Researchers at Stanford's Jasper Ridge Biological Preserve often encounter signs of mountain lion activity, from lion scat to the occasional deer carcass covered with leaves. But few have actually caught a glimpse of the shy feline.
Now, images captured by remote wildlife cameras confirm that mountain lions (also called pumas or cougars) make regular visits to Stanford's 1,189-acre preserve in the hills five miles west of the main campus.
Since September 2009, a network of motion-activated infrared cameras has recorded more than 40 photographs and videos of mountain lions in different areas of the preserve. Most of the images were captured between dusk and dawn, occasionally along trails frequented by docents, researchers and staff. However, an analysis of 30 lion photos from summer 2010 suggests that one animal triggered all of the images.
"The cameras are running 24 hours a day," said Trevor Hebert, Jasper Ridge's data manager. "Basically, anything that moves in front of them that's alive will trigger a picture."
The photos suggest a seasonal pattern of lion activity over the last two years, Hebert said, with more visits occurring during the dry months from May to September.
"One of the very encouraging things about all of the mountain lion pictures is that we know that we essentially have an intact ecosystem with the top predator actively killing deer," Hebert said. "We weren't always sure that was the case."
An upsurge in mountain lion photos last spring led the Jasper Ridge advisory committee to recommend a review of preserve policy. In June 2010, Jasper Ridge staff invited a group of Stanford students to serve as academic consultants on the review.
The students were part of the Rising Environmental Leaders Network, a pilot project of Stanford's Woods Institute for the Environment designed to give postdoctoral scholars and graduate students an opportunity to participate in a real-world consulting experience. The project was modeled after the Woods Institute's Leopold Leadership Program. Nicole Ardoin, a member of the Jasper Ridge advisory committee, served as the faculty leader.
"This was a test case -- an opportunity to engage faculty, postdocs and graduate students in project-based learning with a risk assessment/management component," said Ardoin, an assistant professor of education and center fellow at the Woods Institute.
The consulting team consisted of five students from different academic disciplines: graduate student Lena Perkins (mechanical engineering) and postdocs Kye Epps (soil science), Steve Litvin (marine ecology), Scott Loarie (landscape ecology) and Mike Papenfus (economics). The students were asked to assess the risk of a human-lion encounter in Jasper Ridge and to explore new opportunities for mountain lion research and conservation in and around the preserve.
In July 2011, after analyzing the photographic data and conferring with experts, the student team submitted its findings and recommendations to the Jasper Ridge advisory council. The report concluded that mountain lions are probably roaming the preserve about 24 percent of the time, but that "there are likely at most only one male, one female and possibly several cubs whose territory includes the preserve."
An adult male lion can weigh 200 pounds and stretch 9 feet from the nose to the tip of the tail. Despite the mountain lions' size and remarkable hunting prowess, humans have little to fear: "Based on historical statewide data, the annual risk of being attacked by a mountain lion in Jasper Ridge is 1 in 10 million," the authors wrote.
"We humans present a greater risk to mountain lions than mountain lions present to us," added Epps, a co-author of the report, which is now available online.
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