LA's Isolated Mountain Lions Are Developing Kinked Tails Due To Inbreeding

An ambitious wildlife bridge could be the key to their survival. National Park Service/SMMNRA

Los Angeles is home to a population of mountain lions who have become so cut off from other cats that their tails are changing as the result of inbreeding. Concern for their wellbeing as the genetic pool closes has been mounting for some time, and new research into the prevalence of this tail malformation serves as confirmation that the animals are at risk of becoming sterile if nothing is done to increase diversity within the population.

Locked in by the dense network of roads surrounding the Santa Monica mountains, the mountain lions in LA have the lowest genetic diversity of any lion population in the western United States. Loss of genetic diversity is a catastrophic event within a population, as genetic diseases become more prevalent and lead to malformations and sterility in future generations. The effects of inbreeding are already being seen in the L-shaped kinks at the end of the lions’ tails and some males are exhibiting cryptorchidism, a malformation that prevents one or both testes from descending in adulthood.

As inbreeding is on the rise, so too are the kinks in the lions' tails. National Park Service/SMMNRA

Research has been looking at the lions for the past 18 years, but a recent announcement from the Santa Monica Mountains National Recreation Area (SMMNRA) marked the first time physical malformations had been discovered and directly linked to the population’s inbreeding depression. The emergence of deformities shares parallels with the loss of genetic diversity in mountain lions in Florida, eastern USA.

“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,” said Seth Riley, chief of the wildlife branch for the SMMNRA. The same type of kinked tails and cryptorchidism were also seen in these animals, but the crucial difference is that, unlike Florida, LA’s mountain lions have options as there are other large populations in the West.

Four female cubs found in the Santa Monica Mountains are thought to be the product of inbreeding. National Park Service/SMMNRA

As such, Riley believes connectivity is the key to turning things around. He suggests that rather than importing mountain lions from other areas it would be better to establish wildlife crossings to bring populations together. The bridge could connect populations of wildlife beyond just mountain lions from south of the 101 Freeway to those in other natural areas to the north in the Simi Hills, the Santa Susana Mountains, and in Los Padres National Forest. If funding efforts are successful, the ambitious project will be the first wildlife overpass established in such a large metropolitan area and will begin construction in 2021.

“The truth is that we want to build that connectivity not just for the mountain lions, but for all of the wildlife,” Riley said.


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