Adult female mountain lion P-54 and her full-term fetuses were exposed to multiple anticoagulant rodenticides


A mountain lion that was struck and killed by a vehicle earlier this year, was found to be pregnant with four kittens. According to biologists from the National Park Service (NPS), all five animals tested positive for multiple anticoagulant rodenticides (rat poison).

“This is the first time during our 20-year study that we’ve been able to test mountain lion fetuses for anticoagulant rodenticides,” NPS biologist Jeff Sikich said in a statement.

Traumatic injuries, including multiple fractures to the ribs and left femur, were the cause of death

Biologists say that the results from P-54 and her kittens show that exposure to toxicants is still widespread and repeated, given the presence of five different compounds, in wildlife in and around the park.  

The event also highlights two of the significant sources of mortality for wildlife in the area— vehicles, and toxicants. 

“A primary goal of our work is to learn whatever we can about these animals and how their lives are affected by the urban landscape they inhabit. Unfortunately, we’ve learned that mountain lions are susceptible to rat poisons even before they are born,” Sikich said. “In this case, it is also unfortunate because the death of P-54 from a vehicle resulted in the loss of four other young mountain lions, two males and two females, that were about to enter the population.”

The 5-year-old cat was killed on Las Virgenes Road between Piuma Road and Mulholland Highway at around 9:30 a.m. on June 17, 2022. Her body was taken to the California Animal Health and Food Safety (CAHFS) Lab in San Bernardino for a necropsy and testing. She was also at least the third local mountain lion to die while crossing Las Virgenes/ Malibu Canyon Road in recent years.

The location where P-54 was hit was near where her mother was struck and killed in 2018 – just a little further north on the same road, according to the NPS. P-54 was one year old at the time of her mothers death, which is during the early end of when kittens typically leave their mother.

Other results showed that like almost every other mountain lion tested in and around the Santa Monica Mountains, anticoagulant rodenticide (AR) compounds were detected in her liver. She had been exposed to five compounds (brodifacoum, bromadiolone, chlorophacinone, difethialone, and diphacinone). The neurotoxic rodenticide bromethalin was also detected in her abdominal fat tissue.  

All four full-term fetuses were exposed to three anticoagulant compounds (bromadiolone, chlorophacinone, and diphacinone), and three of the four were also exposed to brodifacoum. These included first-generation AR compounds, diphacinone and chlorophacinone, and longer-lasting and faster-acting second-generation compounds, bromadiolone and brodifacoum. NPS researchers have now documented the presence of anticoagulant rodenticide compounds in 39 out of 40 local mountain lions tested, including these four fetuses.