The decomposed remains of P-55, the first known mountain lion to successfully navigate across the 101 Freeway twice, were recently discovered by a biologist, officials with National Park Service announced Wednesday.
It was not immediately clear when the approximately 3-year-old cougar died because his collar failed to "emit a mortality signal," according to a post on the Santa Monica Mountains National Recreation Area's Facebook page.
The remains were also "already too decomposed" to determine a cause of death, the post stated.
However, officials think he possibly died from ingesting rat poison or after a fight with another male mountain lion, though they noted there were no signs of a struggle.
"He was a beautiful animal who survived longer than most males in the Santa Monica Mountains, but ultimately met his end at a relatively young age," Ranger Kate Kuykendall wrote in the Facebook post.
The puma was seemingly healthy before the abrupt discovery, officials said.
He was known to roam the northwestern end of the Santa Monica Mountains, usually west of Las Virgenes Road and north of Mulholland Drive.
P-55 made headlines last October when he became the first known puma to cross the 101 twice, doing so in Thousand Oaks west of State Route 23.
It was the fourth and fifth such successful journeys across the 101 since 2002, when the park service began its study of big cats in the area.
P-55 first crossed into the Santa Monica Mountains into the Santa Susanas about a year ago; he then made the dangerous trek back across the freeway a little more than two months later.
He also crossed state routes 23 and 118 in July 2017.
Additionally, the young male puma was tracked near homes multiple times, including an instance late last July when he was captured on camera strolling through a Newbury Park backyard.
He was also spotted in Westlake Village earlier this year, pressed up against a sliding glass door in what the residents described as a possible attempt to get inside the house.
P-55 was first captured and identified in April 2017 along with another male big cat, P-56, rangers said at the time. The two were thought to possibly be brothers.