Human activity appears to be making mountain lions in California more nocturnal.
According to a new study published in the journal Biological Conservation, mountain lions in the greater Los Angeles area that lived in regions with higher numbers of human hikers, cyclists, and joggers have become more nocturnal than those living in less busy areas.
The researchers say mountain lions' ability to change their behavior to adapt to human presence is encouraging, as it means we are more likely to be able to coexist with them in the future.
"People are increasingly enjoying recreating in nature, which is fantastic," study co-author Ellie Bolas, a Ph.D. candidate in the UC Davis Department of Wildlife, Fish and Conservation Biology, said in a statement.
"This flexibility we see in mountain lion activity is what allows us to share these natural areas together. Mountain lions are doing the work so that coexistence can happen."
Do mountain lions only come out at night?
Mountain lions—also known as cougars, panthers, or pumas—are among the largest wild cats in the United States. They are carnivorous and primarily prey on deer, elk, and occasionally smaller mammals such as raccoons or rodents.
Mountain lions are solitary and primarily crepuscular, meaning they are most active around dawn and dusk. This behavior helps them avoid heat and increases their chances of encountering prey, as many of their prey species are also active during these times.
However, mountain lions can also be nocturnal, especially in areas with significant human activity.
"Mountain lions are already nocturnal animals," Bolas told NPR. "Generally, the mountain lions that live in areas with a lot of recreation—for example, Griffith Park or the Verdugo Mountains—are less likely to be active around dawn or dusk and are more likely to be active at nocturnal times.
"During daylight, they spend about one more hour resting as compared to the mountain lions that live in more remote areas like the Santa Susana Mountains."
What hours are mountain lions most active?
The researchers used GPS trackers to monitor the movement of 22 mountain lions living in and around the Santa Monica Mountains between 2011 and 2018. They then compared this movement to human activity data from the fitness app Strava.
Interestingly, they found that the lions with more human activity in their territories didn't come out as much during dawn and dusk, instead sticking to the nighttime.
"Mountain lions in and around Los Angeles were more nocturnal and less crepuscular in areas of high recreational activity," the researchers wrote.
Some cats were more nocturnal than others, with the males P41 and "Hollywood Cat" P22 being the two most nocturnal lions in the study. Both of these males had small territories containing high levels of recreation and were surrounded by human development.
Female mountain lions showed a different response to human activity, however, as they were less prone to increasing their nocturnal habits than the males. The least nocturnal lion in the study was female P13.
"Male mountain lions are a source of mortality for females and dependent kittens, and females in this system show evidence of avoiding habitats used by males," the researchers wrote. "Diel activity of female mountain lions may be constrained by avoiding males such that they do not exhibit as strong of a response to humans."
These results are similar to previous studies that found other species of mammal around the world are also becoming more nocturnal due to human activity: One study published in the journal Science in 2018 found that deer, coyotes, tigers, and wild boar alike were all shifting their patterns to avoid us.
"These results are really important in that they show how humans may be affecting wildlife in less obvious ways than killing them with vehicles," Seth Riley, chief wildlife ecologist for Santa Monica Mountains National Recreation Area, said in the statement.
"The study also continues to drive home the amazing fact that a population of a large felid predator persists in one of the largest urban areas in the world. That would not be possible if mountain lions weren't able to adjust to human activity in ways like this."
Do mountain lions attack humans?
Mountain lions occasionally attack humans, but such incidents are extremely rare. They might attack if they feel cornered or threatened, especially if they're protecting cubs. Additionally, a mountain lion that becomes accustomed to humans due to feeding or frequent encounters might lose its natural fear and act aggressively.
Between 1890 and 2004, there were 88 reported attacks on humans across North America, which resulted in a total of 20 deaths.
When two brothers were attacked by a mountain lion in California in March, killing one of them, it marked the first death by a mountain lion in Northern California in 30 years.
According to the researchers, people can avoid encountering mountain lions by avoiding their territories at dawn and dusk and being careful while driving at night, as they are becoming more active during that time.
"Even something as innocuous as recreation can add to these other stressors we're bringing into their lives, potentially by altering the amount of energy they have to expend for hunting and other needs," Bolas said. "But we can feel a sense of optimism that they are flexible in the timing of their activity. Coexistence is happening, and it's in large part because of what mountain lions are doing."
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References
Bolas, E. C., Pingatore, A. D., Mathur, M., Blumstein, D. T., Sikich, J. A., Smith, J. A., Benson, J. F., Riley, S. P., & Blakey, R. V. (2024). Human recreation influences activity of a large carnivore in an urban landscape. Biological Conservation, 110812. https://doi.org/10.1016/j.biocon.2024.110812
Gaynor, K. M., Hojnowski, C. E., Carter, N. H., & Brashares, J. S. (2018). The influence of human disturbance on wildlife nocturnality. Science, 360(6394), 1232–1235. https://doi.org/10.1126/science.aar7121
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