Mountain lions once used to occupy the entire United States coast-to-coast, but today they are mostly found in 14 western states. The Mountain Lion Foundation charity estimates the national population is unlikely to be more than 30,000.

One June 17, a five-year-old mountain lion known as P-54 was killed on Las Virgenes Road in the Santa Monica mountains. She was born in January 2017, and National Park Service (NPS) researchers fitted her with a tracking device the following month.

Post-mortem inspection showed that the mountain lion died from traumatic injuries as a result of the collision. She was pregnant with four kittens at full term when she was killed. “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,” biologist Jeff Sikich, from the mountain lion project at Santa Monica Mountains National Recreation Area, said in a statement.

P-54’s mother, P-23, was also struck and killed by a vehicle along the same road in 2018.

Testing also showed that the mountain lion had five anticoagulant rat poison chemicals in her liver, while a further neurotoxic rat poison was found in her abdominal fat tissue.

Similar findings are common in almost every other mountain lion tested in and around the Santa Monica mountains, but P-54’s case presented a unique opportunity for NPS researchers to test mountain lion fetuses for the rat poison chemicals as well.

They found that all four fetuses had been exposed to at least three of the rat poison compounds: bromadiolone, chlorophacinone, and diphacinone. Of those four fetuses, three were also exposed to a fourth: brodifacoum.

“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,” Sikich said.

“Unfortunately, we’ve learned that mountain lions are susceptible to rat poisons even before they are born.”

Anticoagulant rodenticide, or anticoagulant rat poison, are poisons used to kill mice, rats, and other rodents by preventing blood clotting. They do this by interfering with a process that recycles vitamin K1, which helps control bleeding by enabling blood clots.

Ingestion can result in spontaneous bleeding either internally or externally that leads to death.

While rat poisons may be targeted at rodents, they are also toxic to many mammals and birds including farm animals, pets, and wildlife—as well as humans.

Symptoms of poisoning may include blood in urine and stools, bruising and bleeding under the skin, altered mental status, low blood pressure, nosebleed, pale skin, shock, and vomiting blood, according to MedlinePlus.

NPS biologists say the presence of rat poison in P-54 and her fetuses shows that exposure to toxicants is widespread and repeated in and around the Santa Monica Mountains area.