You are here:
AMPHIBIAN OCCURRENCE AND AQUATIC INVADERS IN A CHANGING LANDSCAPE: IMPLICATIONS FOR WETLAND MITIGATION IN THE WILLAMETTE VALLEY, OREGON, USA
Citation:
PEARL, C., M. ADAMS, N. LEUTHOLD, AND B. BURY. AMPHIBIAN OCCURRENCE AND AQUATIC INVADERS IN A CHANGING LANDSCAPE: IMPLICATIONS FOR WETLAND MITIGATION IN THE WILLAMETTE VALLEY, OREGON, USA. WETLANDS. The Society of Wetland Scientists, McLean, VA, 25(1):76-88, (2005).
Description:
Despite concern about the conservation status of amphibians in western North America, few field studies have documented occurrence patterns of amphibians relative to potential stressors. We surveyed wetland fauna in Oregon Willamette Valley and used an information theoretic approach (AIC) to rank the associations between native amphibian breeding occurrence and wetland characteristics, non-native aquatic predators, and landscape characteristics in a mixed urban-agricultural landscape. Best predictors varied among the five native amphibians and were generally consistent with life history differences. Pacific tree frog (Pseudacis regilla) and long-toed salamanders (Ambystoma macrodactylum) occurrence was best predicted by the absence of non-native fish. Northern red-legged frog (Rana a. aurora) and northwestern salamanders (Ambystoma gracile) were most strongly related to wetland vegetative characteristics. The occurrence of rough-skinned newts (Tarica granulose), a migratory species that makes extensive use of terrestrial habitats, was best predicted by greater forest cover within 1 km. The absence if non-native fish was not strongly related to native fish presence. We found little evidence supporting negative effects of the presence of breeding populations of bullfrog (Rana catesbeiana) on any native species. Only the two Ambystoma salamanders (which usually have a multi-year larval stage) were associated with permanent waters, while long-toed salamanders were associated with temporary wetlands. Although all the species made some use of upland habitats, only one (rough-skinned newt) was strongly associated with surrounding landscape conditions. Instead, our analysis suggests that within-wetland characteristics best predict amphibian occurrence in this region. We recommend that wetland preservation an mitigation efforts concentrate on sites lacking non-native fish for the conservation of native amphibians in the Willamette Valley and other western lowlands.