Signs of inbreeding among SoCal lions raise fears of extinction

LOS ANGELES (CNS) – Scientists tracking two local mountain lion populations, one in the Santa Monica Mountains and another in the Santa Anas, have identified the first signs of inbreeding among these groups, cut off from breeding opportunities by busy highways.

According to the UCLA-led study – available online and published in the January 2022 issue of the journal Theriogenology – the animals had an average sperm rate of 93%, while some also showed physical signs of inbreeding, such as deformed tails or testicular defects.

What you need to know

  • Scientists tracking two local mountain lion populations have identified the first reproductive signs of inbreeding among these groups
  • According to the study conducted by UCLA, the animals had an average sperm rate of 93%, while some also showed physical signs of inbreeding, such as deformed tails or testicular defects
  • The researchers said the results make the need for wildlife crossings more urgent, structures that allow the mountain lions and other animals to migrate further and find a larger pool of potential mates
  • The California Department of Transportation has planned the groundbreaking ceremony for a wildlife crossing on the 101 Freeway in Agoura Hills in early 2022

Researchers have long had genetic evidence of inbreeding, but the malformed sperm is the first evidence that inbreeding manifests itself in the reproductive system.

“This is a serious problem for an animal that is already locally endangered,” said lead study author Audra Huffmeyer, a UCLA postdoctoral researcher who studies large cat fertility and is a National Geographic Explorer. “It’s pretty strict.”

The researchers said the results make the need for wildlife crossings more urgent, structures that allow the mountain lions and other animals to migrate further and find a larger pool of potential mates. Mountain lions – also known as pumas – are a lead species, making them a leading indicator that inbreeding could soon create problems for other species in the Santa Monica and Santa Ana mountains, the authors said.

The California Department of Transportation has plans to break ground for one such wildlife crossing, a bridge over the Ventura (101) Freeway in Agoura Hills, in early 2022, thanks to a mix of public and private funds.

Biologists and land managers hope this project will lead to more crossbreeding. Initial plans are being drawn up for a possible structure over Interstate 15 in Riverside County.

The latest study draws on the work of scientists from UCLA, the National Park Service’s Santa Monica Mountains National Recreation Area, and the UC Davis Wildlife Health Center. Both the NPS and UC Davis are conducting long-term studies of Southern California’s mountain lion populations, which are currently tracking 17 cats.

Last year, the research team identified nine adult males from the Santa Monica and Santa Ana lines with signs of inbreeding, including early indications of decreased fertility.

Their results are similar to the signs of severe inbreeding seen in most Florida panthers early in the 1990s, including kinked tails, undescended testicles, and teratospermia (60% or more abnormal sperm), Huffmeyer noted. The panther population in Florida did not recover until the introduction of the mountain lion from Texas.

“The Florida panthers were also highly isolated and highly inbred, so the fact that we are seeing the same traits in our mountain lion population is alarming,” she said. “If we don’t do anything to add genetic diversity to the Southern California mountain lions, we will have more males with reproductive problems, fewer kittens, and lower kitten survival rates.”

The scientists named a real risk of extinction for the mountain lions in the Santa Monica and Santa Ana mountain ranges. Once significant inbreeding depression is identified – meaning decreased fertility and reduced kitten survival – extinction is predicted within 50 years, according to the 2016 and 2019 papers that assessed population viability, which UCLA scientists, NPS, said , UC Davis, the University of Wyoming, and. belonged to the University of Nebraska.

While some mountain lions – notably the cougar called P-22 that visits Griffith Park – have successfully crossed highways, far more have been killed in the attempt.

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