After five consecutive years of habitat restoration, extensive monitoring, and surveying efforts in freshwater wetlands on both sides of the U.S.-Mexico border, the team has seen a steady uptick in the California state amphibian's presence and egg-laying. This time last year, the team had recorded 181 egg masses. So far this year? They've found 23. The drastic change in numbers begs the question: what changed? 

Many factors can affect differences in egg-laying from year to year. Temperature, food availability, predation, and disease to name a few. The most notable difference though, is the meager 0.35 inches of rain we've received this rainy season thus far. When compared to the five inches of rain we'd received this time last year, the 93% decline in rainfall seems bleak. 

Drought years unambiguously bring higher mortality in plants and wildlife, including increased risk to climate catastrophes like wildfires. For the California red-legged frog, a steady influx of freshwater is a necessity that long-lasting droughts could put at risk. 

While the decline in egg masses raises eyebrows for the team, it doesn't necessarily indicate the population is in trouble. Any wild animal population experiences fluctuations—sometimes highs, sometimes lows. The lowest numbers give us an idea of the minimum population size required for a species to survive. The problem is scientists don't know what that threshold is for the frog populations they’re studying—yet.  

When the project first began in 2020, California red-legged frogs had been declared extinct in San Diego County. Slowly, reintroduction efforts from ponds in Baja California to ponds in San Diego and Riverside counties have repopulated sites in Southern California where the frog was previously extirpated. Today, thanks to the efforts of The Nat's herpetology team, plus the many biologists at U.S. Geological Survey, The Nature Conservancy, California Department of Fish and Wildlife, U.S. Fish and Wildlife Service, and Fauna del Noroeste, the frogs are colonizing new ponds on their own.  

Although years of high egg production prove exciting, years with low egg production like this one give scientists key information about the amphibian's population dynamics, filling knowledge gaps that are invaluable for the threatened frogs’ survival and conservation.  

To learn more about the California red-legged frog and the herpetology team’s conservation efforts, visit https://www.sdnhm.org/science/herpetology/projects/california-red-legged-frog/.