Southern California Pumas Threatened

Santa Monica female P-13 on a kill, courtesy NPS

The intensity of development in the Los Angeles metroplex is affecting the genetic diversity of the region's remaining mountain lions (Puma concolor). UC Davis scientists carried out genetic sampling of 97 cougars across Southern California. Cougars living in the Santa Ana Mountains are living in genetically isolated areas and have lower genetic diversity from every other habitat in the state. The reason for this isolation is the Santa Anas are a green island awash in human urbanization. Twenty million humans surround the mountains linked to the Peninsular Range to the east only by a narrow wildilfe corridor. Unfortunately pumas avoid this corridor because it crosses a ten lane highway, I-15, hardly attractive habitat for mountain lions. Vehicle collisions are the leading cause of death in Santa Ana's cougar population. The samples indicate there has been a genetic bottleneck for the last eighty years or so, corresponding to intensive urbanization of the region. Only one lion in ten years is known to have crossed the I-15 from the east into the Santa Ana mountains. He mated successfully, injecting new DNA into the population. Such audacious crossbreeding occurs too infrequently for continued population viability.

Inbreeding is also threatening the health of lions in the Santa Monica Mountains. A study by National Park Service scientists shows that the 101 Freeway has caused a similar restriction in the movement of these cougars resulting in a higher proportion of pumas dying in conflicts with other pumas. P22 is the most famous lion in the Los Angeles area because he managed to cross two freeways and lives now in Griffth Park, but without available females to mate. He is a genetic deadend. No lion has been known to successfully leave the Santa Monicas and breed. P12 crossed into the Santa Monicas from the north and his bold legacy is reflected in the genetic structure of the isolated population. These two Southern California puma populations have among the lowest genetic diversity of lions studied, approaching that of the highly endangered Florida panthers. The Florida panther population was stabilized by the introduction of females from outside the state at the cost of millions. Such relocation projects are controversial both from a cost and biological standpoint. Caltrans has applied for $2m in federal funds to construct a wildlife bridge across Hwy 101 near Liberty Canyon expected to cost $10m. These puma studies show roads and other human development have definite adverse impacts on wildlife that can be measured in their DNA.