Southern California cougars often make the headlines with their oh-so-cute kitten litters, but a UCLA-led study suggests that a lack of genetic diversity would soon make it much harder for these mountain lions to reproduce.
Scientists tracking two local mountain lion populations, one in the Santa Monica Mountains and another in the Santa Anas, have identified the first reproductive signs of inbreeding among these groups, cut off from other puma populations – and hence breeding opportunities – by busy highways.
The animals averaged a whopping 93% abnormal sperm rates, while some also showed physical signs of inbreeding, such as deformed tails or testicular defects. 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 endangered locally,” said lead study author Audra Huffmeyer, a UCLA postdoctoral researcher who studies large cat fertility and one National Geographic Explorer. “It’s pretty heavy.”
The study, currently Available online and slated for publication in the print edition of Theriogenology magazine in January 2022, heightened the urgency of the need for wildlife crossings, structures that would allow mountain lions and other animals to continue to migrate and find a wider pool of potential partners, the said Researcher. Mountain lions, also known as pumas, are a flagship species, making them a leading indicator that inbreeding could soon be a problem for other wildlife species in the Santa Monica and Santa Ana mountains, the researchers said.
Current research draws on the work of scientists from UCLA, the Santa Monica Mountains National Recreation Area of the National Park Service, and the UC Davis Wildlife Health Center. Both the NPS and UC Davis are conducting long-term studies of Southern California mountain lion populations, with a total of 17 cats currently being tracked.
Tracking down the signs of inbreeding
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. The scientists took semen samples from five pumas who died from other causes such as rat poison and car collisions. (Although the researchers want to get these samples from live mountain lions, it’s not surprising that this is a complicated proposition.) They found that each had very high levels of abnormal sperm, which together gave a very high abnormal sperm rate of 93% . One of the five also had testicles of dramatically different sizes.
The researchers also found other tell-tale physical manifestations of inbreeding in live cougars: four had kinks in their tails, including one with even testicular descent. Both mountain ranges included at least one mountain lion with a malformed tail and one with abnormal sperm.
These 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.”
Ultimately, the mountain lions in the Santa Monica and Santa Ana areas are at real risk of extinction. While they haven’t seen any evidence, extinction is predicted within 50 years once scientists detect significant inbreeding depression – meaning decreased fertility and decreased kitten survival – with a median extinction of 12-15 years, according to 2016 and 2019 Population Viability Assessment Papers, which included scientists from UCLA, NPS, UC Davis, the University of Wyoming, and the University of Nebraska.
“That is why this recent discovery of physical manifestations of inbreeding is so significant,” said Seth Riley, director of the Santa Monica Mountains National Recreation Area wildlife division and researcher and associate professor at UCLA. “We are not yet seeing the decline in survival, reproduction, and physical condition that you have seen in Florida, but seeing these signs is a major concern and a potential harbinger of more, more serious, problems. We haven’t seen a noticeable decrease in kitten litters, but it could be a little early. “
Find a solution: wildlife crossings
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. For years, conservationists have advocated the construction of wildlife crossings that help populations of pumas and other animals cooped up from roads connect with populations from which they have been largely isolated for generations, Riley said.
The California Department of Transportation has planned the groundbreaking ceremony for such a crossing in early 2022, a Wildlife bridge on Highway 101 in Agoura Hills in northwest Los Angeles County, thanks to a mixture of public and private funding. Biologists and land managers hope this project will lead to more crossbreeding. In fact, initial plans are being made for a possible structure over Interstate 15 in Riverside County.
Crossbreeds, the researchers say, help all local animal species increase their genetic mix and, when possible, are preferable to the Florida scheme of transporting mountain lions to limited local habitats, which is not a long-term solution and can often be fatal. for relocated animals.
For now, researchers will continue to monitor how the newly discovered fertility problems affect mountain lion breeding, while keeping an eye out for a possible decline in the number of kitten litters and kitten survival rates.
“If we do nothing for genetic diversity, the end is near,” emphasized Huffmeyer. “That sounds dramatic, but we saw that.”
The research was also carried out by senior author Robert Wayne, a distinguished professor of ecology and evolutionary biology at UCLA; Winston Vickers, director of the Mountain Lion Project at UC Davis Wildlife Health Center; and NPS field biologist Jeff Sikich.