UWEC CERCA 2026

Widespread human impacts – from climate change to unprecedented rates of human visits in once relatively untouched wilderness areas – contribute to rapidly changing selective pressures on wildlife. Long-term studies on marked individuals can offer insights into population and community dynamics over time. The current research aims to reveal the demographic and behavioral patterns of California ground squirrels (Otospermophilus beecheyi) before and after a boom year of California voles (Microtus californicus). Our field study in California has live-trapped, marked, and released individual ground squirrels since 2013 at two study sites. We also directly observed behavioral interactions among squirrels, recorded predator sightings at landmarks, and conducted behavioral assays to assess fear responses to humans. In Summer 2024, we documented the emergence of widespread hunting and consumption of voles by ground squirrels in our two study populations. By Summer 2025, the ground squirrel population crashed, whereas predator numbers soared. We report on these patterns as well as increased fearfulness by squirrels and increased predator sightings, which exceeded numbers documented in previous years. Our findings offer insights into how periods of prosperity (e.g., boom years) and catastrophic turnover events (e.g., demographic crashes) shape wildlife populations that generate ripple effects within ecological communities.