Lion and leopard populations in Zambia's Kafue National Park are showing signs of a comeback, following many years of poaching. A new early-warning system involving birds has been a part of the success.

A new report shared with the Reuters news agency found that big cat numbers across Kafue remained similar -- and in some cases increased -- from 2018 to 2022. The populations were measured widely for the first time by Panthera. The organization works to save wild cats.

A lack of historical population data makes it difficult to examine population changes over a longer period of time. But since 2018, scientists have seen signs that the big cat populations are increasing, said Kim Young-Overton. She is director of Panthera's Kavango-Zambezi Transfrontier Conservation Area program, which includes Kafue.

A half-century of poaching has greatly hurt wildlife populations in Africa's third-largest national park. Kafue's big cats are among the victims.

Leopards have long been hunted for their skin, which people use to make ceremonial clothing. Poachers have also targeted the grass-eating animals that lions eat, leaving too little food behind for the hungry cats. Area farmers have targeted the lions with weapons like guns, arrows, and even poison.

Conservation groups have worked alongside Africa Parks and Zambia's Department of National Parks and Wildlife to help protect Kafue's wildlife. The groups and organizations use many different tools in their efforts.

One of the newer methods is tagging, or marking, vultures with satellite trackers. The birds are drawn to dead animal carcasses, or bodies. And so are big cats. The quick arrival of the vultures lets wildlife managers know about possibly poisoned carcasses – before the lions and leopards can get to them.

In many parts of Africa, livestock owners will poison cow carcasses with a deadly agricultural chemical meant to kill the cats that eat them. The farmers see the poisoning as a form of punishment for lions that kill and eat their animals.

Scientists have tagged two kinds of vultures, including the endangered white-backed vulture. Their population has dropped by more than 90 percent across West Africa in the past 40 years, largely due to poisoning.

Corinne Kendall leads conservation and research efforts at North Carolina Zoo in the United States. The zoo leads the vulture-tagging program in Zambia. She said, "African white-backed vultures will come in really large numbers." A hundred or more of the birds may try to eat a poisoned carcass. All of them will die, Kendall added.

Since 2021, the zoo team has tagged 19 vultures in Zambia. The birds wear very small bags containing the satellite tags over their wings.

So far, the tagged vultures have led the wildlife teams to two suspected poisoning events near Kafue. In such cases, park workers were able to remove the carcass and try to find the people responsible for the poisoning. This helps save both the birds and the big cats.

"Poisoning is a silent killer," Kendall added. "Unless you have something like satellite-tagged vultures, a lot might be going on without anyone knowing about it."

I'm Gregory Stachel.

Gloria Dickie reported this story for Reuters. Gregory Stachel adapted it for VOA Learning English.

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poach – v. to catch or kill an animal illegally

conservation – n. the protection of animals, plants, and natural resources

tag – n. a small piece of cloth, paper, metal, etc., that is attached to something and that has information written on it

track – v. to follow and try to find (an animal) by looking for its tracks and other signs that show where it has gone

manager – n. someone who is in charge of a business or department

livestock – n. farm animals (such as cows, horses, and pigs) that are kept, raised, and used by people

zoo – n. a place where many kinds of animals are kept so that people can see them

silent – adj. giving no information about something