Bobcat Habitat Connectivity Study
In a race against urban sprawl, researchers are increasingly on a mission to safeguard the precious threads of ecological connectivity weaving through crucial mountain ranges. The strategy? Pinpoint vital connectivity corridors, or “last chance” corridors, and shield the remaining natural havens from impending development devastation. This project harnessed cutting-edge data—precise 5-minute tracking of bobcat movements—to strategically guide land acquisitions aimed at supercharging conservation efforts.
Set against the backdrop of bustling San Jose, California, urban encroachment poses a dire threat, ready to sever the Santa Cruz Mountains from the neighboring Diablo and Gabilan Mountain ranges. These mountains, a vibrant biodiversity hotspot, shelter countless species on California’s watchlist of conservation concern. Yet, the relentless march of urbanization sprawling from the cities of San Francisco, San Jose, and Santa Cruz threatens to cut them off from the Diablo and Gabilan ranges.
Here, researchers focused on just two slender “last chance” corridors that might still bridge the Santa Cruz with its neighboring ranges. Generating data not just to assess but enhance connectivity, the study fuelled a landmark conservation triumph: the acquisition of land in Coyote Valley, now steadfastly protected from commercial invasion.
Map of the study area between the Santa Cruz, Diablo, and Gabilan mountain ranges.
With these 5-minute movement data, we monitored how, where, and when bobcat crossed roads so we could determine what facilitates and deters bobcats from crossing roads. Our deep dive into the landscape included both natural features like trees, shrubs, grass, and water, and altered areas such as housing development, roads, crops, orchards, and eucalyptus. We used these landscape features to understand their influence on bobcat movement across the landscape. We didn’t stop there; we also kept tables on bobcat fatalities, both collared bobcats and those we stumbled upon unexpectedly during our research. This endeavor offered a fresh perspective on the complex interplay of nature and urban development through the eyes of one of California’s stealthiest elusive carnivores. Read the publication here.
To crack the code of ecological connectivity, we needed to view the landscape through the eyes of the landscape’s own residents. Here, we focused on bobcats– highly mobile carnivores that are relatively easy to capture. Over the course of 15-months, we captured and GPS-collared 36 bobcats. The collars collected fine-scale 5-minute movement data, and we ultimately collected nearly 700,000 GPS points over an 18-month period.
Using 5-minute movement data combined with high resolution satellite imagery, we observed that bobcats effectively moved from tree to tree or shrub to shrub as shown in the figuree above.
INTERESTING FINDINGS:
After collecting 672,000 5-minute movement GPS-locations, we learned a lot about how bobcats navigate the landscape of Central Coast California. Some of the highlights are:
When moving across a landscape of mixed grass, shrubs, and trees, bobcats prefer to move from tree to tree or shrub to shrub
Bobcats do not like agriculture- they avoided moving through areas with low-lying crops and orchards. They also do not like eucalyptus, and in fact, they prefer orchards over eucalyptus groves.
Bobcats cross roads a lot. We observed 3,333 road crossings across seven arterial roads of interest, including Highway 101. But even though Highway 101 is one of the busiest travel corridors in the entire United States, so long as there were culverts or bridges with natural vegetation on either side, bobcats regularly crossed (under) the busy 8-10-lane freeway.
Bobcats mostly died from being hit by cars or from notoedric mange, trends observed in other human-impacted landscapes in California. 94% of the bobcats we tested were exposed to common anticoagulant rat poisons. This type of poison exposure has been linked with immune dysfunction in bobcats, and likely contributed to the cases of mange deaths we observed.
CONSERVATION OUTCOMES:
Our first conservation-related objective was to prepare a report describing our research findings and recommendations for land acquisition and restoration. We submitted our report in July 2019, and within 5 months, we received news of a historic $93 million dollar deal reached to preserve San Jose’s Coyote Valley. This land deal is one of many that will occur in the Coyote Valley (found within Silicon Valley) and will ensure ecological connectivity between the Santa Cruz Mountains and the Diablo Range. More land acquisition will follow, and much of the land to be acquired is heavily impacted by intense agriculture. To ensure ecological connectivity, local land management agencies will have to restore natural vegetation to the parcels. We have also made recommendations for facilitating safe-road crossings and reducing rat poison use in the areas.
A photo of the property purchased as part of the historic land deal. The property will need to be restored with native vegetation to promote connectivity.