The hidden wildlife of Jasper Ridge
This is a guest blog from Trevor Hebert, who is the Academic Technology Specialist at Jasper Ridge Biological Preserve, where he monitors 20 wireless camera traps. He tells us a little about the project, what animals turn up on the cameras, and how Jasper Ridge uses them to provide a window on both the animals and the ecosystem…
One of the best parts of my day as technology specialist at Stanford University’s Jasper Ridge Biological Preserve is reviewing photos that have been transmitted overnight from the 20 wireless camera traps placed throughout the preserve’s 481-hectares of forests, grassland, and riparian areas.
The preserve’s rich and diverse habitats are home to many species of animals and plants found in the Santa Cruz Mountains and San Francisco Peninsula – including a few that are rare and endangered.
On any given day I might see coyotes, mountain lions, bobcats, wild turkeys, black-tailed deer, gray foxes, jackrabbits, skunks, and the occasional red-shouldered hawk or golden eagle landing in front of a camera.
My involvement with camera trapping at Jasper Ridge initially started as a proof-of-concept project for wireless sensor deployment and remote research data gathering, as we were then in the early planning stages of building a preserve-wide wireless networking infrastructure.
We felt experience with different types of wireless equipment would help inform our networking technology decisions.
But we were also interested in how the digital, wireless camera traps would compare to the 35mm film cameras used in a previous camera trap study at the preserve.
With the 35mm cameras, people frequently had to go out to the camera installations and change film and batteries. We wondered: were these frequent human visits to the camera sites influencing animal behavior, keeping away the more wary creatures?
The 35mm cameras also made an audible click and used a visible flash at night, both of which probably also reduced the chances of photographing more elusive animals such as coyotes and mountain lions.
During two years of deployment, the 35mm cameras in the previous study had captured no pictures of mountain lions and relatively few coyotes.
In contrast, the wireless digital cameras can run autonomously for long periods of time using solar panels to keep batteries charged. They also wirelessly transmit photos back to the office as they are taken.
To see if these cameras might get different results, we set up two wireless digital camera traps in 2009. From the outset, numerous coyotes were photographed regularly.
Even more exciting, within months the wireless digital cameras transmitted the first pictures of mountain lions ever taken at Jasper Ridge.
Over the years there had been many reports of mountain lion scat, scrapes, and tracks, as well as deer carcasses that were likely mountain lion kills, but no photos or confirmed sightings by individuals.
There is still some debate as to why the previous camera trap project captured no photos of mountain lions and relatively low numbers of coyotes. While the noise of the 35mm mechanical cameras and regular human presence at the camera installations seems to be a likely explanation, we can’t rule out other factors.
The current deployment of wireless digital cameras does not replicate the camera site selection of the previous study.
Instead, it favors placement of cameras on trails, roads and probable routes of animal movement, whereas the previous study used a grid to evenly space the 35mm cameras throughout the preserve.
So it is possible that mountain lions and coyotes spend the majority of their time traveling along established routes and therefore would be rarely photographed at off-trail locations.
It may be worth replicating the original study at some point. A National Science Foundation grant in 2009 allowed us to buy an additional 18 wireless camera traps, significantly expanding coverage at the preserve.
Based on the numerous photos of mountain lions at Jasper Ridge transmitted by the cameras, it is apparent that mountain lion visits are fairly common and regular.
One outcome of this new knowledge was a review by the Jasper Ridge Advisory Committee that identified ways the preserve can begin to use the mountain lion data, such as coordinating new research and reevaluating safety training for the JRBP community.
While interest in understanding the distribution, population size and activities of mountain lions in our area has provided some of the impetus behind the expansion of our camera trap network, the cameras are providing a window onto the lives of many different animals who live here.
I particularly enjoy seeing the yearly life-cycle of our resident black-tailed deer documented by the camera traps: When the fawning season typically begins, peaks and ends each year; when the fawns lose their spots; when the bucks’ antlers grow and lose their velvet; when rutting season starts; and when the antlers drop.
The camera traps have also documented interesting feeding behaviors, such as the deer eating lace lichen in winter when other forage is scarce.
Probably the rarest animal we have at the preserve is the American badger – I’ve only had a few photos in 4 years.
While the badger is not endangered in North America as a whole, it has not done well locally due to habitat fragmentation, its poor road crossing abilities, and historical trapping by humans.
Prior to the camera trap photos, we really had no idea of the status of badgers here. We now know they are present locally, but in low numbers and may need special help to survive in our area.
While we have no endangered mammals here at JRBP, camera trap photos could help us monitor the threat posed by rodenticides, which end up in the bodies of small predators such as bobcats and coyotes after they ingest poisoned rodents.
If such poisoning is an issue locally, the relative numbers of bobcats appearing in the camera trap photos may show a decline. In this regard, the camera traps are a window on the health of our local ecosystem.
You can find out more about Trevor’s work on the camera trap project at Jasper Ridge Biological Preserve here.