NPS Biologists Report Abnormalities Linked to Mountain Lion Inbreeding in P-81
By JENNIKA INGRAM | Reporter
Mountain lions in the Santa Monica Mountains have had a challenging year with unexpected deaths and a dwindling population—but this summer brought the first big litter of new kittens.
“In total, 13 kittens were born to five mountain lion mothers between May and August 2020,” according to a statement from National Parks Service. “It’s the first time this many mountain lion dens have been found within a short period of time during the 18-year study, in which a total of 21 litters of kittens have been marked at the den site by researchers.”
By comparison, the highest number of kittens born prior to this was four in a 10-month period in 2015.
“This level of reproduction is a great thing to see, especially since half of our mountains burned almost two years ago during the Woolsey fire,” Jeff Sikich, a wildlife biologist who has been studying the mountain lion population in the Santa Monica Mountains, shared in a statement. “It will be interesting to see how these kittens use the landscape in the coming years and navigate the many challenges, both natural and human-caused, they will face as they grow older and disperse.”
The birth of so many kittens comes on the heels of scientists discovering the first mountain lion with inbreeding deformities in the region. A young mountain lion captured and collared in the Santa Monica Mountains on March 4, known as P-81, appears to have reproductive and tail defects.
The mountain lion, approximately 1 and a half years old, has a kinked tail where the end is shaped like a letter “L” and only one descended testicle, according to biologists with the National Parks Service.
Similar physical abnormalities were linked with inbreeding depression in mountain lions in Florida.
“In a 2016 paper co-authored with biologists at UCLA, modeling predicted a 99.7% chance of extinction within 50 years, with a median time to extinction of just 15 years, if similar inbreeding depression occurred in the Santa Monica Mountains population,” the statement explained.
“This is something we hoped to never see,” Sikich said of the critical discovery. “We knew that genetic diversity was low here, but this is the first time we have actually seen physical evidence of it. This grave discovery underscores the need for measures to better support this population.”
A couple of days later, another mountain lion, also with a kinked tail, was recorded on a remote camera in the same area, potentially a sibling, and then a third mountain lion with similar traits.
“Along with a similarly isolated population in the Santa Ana Mountains south of LA, we have seen the lowest levels of genetic diversity ever documented in the west,” Seth Riley, wildlife branch chief in the area, said.
A loss of genetic diversity, called “genetic drift,” can happen when there is a small population of animals or through inbreeding, and both are occurring in the Santa Monica Mountains, Riley said.
“The only population with lower levels was in south Florida a couple of decades ago, when Florida panthers were on their way to extinction,” the statement continued. “The really interesting, and worrying, thing is that they saw the same type of kinked tails and cryptorchidism there. Cryptorchidism is when one or both testes fail to descend. In Florida, males with neither teste descended were not able to reproduce and were likely sterile.”
By importing eight female mountain lions from the closest state, Florida was able to breed the remaining males and bring in new genetic material, and it was successful reducing these defects.
Riley explained that in the west, since there are other large populations of mountain lions, it “makes more sense to increase connectivity,” and this new information proves the urgency.
A proposed $87 million wildlife overpass to connect populations of mountain lions south of the 101 Freeway to those other natural areas in the Simi Hills, Santa Susana Mountains and Los Padres National Forest would allow all sorts of animals to move around traffic and would be the first in a large metropolitan area, according to the statement.
“If fundraising stays on track, construction is slated to begin in late 2021, officials say,” according to the statement.
The National Wildlife Federation is helping raise the funds through a national campaign, with the proposed wildlife corridor slated to open in 2023.
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