Florida documented for the first time the death of an American crocodile associated with lead poisoning, after researchers found more than 22 grams of the metal in the stomach of a specimen that died shortly after being captured in Miami-Dade.
The Florida Fish and Wildlife Conservation Commission (FWC) documented the case through its research institute and specified that this is the first apparent case of mortality associated with lead poisoning in an American crocodile in Florida.
The agency, however, makes an important clarification: the researchers did not conclude that lead was necessarily the sole cause of death, but rather that the poisoning weakened the animal and contributed to its inability to withstand the stress of capture and the subsequent procedure.
The case dates back to November 17, 2023, when a Florida Fish and Wildlife Conservation Commission crocodile response agent was called to a residence after receiving a report about an individual that had entered an outdoor pool.
It was a female approximately seven feet long. The animal was captured, and the researchers took the opportunity to attach a GPS transmitter as part of the FWC's urban crocodile research project.
Initially, the crocodile was active and alert, but during the procedure, it began to show concerning signs. Shortly after being released into a nearby canal, it unexpectedly died.
The biologists then performed a field necropsy and found 22.42 grams of lead in its stomach. Among the recovered objects were 23 air rifle pellets, a weight used for fishing, and other small fragments of lead.
They also found remains of at least one green iguana, an invasive species widely spread in Florida.
The joint presence of the pellets and the reptile remains led researchers to consider that the crocodile may have ingested some of the lead while feeding on an iguana that had previously been shot with ammunition made of that metal.
The FWC also noted that the animal had lost most of its teeth, a clinical sign consistent with prolonged exposure to lead. Subsequent analyses also detected elevated concentrations of the metal in its tissues.
The scientific study on the case, published in 2026 under the title An apparent case of Pb toxicosis in an American crocodile Crocodylus acutus in South Florida, USA, found a concentration of 78.06 parts per million of lead in the liver and 0.35 parts per million in samples from its scales.
The authors concluded that chronic exposure to lead likely reduced the overall health of the animal and its ability to withstand the stress associated with capture, thus intoxication would have contributed to its death.
The discovery represents, according to researchers, the first apparent case of mortality associated with lead poisoning in this threatened species in Florida, although they warned that other crocodiles may be affected without the full extent of the problem being known.
The case also raises questions about a possible contamination pathway related to the control of green iguanas. These animals are considered invasive in Florida and can be humanely euthanized under certain circumstances, including the use of air rifles that may employ lead pellets.
If a slain iguana remains in the environment and is subsequently eaten by a predator or scavenger, the pellets can end up being incorporated into the food chain.
The fishing weight found in the crocodile's stomach suggests that there are other sources of exposure to the metal beyond just ammunition.
After the discovery, the Fish and Wildlife Research Institute (FWRI) in Florida launched a monitoring program for pollutants in American crocodiles.
Researchers are collecting tissue samples whenever they have the opportunity to determine the extent to which lead and other contaminants are affecting the crocodile population in the state.
The FWC acknowledges that the extent of the problem is still unknown and considers it necessary to expand the samples before determining whether this is an exceptional event or a more widespread threat to the species.
American crocodiles (Crocodylus acutus) are federally protected, and in the United States, their distribution is mainly concentrated in southern Florida, where they inhabit coastal areas, estuaries, and brackish water channels.
The presence of alligators in residential areas of South Florida has led to other recent incidents. In 2024, 21 baby alligators were rescued from a pool filter in Miami-Dade before being measured, tagged, and returned alongside their mother.
Months earlier, a seven-foot crocodile had raised concerns among residents of another area in Miami-Dade, although the FWC then determined that the specimen did not meet the criteria for removal.
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