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Mountain lions actively avoid artificial light

In Southern California’s bustling urban environment, mountain lions navigate a landscape illuminated by constant city lights. Recent research from the University of California, Davis, reveals that these big cats actively avoid areas with artificial light, a behavior persisting even during daylight. 

This new insight, published in the journal Philosophical Transactions of the Royal Society B, adds to the growing list of conservation challenges for mountain lions in the region, where their survival is increasingly precarious.

Artifical light impacts

The study’s implications are significant for the conservation of mountain lions and the design of wildlife crossings. The researchers provided design guidance for minimizing light impacts on the Wallis Annenberg crossing over U.S. Highway 101 and a proposed Interstate 15 crossing near Temecula. 

Senior author Fraser Shilling, director of the UC Davis Road Ecology Center, emphasized the impact of artificial light.

“Well-lit streets, neighborhoods, and commercial areas will reduce and fragment the areas available to mountain lions to move around,” said Shilling. “It’s not just the outsized human footprint that is squashing lion habitat, but the extended glow from that footprint, too.”

How the research was conducted 

The experts analyzed the habitat preferences of 102 radio-collared mountain lions monitored across California from 2001 to 2022. 

This data, collected by the UC Davis School of Veterinary Medicine, the California Department of Fish and Wildlife, and other partners, helped the team assess the influence of artificial lights, sky glow, and moonlight on mountain lion distribution.

What the researchers learned 

The findings were striking. While sky glow and moonlight did not deter mountain lions, nearby ground-based artificial light did. 

Study lead author Rafael Barrientos is an ecologist with Universidad Complutense in Madrid, Spain, and visiting scientist at the Road Ecology Center.

“Overall, we found that mountain lions try to avoid zones lit artificially, possibly to avoid interactions with humans,” said Barrientos. “This can have cascading effects on the redistribution of the species in the region, as well as the benefits wildlife provide in this ecosystem.”

Study significance 

Mountain lion expert and co-author Winston Vickers, from the UC Davis School of Veterinary Medicine, further highlighted the significance of these findings for wildlife crossing structures. 

“Our research has shown that even when structures exist to allow mountain lion passage under freeways, the light and noise can deter mountain lions from use of these safe crossing structures,” explained Vickers.

These findings highlight the need for careful planning and innovative solutions in urban development and wildlife conservation. As Southern California continues to grow, ensuring the coexistence of human expansion and the natural world will require a nuanced approach, particularly in managing light pollution and its effects on local wildlife.

SoCal mountain lions

Mountain lions, also known as cougars or pumas, are present in Southern California, where they live primarily in the mountain ranges and foothills. These large cats require large territories for hunting and often come into conflict with human development as urban areas expand into their habitats. 

In Southern California, the fragmentation of their habitat due to highways and development has led to a number of conservation efforts aimed at protecting these animals. This includes tracking individual lions, promoting genetic diversity, and creating wildlife corridors to connect fragmented habitats. 

There have been instances of mountain lions entering residential areas, which typically leads to wildlife officials intervening to ensure the safety of both the animals and the residents. Conservationists continue to monitor their populations and advocate for measures to preserve their ecosystems amidst the challenges they face.

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