Scientists who have been studying Santa Monica Mountains’ dozens of cougars for the past 18 years have made a “grave discovery” linked to the animals’ chances of survival, officials announced Wednesday.

In March, researchers in the western part of the range found a 1 1/2-year-old male mountain lion with its tail shaped like the letter L. The cougar, called P-81, also only has one descended testicle.

“This is something we hoped to never see,” wildlife biologist Jeff Sikich said in a statement from the National Park Service. “We knew that genetic diversity was low here, but this is the first time we have actually seen physical evidence of it.”

Experts have previously connected such physical abnormalities with inbreeding depression in Florida’s mountain lions, NPS said.

Inbreeding depression occurs when there is a lack of genetic diversity due to the animals mating with close relatives. This doesn’t bode well for reproduction or the survival of the population, NPS said.

Among Florida’s male mountain lions, cryptorchidism, a condition in which one or both testes don’t descend, means they’re likely sterile, according to the Park Service. The rate of kittens survival rate was also low, with some of them developing holes in their hearts.

In April, California wildlife regulators granted Southern California’s mountain lions a temporary endangered species status. The state’s cougars are not currently classified as endangered or threatened, but advocates argued that human development has prevented the animals’ movement, therefore causing genetic isolation and low survival rates.

NPS cited a 2016 paper co-authored by UCLA biologists, which predicted a 99.7% chance of extinction of Santa Monica Mountains’ cougars within 50 years if they experience inbreeding depression like that seen in Florida. The median time to extinction was 15 years, the scientists’ modeling showed.

A couple of days after Santa Monica Mountains’ biologists discovered P-81, footage from the same remote area showed another male mountain lion with a kinked tail. It’s possible the two are related, perhaps siblings, according to NPS.

More recently, video showed a third mountain lion with a deformed tail in the eastern Santa Monica Mountains between the 405 and Hollywood freeways, officials said.

Florida scientists who feared the extinction of local mountain lions imported eight female cougars from Texas.

“The experiment, a genetic rescue of sorts, succeeded,” NPS said. “There are now estimated to be about 200 mountain lions in the population from a low of 20-30. Genetic diversity also greatly increased, and the incidence of various defects plummeted.”

The wildlife branch chief for the Santa Monica Mountains National Recreation Area, Seth Riley, said local officials could potentially bring mountain lions from elsewhere in the state.

But he argued that evidence of inbreeding depression–instead of just low genetic diversity, which happens over time when there’s a small population of a species–just underscores the urgency of building a wildlife crossing to connect mountain lions south of the 101 Freeway to those in Simi Hills, the Santa Susana Mountains, and the Los Padres National Forest.

“The wildlife overpass would allow mountain lions and other animals to move over more lanes, and more traffic, than any previous such projects around the world, and it would be the first in a large metropolitan area,” NPS said. “It will be constructed in the Liberty Canyon area of Agoura Hills, one of the last places left along the 101 Freeway where natural, protected, habitat abuts the road on both sides.”

The proposed crossing is currently in the final design phase, and if funds are raised as expected, construction could begin in 2021, authorities said.

The National Wildlife Federation is raising money through a national campaign, according to NPS.

In addition to the federal agency and the nonprofit, the Resource Conservation District of Santa Monica Mountains, the California Department of Transportation and the Mountains Recreation and Conservation Authority are working on the project.

“The truth is that we want to build that connectivity not just for the mountain lions, but for all of the wildlife,” Riley said.