Almost all of the turtles living in a southern California lake died following a large fire and years of drought, according to a new U.S. Geological Survey report published in the journal Knowledge and Management of Aquatic Ecosystems.
This study is the first to examine the interaction of fire and drought on the survival, behavior and health of a semi-aquatic turtle population. Given the likelihood of increasing drought frequency in California’s future, conservation of the southwestern pond turtle (Actinemys pallida), along with other sensitive aquatic organisms, will become an even greater challenge. The southwestern pond turtle is a California Species of Special Concern.
Scientists from the USGS Southwest Biological Science Center documented the significant mortality event in Elizabeth Lake, located in the Angeles National Forest of northern L.A. County. In 2013, a large fire occurred around the lake during prolonged drought conditions. USGS scientists began collecting water-quality data and assessing the health of the turtles in 2014. Findings showed the fire put large amounts of ash into the lake, contributing to the deterioration of water quality already caused by the drought. Many turtles were severely emaciated and coated with a pale mineralized layer on their shells and skin. The lake dried up in September 2015 and most of the turtles died off. USGS scientists worked with the California Department of Fish and Wildlife to place about 30 turtles under veterinary care at the Turtle Conservancy in nearby Ojai, California.
“Fire and drought are naturally occurring disturbances that have profound impacts on ecosystems and ecological processes,” said Jeff Lovich, a USGS scientist and lead author of the study. “Understanding how wildlife responds to these stressors will help resource managers make informed decisions in the future.”
Findings showed that all the fish died, the food web collapsed and most turtles had nothing left to eat. Deceased turtles were sent to the USGS National Wildlife Health Center for analysis, and were confirmed to have died of starvation. Although this semi-aquatic species has the ability to move to upland habitats or nearby water bodies during periods of low water, it is unlikely that many were able to do so because of their extremely poor condition and the severity of the drought conditions throughout the area.
It is possible that the population would have been able to survive the effects of drought or fire alone, but the combination appears to be responsible for the mortality observed.