Southern California mountain lions show early effects of inbreeding on reproduction

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The mountain lion known as P-81, pictured here, is one of the first in the Santa Monica Mountains to exhibit a tail defect.
NPS photo

Jan. 8, 2022 – Alison Hewitt – Southern California cougars are often in the news with their litters of cute kittens, but a UCLA study suggests these pumas may soon have a much harder time mating in due to a lack of genetic diversity.

Scientists tracking two local populations of cougars, one in the Santa Monica Mountains and the other in the Santa Anas, have identified the first reproductive signs of inbreeding among these groups, which are cut off from other cougar populations – and therefore breeding options – by busy highways. .

The animals averaged an abnormal sperm count of 93%, while some also showed physical signs of inbreeding, such as deformed tails or testicular defects. Researchers have long had genetic evidence for inbreeding, but malformed sperm is the first evidence that inbreeding occurs in the reproductive system.

“This is a serious problem for an animal that is already endangered locally,” said lead author of the study, Audra Huffmeyer, a postdoctoral researcher at UCLA who studies fertility in large feline species and is a National Geographic explorer. “It’s pretty harsh.”

The study, currently available online and scheduled for publication in the January 2022 print edition of the journal Theriogenology, adds an additional urgency to the need for wildlife crossings, structures that would allow mountain lions and d ‘other animals to wander further and find a larger pool of potential mates, the researchers said. Mountain lions, also known as cougars, are a flagship species, making them a leading indicator that inbreeding could soon cause problems for other wildlife in the Santa Monica and Santa Ana mountains, the researchers explained.

The current research builds on the work of scientists at UCLA, the Santa Monica Mountains National Recreation Area of ​​the National Park Service, and the UC Davis Wildlife Health Center. The NPS and UC Davis are conducting long-term studies of Southern California cougar populations, currently tracking 17 cats in total.

Monitoring for signs of inbreeding

Over the past year, the research team has identified nine adult males from the Santa Monica and Santa Ana ranges showing signs of inbreeding, including early signs of reduced fertility. Scientists took semen samples from five cougars who died of unrelated causes, such as rat poisoning or car crashes. (While the researchers are keen to get these live mountain lion samples, this is unsurprisingly a complicated proposition.) They found that each had very high levels of abnormal sperm, with an average rate of 93%. abnormal sperm count on average. One of the five also had very different sized testicles.

The researchers also found other revealing physical manifestations of inbreeding among living cougars: four had bent tails, one of which also had only one descending testis. The two mountain ranges included at least one puma with a malformed tail and one with abnormal sperm.

Mountain lion twisted tail photo

The twisted tail of the P-81, a physical manifestation of inbreeding. This same male cougar was found to have an undescended testicle, a condition known as cryptorchidism. NPS photo

These findings are similar to the signs of severe inbreeding seen early in most Florida panthers in the 1990s – including crooked tails, undescended testes, and teratospermia (60% or more of abnormal sperm), Huffmeyer noted. . The Florida panther population did not recover until the introduction of Texas pumas.

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

Ultimately, the risk of extinction of pumas in the Santa Monica and Santa Ana chains is real. Although they haven’t seen any evidence yet, once scientists start to find significant inbreeding depression – which means decreased fertility and kitten survival – extinction is expected to occur in the kittens. 50 years old, with a median time to extinction of 12 to 15 years, according to 2016 and 2019 papers assessing population viability that included scientists from UCLA, NPS, UC Davis, University of Wyoming and the University of Nebraska.

“This is why these recent findings of physical manifestations of inbreeding are so important,” said Seth Riley, chief of the wildlife branch at Santa Monica Mountains National Recreation Area and researcher and adjunct associate professor at UCLA. “We are not yet seeing the declines in survival, reproduction and fitness that they have seen in Florida, but seeing the signs is a major concern and a potential harbinger of more serious problems. We haven’t seen a noticeable drop in kitten litters yet, but it may be a bit early. “

Find a solution: wildlife passages

While a few pumas – especially the cougar known as P-22, which frequents Griffith Park – have successfully crossed the freeways, many more have been killed trying to do so. For years, environmentalists have lobbied for the construction of wildlife crossings that will help populations of cougars and other animals parked on the roads connect with populations from which they have been largely isolated for generations, said Riley.

Mountain lion kittens

Kittens from a local population of cougars followed by the National Park Service and UCLA (2015). NPS photo

The California Department of Transportation has scheduled one such crossing, a wildlife bridge over Highway 101 in Agoura Hills, northwest Los Angeles County, to be opened in early 2022. , through a mix of public and private funding. Biologists and land managers hope this project will lead to more crossings. In fact, the first plans are being formulated for a possible structure on Interstate 15 in Riverside County.

Crossbreeds, the researchers say, help all local animal species increase their genetic mix and, where possible, are preferable to Florida’s program of transporting mountain lions to local, circumscribed habitats, which is not. a long-term solution and can often result in mortality. for displaced animals.

For now, researchers will continue to monitor how newly discovered fertility issues affect cougar reproduction, closely monitoring potential decreases in kitten litters and kitten survival rates.

“If we don’t do anything to add genetic diversity, the end is near,” Huffmeyer said. “It sounds dramatic, but that’s what we saw.”

Senior author Robert Wayne, distinguished professor of ecology and evolutionary biology at UCLA, also contributed to the research; Winston Vickers, director of the Mountain Lion Project at UC Davis Wildlife Health Center; and NPS field biologist Jeff Sikich.
Source: UCLA

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