Mysterious jaguar deaths now under investigation in Brazil

Thanks to tracking collars, federal police are investigating the possible poisoning deaths of two jaguars in the Pantanal.

By Jill Langlois
Published 15 Oct 2021, 13:16 BST
A male jaguar emerges from the water hyacinth at the edge of a tributary of the Cuiaba River, in Brazil. As ranchers graze their livestock in former jaguar territory, attacks on cattle are not uncommon. In retaliation, some ranchers leave out pesticides to poison the big cats.
Photograph by Nick Garbutt / Barcroft Media, Getty Images

Sandro was dead almost a month before his body was recovered.

A GPS tracking collar led researchers to his remains in an area of the Brazilian Pantanal known as Otter’s Pass. They had been monitoring the adult male jaguar for nearly a year when the collar alerted them that he had stopped moving in May.

Trips into the world’s largest tropical wetland require careful planning and funding, so it was June before the researchers finally were able to get into the field to find out what happened. What they found shocked them.

As they tracked the collar across one of a thousand cattle ranches in the region, scouring the area where it last registered Sandro’s movements, they found another jaguar—not one they had been monitoring—lying dead in the grass.

Just 164 feet away was Sandro, his collar still intact.

There were no marks on their bodies—no signs they had been in a fight, no gunshot wounds.

“These were two jaguars, two healthy animals, dead so close to one another,” says Antonio Carlos Csermak, Jr., a veterinarian and researcher with Reproduction 4 Conservation (Reprocon), the group tracking the jaguars. “That’s when we started to suspect they had been poisoned.”

When the researchers returned three days later, with federal police and agents from the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA), which enforces federal environmental laws and treaties, they pinpointed the last GPS point where Sandro had spent significant time, likely eating. About 320 feet from the first jaguar was a cow carcass. Scattered around it were another 17 dead animals: 14 vultures, two carcara raptors, and a crab-eating fox.

Csermak and his colleagues had long heard that ranchers, frustrated with jaguars killing their cattle, would use pesticides to try to put an end to the problem. When ranchers found one of their animals dead, they would cover it in poison, figuring the jaguar would return to continue eating. (See why pesticide poisoning is also a growing threat to wildlife in Africa.)

The suspected pesticides of choice have an active ingredient called carbofuran, a neurotoxin so poisonous that it’s banned or severely restricted in Brazil, Canada, the European Union, Australia, and China, and is prohibited for use on food crops in the U.S. Reprocon team and Brazil authorities suspect the poison is being smuggled over the porous borders the Brazilian Pantanal shares with Paraguay and Bolivia. But they never had proof—until now.

Because of Sandro’s tracking collar, they were able to find his body and collect tissue samples—potential evidence of a crime. For the first time, federal police and IBAMA are investigating the poisoning deaths of two jaguars in the Pantanal.

Brazil is thought to be home to about half of the 170,000 jaguars still left in the wild. With a population of roughly 2,000, the Pantanal has one of the highest densities of jaguars in the world.

The Pantanal is the largest wetland on the planet, extending across Brazil, Bolivia, and Paraguay. It’s home to more than 4,000 species of plants and animals, including the world’s densest population of jaguars, but scientists and activists warn the ecosystem is at risk of collapsing.
Photograph by CARL DE SOUZA/AFP, Getty Images

Jaguars are listed on the IUCN’s Red List of Threatened Species as near threatened, with a decreasing population. Increasing deforestation to clear space for human activities like cattle ranching has left jaguars with lost or fragmented habitats and isolated populations, making it difficult for them to breed. A smaller range means the cats have less access to prey, leaving them no choice but to turn to livestock to survive. And when they do, ranchers often look for any means available to retaliate.

Renato Raizer was with Reprocon when the group first put the tracking collar on Sandro. He was also with them when they found the jaguar’s body. A rancher who has been running the family cattle farm alongside his father for the last 12 years, he says he would never kill a jaguar, even though he loses roughly 50 animals to them every year. (Claw marks on a cow’s neck and bite marks straight through the skull are tell-tale signs of a jaguar attack.)

“There isn’t much we can do,” he says. “If you have a small farm, maybe you could build an enclosure, keep your cattle in for the night. But what do you do if you have a thousand, 2,000, 15,000, 80,000 heads of cattle? You just take the loss. It might be my property, but it’s their home too.”

Not everyone thinks that way. Before it was filled with cattle, the native pastureland where Sandro and the other animals were found was a tourist hot spot. People from around the world flocked there, hoping to catch a glimpse of a jaguar in the wild. And they usually did. Its location on the edge of the Miranda River meant it attracted more jaguars than most properties in the region.

Gian Peralta, a wildlife tour guide, rented the ranch from 2012 to 2019, before it was purchased by its current owner. When he was there, business was good, he says. Every day he’d see two or three jaguars. Sometimes he’d draw them out using an instrument that mimics the sounds of jaguars looking for a mate. Other times he wouldn’t need it. They’d be easily spotted, resting on the riverbank.

He first noticed something was off last year.

“When I was going along the dirt road where the jaguars always cross, I wasn’t seeing their paw prints anymore,” Peralta says.

Now, as he continues to work nearby, still using the Miranda River as a means for transportation, Peralta says he’s lucky if he sees one jaguar a day. He often goes several without seeing any.

Yards away from an injured jaguar, cattle in the Porto Jofre region of the Pantanal drink water. As grazing land for cattle expands into jaguar habitat, predator and prey are in increasingly close quarters.
Photograph by Photo by MAURO PIMENTEL/AFP, Getty Images

When he left the property in 2019, he warned the old owner not to sell or rent it to someone who would use it for cattle, but the man didn’t heed his advice. Peralta says that as soon as he heard about the dead jaguars, he was sure they’d been killed there.

Once the story hit the news, rumours started. Some residents and ranchers say they saw another nine dead jaguars on the property where Sandro was found. Others say there were seven.

But by the time federal police carried out a search warrant at the ranch, it was August 5, almost two months after the jaguars were found. Because the case was well publicised, says Claudinei Santin, the agent heading the investigation, the police are sure the landowners and employees knew they were coming.

There was no evidence of other dead animals on the property and nothing to prove the presence of carbofuran-laced pesticides. Law enforcement seized cell phones from the ranch’s administrator and renter, who Santin says is their main suspect.

A search warrant for the suspect’s home in Campo Grande also turned up nothing. Police couldn’t search the quarters of the suspect’s two employees because they’d already moved on to work on another farm in a more remote area of the Pantanal that police are struggling to reach.

A jaguar lays on the banks of the Cuiaba River in Pantanal. In addition to retaliatory killings by livestock owners, jaguars face threats from habitat loss and fragmentation as well as poaching for the illegal wildlife trade.
Photograph by Photo by Buda Mendes/Getty Images

An analysis of tissue samples from the jaguars is ongoing, although federal police say tests are unlikely to detect carbofuran because of the level of decomposition of the animals when they were found. They are, however, sure the animals were poisoned.

“Because of the dead insects found on the bovine carcass and the distribution of the dead animals at the location—the smaller the animal, the closer it died to the bovine carcass—the federal police forensics team concluded that the animals died by poisoning from the carcass,” says a statement from the federal police.

And while this is the first time they’re officially investigating a jaguar poisoning, Santin says they have now been “alerted to similar occurrences at other ranches in the southern Pantanal of this state [Mato Grosso do Sul].”

Killing an endangered animal and importing and using a banned toxic substance carry a combined sentence of up to five years in prison.

“The biggest difficulties we have [investigating these types of cases] are related to distance, breadth, isolation, and difficult access to ranches in the region,” he says. “And you can see in this case, the only way we were able to discover the poisoning and death of these animals was because of one jaguar who was being monitored with a GPS tracking collar.”

For others, such as Raizer, the benefits of the collars go beyond investigating crimes. They could also act as a deterrent, making it so that ranchers—leery of possible legal repercussions—don’t poison them at all.

Wildlife Watch is an investigative reporting project between National Geographic Society and National Geographic Partners focusing on wildlife crime and exploitation. Read more Wildlife Watch stories here, and learn more about National Geographic Society’s nonprofit mission at Send tips, feedback, and story ideas to


Explore Nat Geo

  • Animals
  • Environment
  • History & Culture
  • Science
  • Travel
  • Photography
  • Space
  • Adventure
  • Video

About us


  • Magazines
  • Disney+

Follow us

Copyright © 1996-2015 National Geographic Society. Copyright © 2015-2023 National Geographic Partners, LLC. All rights reserved