Large predators are supposed to need large spaces. This assumption has shaped decades of US conservation planning, with small wildlife refuges often dismissed as too small to matter ecologically. A new study from Stanford University just threw a wrench in that thinking.
According to the study, ‘Mammal Community Responses to Increasing Puma Activity in a Suburban Preserve,’ published in Ecology and Evolution, researchers spent nine years tracking what happened after a mountain lion began regularly passing through Jasper Ridge Biological Preserve, a roughly 1,200-acre stretch of land about 45 miles south of San Francisco. The preserve itself is too small to be able to support a resident population of mountain lions. In the nearby Santa Cruz Mountains, cats generally range over territories from 8 to 66 square miles. But this one visiting cat rearranged the entire local food web.
The paper reports that puma activity rose after 2009 in a nine-year camera-trap record spanning 17 cameras and more than 61,000 trap days, with over 38,000 independent detections overall. It also notes that mammals inside the preserve shifted their activity patterns more than those outside it, suggesting the predator’s presence was altering the community even without a resident population.
Deer disappeared, and the plants noticed
Mountain lions are increasingly showing up in trail camera images taken at Jasper Ridge between 2015 and 2020. Deer sightings on those same cameras also fell relative to previous years during that same stretch. Less deer meant less browsing pressure on the landscape, and vegetation surveys showed young oak trees and other woody plants beginning to return.
