Wildlife Cameras Take Stock of Rancho Corral de Tierra’s Animals

A mountain lion caught by a wildlife camera at Rancho during the 2014 Golden Gate National Parks BioBlitz. Image from the National Park Service's page.

It's hard for a park to protect wildlife habitat and sensitive species when nobody is quite sure what lives there — especially when so many animals are experts at avoiding people. That was the challenge facing National Park Service biologists at Rancho Corral de Tierra, which joined Golden Gate National Recreation Area in 2011. In August 2023, they launched the San Mateo Wildlife Inventory to find out, using wildlife cameras and help from the community.

The place

• About 20 miles south of San Francisco, Rancho covers nearly 4,000 acres, from 60 feet above sea level near the coast to more than 1,700 feet atop Montara Mountain.
• Its habitats range from dominant coastal scrub to streamside woodlands, freshwater wetlands, coastal grasslands, non-native forests and manzanita chaparral.
• It connects to the San Francisco Public Utilities Commission watershed and to state and county parkland, and on to other protected areas of the San Francisco Peninsula and Santa Cruz Mountains.

The cameras

Modeled on One Tam's successful camera-based Marin Wildlife Watch project:

• 24 standard cameras on a 0.5-kilometer grid, spanning different habitats, elevations and levels of development, placed on game trails and habitat edges that mammals are likely to use. They work best for medium and large mammals.
• 10 close-up cameras for reptiles and amphibians, set up with drift fences that funnel small animals toward the lens — a method from the California Department of Fish and Wildlife.

NPS wildlife biologist Rachel Townsend sets up a camera in Rancho's upper elevations. NPS / Eric Wrubel.

The project is only about wildlife. Cameras are placed away from trails, but because they're triggered by motion and heat they may catch visitors and pets. The photos are not used to identify people or their pets.

Golden Gate staff and interns with a newly built reptile-and-amphibian camera: the camera is in the green box, and the drift fence funnels animals toward it. NPS / Darren Fong.

From photo to data

1. Memory cards are collected every three months and uploaded to a cloud database.
2. Artificial intelligence software suggests an identification for each image.
3. People verify each identification — and the project is recruiting community scientists to help, with training and, perhaps, group cataloging parties.
4. The team then builds a species list, calculates detection rates, estimates occupancy for common species, watches sensitive species' numbers, locations and habitat, and — over years — tracks biodiversity trends.

Goals

• Inventory mammals over 1 kilogram and reptiles and amphibians.
• Learn about rare and sensitive species.
• Track abundance and diversity over time.
• Detect invasive species such as feral pigs.
• Engage the community with photos of rarely seen wildlife and invitations to help identify them.

Mountain lions

Earlier, smaller camera efforts and reports from neighbors show mountain lions live at Rancho. As apex predators, they are important to land ecosystems, and the regional population — the central coast Ecologically Significant Unit — had recently become a candidate for listing under the California Endangered Species Act. They can also frighten people and endanger wandering pets. What the cameras reveal about their activity will help shape coexistence outreach.

Sources

Based on "Capturing Biodiversity on Camera at Rancho Corral de Tierra," by wildlife ecologist Bill Merkle and biologist Eric Wrubel, Golden Gate National Recreation Area, with science communication specialist Jessica Weinberg McClosky, San Francisco Bay Area Network, Bay Area Nature & Science Blog, National Park Service, September 2023; a work of the United States government in the public domain.