Oxbow Farm & Conservation Center

This is a companion project to a 2016 CREOi award.

Globally, amphibians are threatened by fungal diseases, climate change, and habitat loss and fragmentation. In urbanizing areas like western Washington State, road corridors and increasing traffic may contribute to habitat fragmentation, blocking amphibian migration paths between spring breeding ponds and the upland forests that provide overwintering habitat. Oxbow staff and volunteers conducted 3 nocturnal road surveys along 60 miles of floodplain-marginal roads to assess traffic mortality and identify hotspots of amphibian road crossing. Eleven floodplain ponds and wetlands were surveyed in the Snoqualmie River valley across a gradient of traffic fragmentation to characterize amphibian species presence and abundance and to assess the impact of roads that separate breeding and winter habitats. We observed 2,745 amphibians on roadways (98% tree frogs, 96% dead) over the course of 3 nocturnal surveys, and we identified 4 hotspot road sections where amphibian crossing and mortality was significantly higher than in other areas. Four hundred thirty two (432) egg masses were observed during surveys of study ponds, comprising 287 northwestern salamander masses, 100 Pacific tree frog egg masses, 28 long-toed salamander masses, and 17 northern red-legged frog masses. No significant correlation was found between traffic level on adjacent roads and egg mass numbers, but northwestern salamander egg mass abundance was correlated with emergent wetland area present at a site. Low northern red-legged frog abundances in this study indicate that there may be insufficient forest cover near ponds to support robust populations. The study raises the possibility that populations of some amphibian species may be adapted to avoid roadways and may instead rely on adjacent floodplain habitats for overwintering, despite the stressors present in these habitats. Oxbow staff are actively incorporating information about local amphibians into classroom lessons to increase public understanding of amphibian conservation issues and reaching out to partners and community groups to share our findings. ($15,000)