Candid cameras at Jasper Ridge | April 23, 2014 | Almanac | Almanac Online |


Cover Story - April 23, 2014

Candid cameras at Jasper Ridge

Still and video cameras spy on wildlife at local biological preserve

by Story Dave Boyce | Photos courtesy of Jasper Ridge

Human trespassers used to frequent the 1,200 wild acres of the private Jasper Ridge Biological Preserve until around 2009, when a collection of heat-sensitive automatic cameras began to go up in selected areas of the preserve to monitor the movement of warm-blooded animals. The cameras showed another frequent presence that not been seen in other camera-trap projects: mountain lions.

Trespassing at the preserve, located off Sand Hill Road near Woodside, has fallen way off now that the word is out about the lions, says Trevor Hebert, an academic technology specialist at the Stanford University preserve. The frequency of homo sapiens and puma concolor sightings was "kind of a big surprise," Mr. Hebert says.

At, there are candid photos of the lions and many other animals, including skunks, great horned owls, bobcats, turkeys, possums, jackrabbits, foxes, coyotes, vultures and even an American badger. To advertise this online archive, the town of Woodside recently added a link at its Open Space Committee home page.

While there is no web-cam, there is a 24-hour live audio link next to an oak tree leaning over Searsville Lake, an area that birds appear to like, if the ubiquity of bird song heard over the link is any measure.

Preserve staff saw evidence of lions in deer carcasses and tracks, but their numbers weren't clear, Mr. Hebert says. With more than 20 cameras now providing thousands of photos annually, staff can recognize individual lions and monitor visits by at least one senior male and one or two females.

The auto-focusing digital cameras are Wi-Fi-enabled and automatically upload images to the preserve's server and archive, where there are now hundreds of thousands of photos, Mr. Hebert says.

Among the website's periodically updated selection of photos, plus a few videos, lions are ubiquitous, particularly at night. One video shows a couple walking single file. The lion in front ignores the camera, but the lion bringing up the rear appears to look right into it, its eyes transformed by the infrared sensor into bright dots of light.

The night remains dark to the animals. The impression of light cast in front of the camera is the action of the infrared sensor, Mr. Hebert says.

The sensors do not react to movement, but to differences in heat. Rattlesnakes and lizards may pass by, but being cold-blooded creatures, the cameras won't see them. Nor will the cameras react to blowing grass or falling leaves. It was the interest in mountain lions that drove the installation of cameras, Mr. Hebert said.

Wildlife research

While the cameras' primary role is long-term species monitoring, they also represent opportunities for research. In 2013, biology student Rachel Powell used them to study the behavior of hummingbirds at a species of flowering plant. It was known that hummingbird visits affect the presence of microbes in nectar, but, she wondered, did microbes in the nectar affect visits by hummingbirds?

As described in the preserve's 2013 annual report, Ms. Powell inoculated certain blossoms with a bacterium and tracked hummingbird preferences. The inoculations did not significantly affect their behavior, she says.

Doctoral student Eric Abelson used the cameras to look into the question of whether animals wait before using a trail recently used by another species. Do rabbits wait after a coyote has passed by? Do deer use a trail used recently by a lion? What about bobcats and coyotes? And any species and human beings?

With the help of Stanford computer scientists, Mr. Abelson streamlined the process of data-gathering by developing a program to combine already-existing data such as time stamps of images with data such as species identity and direction of travel shown in individual photos.

"The database is a goldmine of temporal relationships," he says. One early finding: mountain lions tend to use fire roads.

Listening to birds

It's been about a year since the bird-song microphone went live at Searsville Lake, Mr. Hebert says.

The spot chosen for the microphone has many places where birds can perch and features that are inviting to both predators and prey, including a leaning oak tree and snags in the water.

The sound quality is down-sampled to ease transmission over the web, about what you'd hear on AM radio, he says.

During the interview with the Almanac, Mr. Hebert reported seeing long-distance connections by listeners in Japan, China, France, Brazil and Canada, as well as many in the local area.


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