Captive cheetahs are more vulnerable to lead poisoning than big cats in the wild
Captive cheetahs have substantially higher amounts of lead in their systems compared to wild cheetahs or leopards.
“We found about 4-5 times more lead in captive than in wild cheetahs,” said Catherine Hauw, a wildlife veterinarian and doctoral student at Wits University in South Africa. “There is way more lead in the bones of captive cheetahs.”
Scientists have long documented the negative effects of lead ammunition poisoning on wildlife. Lead bullets shatter on impact, contaminating about 40 cm around the entry wound with micro-fragments of lead. Many big game hunters, like gazelles, field dress their kills and leave behind contaminated organs or carcasses that scavengers prey on. Smaller scavengers, like birds, can get sick and even die from acute lead poisoning. This is especially a challenge in Namibia and South Africa, where nonlead ammunition is not widely available.
Although cheetahs (Acinonyx jubatus) in the wild rarely scavenge, those in rehabilitation centers face another challenge: workers often feed them game meat killed with lead ammunition. Although cheetah mortality from lead poisoning is rare, one cheetah recently died from consuming a lead bullet in the final stage of rehabilitation before being released back into the wild.
To better understand how lead poisoning is affecting wild and captive cheetahs over time, Hauw collaborated with the Cheetah Conservation Fund (CCF), a cheetah rescue, research and education nonprofit in Namibia. Hauw analyzed the bone lead concentrations of dozens of captive and wild cheetah skeletons as well as wild leopards (Panthera pardus) provided by CCF. She dissolved a small piece of the tibia bones in acid to determine the amounts of lead in the bones. “In bones, you can measure lifelong cumulative exposure of lead,” Hauw said.
Her findings, which she presented at the 2024 TWS Conference in Baltimore, Maryland, showed that wild cheetahs—which are listed as vulnerable on the IUCN Red List and considered endangered by the Namibian government—had the lowest lead levels (0.38 mg/kg), followed by wild leopards and finally captive cheetahs (1.44 mg/kg).
Hauw thinks that the two wild species’ hunting strategies resulted in different chronic exposure to lead. While leopards are opportunistic scavengers—they will take advantage of a carcass left behind by a hunter—wild cheetahs usually only eat their own fresh kills. “We showed that by using lead ammunition, you’re hurting your scavenging wildlife,” Hauw said.
However, CCF staff fed the cheetahs in captivity horse or donkey meat shot by lead ammunition because they don’t have access to other ammunition. While the animals are usually shot in the head to spare the meat, Hauw said that this doesn’t fully protect the animals from lead poisoning. “For enrichment purposes, staff give the heads to cheetahs about two times a month,” she said. Throughout time, these exposures can add up. Even if they don’t cause mortality, it can be problematic.
“The difficulty is that you don’t see any poisoning when it’s at chronic levels,” she said. “Those cheetahs are doing well—there are no clinical signs.” Similarly to in humans, though, small amounts of lead poisoning over time can have negative effects that are harder to notice. “Little by little, it’ll affect your liver, your kidneys and cognitive function,” she said.
Accessing alternatives
With only 6,700 cheetahs in the wild, Hauw said that trying to rehabilitate animals with lower cognitive functioning who can’t hunt properly or have lower reproductive functions can add another hurdle to an already challenging endeavor.
“You are silently poisoning them,” she said. “Lead has been called a silent killer because you can’t see it, but it hugely affects your internal organs,” she said. In wildlife, there are no clinical signs until it’s too late.
The last step before reintroduction, though, can be the most risky for cheetahs, which is where the recent acute lead poisoning and death occurred. They are released into bomas, which are fenced-in enclosures without predators. There, they receive entire carcasses to practice eating before they’re released back into the wild, where they’ll have to fend for themselves. This is how the cheetah at CCF ingested an entire lead bullet and died of acute lead poisoning. “The bomas have been said to be an actual danger to these animals,” she said.
Solving the problem of lead poisoning in wildlife in part comes down to access to alternatives, Hauw said. At CCF in Namibia, they tried to import enough nonlead ammunition for CCF’s needs, and it took 14 months.
Hauw said if you can’t find nonlead ammunition for use in bomas, removing both the bullet and 40 cm of flesh—about 16 inches—around the wound could help lower the risk of lead poisoning. She said that outreach and communication are the most important, including sharing the message that lead ammunition affects not only scavengers but humans, too. “Pushing toward awareness is the key,” she said. “Awareness is more important than laws at the moment.”
