Los Angeles cougars are threatened by inbreeding

In a recent study published in the journal Theriogenology, researchers found that nine cougars living in the Los Angeles area had either very high levels of abnormal sperm or tail malformations, signs of a severe lack of genetic diversity. . Two males also had testicular abnormalities, also recognized as being due to inbreeding. The Los Angeles area has only a few dozen cougars, so a large portion of the cat population is affected.

Several of these indications, observed between December 2019 and December 2020 in connection with classical research work and autopsies performed on animals affected by vehicles, have been observed in felines living in the metropolitan area and its outskirts. Prior to this study, only one specimen with a deformed tail was observed in the area. That was in 2019.

“We’ve reached a turning point in genetics,” said Audra Huffmeyer, a postdoc researcher in conservation biology at the University of California, Los Angeles and National Geographic Explorer.

In order to survive in the long run, a large number of cougars must be able to move freely between the two most isolated areas where the animals live: the Santa Monica mountain range, located northwest of the city, and the one in Santa Ana, southeast.

But all is not lost for the cats. A new ecoduct should therefore soon be built over Route 101 so that the animals can cross the axis without danger. The groundbreaking ceremony for the project was held on April 22 (Earth Day) and the bridge is expected to open in 2025.

“I think this passage can help prevent the extinction” of the Santa Monica population, “said Seth Riley, co-author of the study and wildlife ecologist for the United States National Park Service, who also teaches at UCLA. “We are convinced that it will benefit all wildlife, especially cougars, by improving the connection.”


Cougars were once found all over most of the contiguous United States. But with hunting, widespread and supported by the government, their range shrank so that it was limited to the western part of the country in the mid-20s.and century. Big cats, also known as cougars or mountain lions (whose scientific name is Puma concolor)are also well established in Central and South America.

Florida Panthers, recognized by the U.S. government as a subspecies of the puma, have managed to survive in the wilds of southern Florida. Cut off from any other population, they quickly suffered from inbreeding. The animals then began to show high incidences of sperm, testicle and tail malformations. The introduction in 1995 of eight female Texas cougars, five of which bred with Florida panthers, increasing the number of the latter and improving their genetic diversity, made it possible to save the subspecies.

In the 1980s, before the genetic rescue operations, three-quarters of the Florida panthers examined had tail defects, and more than half had testicular defects. That was far more than what is currently seen in Southern California, says researcher Dave Onorato of the Florida Fish and Wildlife Conservation Commission, who did not participate in the study.

He adds, however, that scientists “are beginning to observe these signs” in Los Angeles, “and it certainly justifies ringing the alarm bells.”


Seth Riley and many collaborators have been studying cougars in the Los Angeles area for 20 years.

To conduct their most recent study, Audra Huffmeyer and her colleagues collected observations of felines in the California metropolitan area. About ten individuals live in the Santa Monica mountain range, and up to 12 specimens live in Santa Susanas, located north of the city and the intersection of Route 101. About twenty others live in the Santa Ana chain, southeast of Los Angeles. Finally, a larger population has found their home in the country in the eastern Peninsular Ranges, say Winston Vickers and Justin Dellinger, biologists at UC Davis School of Veterinary Medicine’s Wildlife Health Center.

Between December 2019 and December 2020, researchers using camera traps observed three animals with a tail defect that belonged to the populations of the Santa Monica and Santa Susana mountain ranges. A fourth individual that scientists examined in the field in the Santa Monica Mountains also had a deformed tail and a non-submerged testicle.

Audra Huffmeyer also performed a sperm quality analysis on five felines that were shot, poisoned to death by rats or hit by vehicles. All were from the people of Santa Monica, Santa Ana and the Eastern Peninsula. On average, 93% of puma’s sperm showed a malformation. A very high number, which is similar to what was observed in Florida panthers before the start of genetic rescue operations, emphasizes Dave Onorato.


To increase genetic diversity, a larger number of felines must be able to circulate between these isolated populations. On April 22, work began on the Wallis Annenberg ecoduct, a project led by a consortium of environmental groups. At a cost of $ 90 million (approximately 85 million euros), the bridge will span the ten lanes of the 101 Freeway, thus allowing cougars, coyotes, deer and other animals to reach the Santa Monica or Santa Susana mountain range. .

Agoura Hills, an area of ​​uneven terrain where wildlife naturally grazes, was chosen to host the project. Scientists are confident that wildlife will use the bridge, especially species that need a large territory, such as cougars.

But to save the felines, other ecoducts will be needed, especially on Interstate 15, which separates the Santa Ana mountain range from the puma populations established in the eastern part of the region. According to Audra Huffmeyer, one day it may become necessary to transfer cougars from other parts of the country to improve the genetic diversity of Los Angeles’ cat populations. But this is a last resort solution.

For the time being, the researchers are eager for the work on the ecoduct to be completed and for the cougars to use it.

“It only takes a few copies to cross it to make a big difference,” says Seth Riley.

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