of hunting revenue.

And setting aside well-managed wilderness areas for hunting means less land will be razed for agriculture, they add.

Tanzania sets yearly quotas for animals to be hunted (50 elephants this year) and each hunting party must be monitored by an official.

Kilombero confirmed that it had hunted an elephant in the area where Gilgil’s carcass was found, his tusks removed, but denied it had killed a super tusker.

“We are guaranteeing you, we are conservationists, we’re not targeting big elephants,” Mr. Janbeck, who led the September hunt, said in a video interview. “We’re doing everything under the regulations in Tanzania. We’re backed up by the government. We have all the blessings from the local communities.”

In Longido, locals seem split.

On a recent weekday, a group of men gathered for late-evening drinks and weighed their stance on trophy hunting. As long as it’s legal, fine, one older man concluded. A soft-spoken younger man countered, saying killing for sport was not right.

But do the men benefit from hunting revenue? “No,” they all said in unison, shaking their heads. The authorities favor wild animals and sport hunters but abandon vulnerable farmers, they said.

“You have to take a loan to grow your farm and these elephants destroy it and we get nothing,” a farmer, Edward Masaki, 53, said in Swahili with a heavy frown.

“Right now I have men guarding my farms day and night with flashlights,” he said. “The annoying thing is, you can’t kill the animals when they attack.”

He was referring to a nationwide ban on wildlife killing that Tanzania has put in place to guard against poaching. Killing animals without a permit carries a stiff prison term: from three years to 30 years.

Meanwhile, conservationists across the border in Amboseli say they are waiting in dread, fearing news that another big tusker has been killed, even as they scramble to get a response from the Tanzanian government.

“All our pleas have landed on deaf ears,” Ms. Moss said. If the killings continue at the same pace, she said, Amboseli’s tuskers will be wiped out in two years, transforming the ecosystem in unprecedented and negative ways.

“A population that is hunted becomes unnatural because humans are choosing who should pass on his genes and who should not, who should live and who should die,” she said.