After mountain lion (Puma concolor, also known as puma or cougar) activity began increasing around 2012, researchers documented ripple effects through multiple species. Coyotes and deer shifted away from nighttime activity. Gray foxes expanded into niches left vacant by retreating competitors. Brush rabbits became more active in the mornings, and woody plant density jumped 64-fold over 17 years.<\/p>\n
These types of multi-level effects are called trophic cascades. The most well-known example comes from the U.S., as dramatic changes occurred in Yellowstone National Park when wolves were reintroduced to their former range in 1996.<\/p>\n
\u201cMuch like the well-documented cascade triggered by wolves in Yellowstone, we found that increasing mountain lion activity coincided with changes cascading through the food web, from deer and coyotes down to foxes, rabbits, and woody plants,\u201d lead author Chinmay Sonawane, a Stanford Ph.D. candidate, said in an email to Mongabay.<\/p>\n
\u201cThese findings provide clear, empirical evidence of the profound structural role mountain lions play,\u201d Zara McDonald, biologist and president of the Felidae Conservation Fund<\/a> who was not involved in the study, told Mongabay in an email. \u201cBy tracking the surge in [mountain lion] activity, researchers documented a direct drop in deer activity, which immediately allowed over-browsed native plants and young oak trees to recover and thrive.\u201d<\/p>\n Why the mountain lions started frequenting Jasper Ridge is unknown. One theory is that females found that the preserve was a safe place to raise their young. (A mother with kittens was spotted on camera during the study.) Whatever the reason, the animals aren\u2019t residents, they\u2019re visitors. Jasper Ridge is far too small to support its own population, but mountain lions range through the nearby Santa Cruz Mountains.<\/p>\n The Jasper Ridge story is also a story about fragmented landscapes. Mountain lions are territorial animals with enormous home ranges, sometimes spanning hundreds of kilometers. They must be able to move freely to hunt, find water, locate a mate, and escape increasingly severe climate-driven disasters, such as wildfires, drought and flooding and mudslides that follow storms. Without corridors linking these fragmented habitats, top predators will remain absent.<\/p>\n \u201cThe trophic cascade documented at Jasper Ridge only works because these cats have a way to get there. It underscores the absolute necessity of preserving wildlife corridors that link urban fringe preserves to larger wild spaces,\u201d McDonald said. \u201cIf we want resilient ecosystems with balanced wildlife and thriving native flora, we have to design landscapes that allow apex predators to move safely through them.\u201d Analysis of camera timestamps showed that during years of high mountain lion activity, several species changed their behavior. Coyotes (Canis latrans) reduced their nighttime activity by 25% and deer by 34%, according to the study.<\/p>\n Vegetation surveys conducted in 2006, 2015 and 2023 captured a dramatic increase in woody plants, including California sagebrush (Artemisia californica), iconic coast live oak (Quercus agrifolia) and poison oak (Toxicodendron diversilobum). They all flourished as deer browsing declined.<\/p>\n The study\u2019s authors caution that evidence for some links in the chain, particularly those involving foxes, rabbits and vegetation, remains preliminary. The study also could not determine whether the observed changes were driven by shifts in animal behavior, changes in population size \u2014 or both.<\/p>\n A companion study<\/a> from the same research group used the COVID-19 lockdown as a natural experiment. They found that reduced human activity at the preserve during lockdowns had minimal effects on wildlife behavior, helping to rule out people as the main driver of the observed patterns.<\/p>\n \u2018Humans are the ultimate predator\u2019<\/p>\n Despite the occasional high-profile sighting of a mountain lion in a city or suburb \u2014 like the famous P-22<\/a> in Los Angeles \u2014 the cats tend to stay far from people, and for good reason. Humans are the leading cause of mountain lion deaths<\/a>, either through hunting or vehicle collisions,the study\u2019s senior author Elizabeth Hadly, a Stanford professor emerita of biology,said in a press release.<\/p>\n \u201cHumans are the ultimate predator on almost every landscape,\u201d Hadly said. \u201cPumas are afraid of our smell and our sounds; they don\u2019t like to see us moving. Pumas use all of their senses to avoid humans.\u201d<\/p>\n According to the study, about 82% of protected areas in the U.S. are smaller than 5 square kilometers, roughly 2 square miles, making small suburban preserves like Jasper Ridge increasingly important for wildlife as urban development expands, said study co-author Rodolfo Dirzo, a Stanford professor of biology.<\/p>\n \u201cMaintaining sites where there is an entire community of animals, from predators to prey \u2026 is very important,\u201d Dirzo said in a press release. \u201cWhen one piece is missing \u2026 we will no longer have fully functioning ecosystems.\u201d<\/p>\n \u201cThis study is a powerful reminder that mountain lions are ecosystem engineers,\u201d McDonald said. \u201cProtecting pumas isn\u2019t just about saving a charismatic species. It\u2019s about safeguarding the functional health of the entire landscape.\u201d<\/p>\n Banner image of puma and cubs in Jasper Ridge in 2018 courtesy of Trevor Hebert.\u00a0<\/p>\n Citations:<\/p>\n Sonawane, C., Leempoel, K., Nova, N., Meyer, J. M., H\u00e9bert, T., Zuckerwise, A., \u2026 & Hadly, E. A. (2026). Mammal Community Responses to Increasing Puma Activity in a Suburban Preserve. Ecology and Evolution, 16(6), e73775. doi:10.1002\/ece3.73775<\/a><\/p>\n B\u00e9llo Carvalho, R., Frangos, C., Sonawane, C., H\u00e9bert, T., Hadly, E. A., & Dirzo, R. (2026). Limited changes to mammal diel activity during COVID-19 lockdown in an urban preserve. Journal of Mammalogy, 107(2), 358-367. doi:10.1093\/jmammal\/gyag012<\/a><\/p>\n FEEDBACK:\u00a0Use this form<\/a>\u00a0to send a message directly to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.<\/p>\n More to explore:<\/p>\n Pumas create nutrient-rich \u2018kill gardens\u2019 to attract prey: Study<\/a><\/p>\n \u00a0<\/p>\n Cite this articleLiz Kimbrough (2026). One mountain lion changed the food web in a California suburb, study finds. Mongabay Conservation news. DOI: https:\/\/doi.org\/10.66709\/news-322039<\/a> <\/p>\n ![\"\"](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/06\/Screenshot-2026-06-29-at-11.58.35-AM.png\")
Camera trap image puma of a Jasper Ridge in 2018. Image courtesy of Trevor Hebert.<\/p>\n
The researchers used three lines of evidence to trace the changes in the food web. A statistical method helped establish that mountain lions were likely driving the changes, not other factors such as human activity or drought.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/06\/Screenshot-2026-06-29-at-11.58.50-AM.png\")
Coyotes in Jasper Ridge. Photo courtesy of Trevor Hebert.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us-ca\/wp-content\/uploads\/2026\/06\/92a8467a68ba6484f5372dc6c0c8580efd7d81cc823c1a1f46c9977026eb411e.png\")
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