Terrestrial movements of juvenile and adult tailed frogs in relation to timber harvest in coastal British Columbia

Abstract

Tailed frog (Ascaphus truei Stejneger) populations are at risk in much of the Pacific Northwest, and recolonization of sites may be slow postlogging. To examine the terrestrial movements of Ascaphus in clearcuts and old growth, we employed pitfall traps and drift-fence arrays installed along streams and 100 m into upland habitat. In the fall, we captured frogs farther from streams in old growth than in clearcuts, and more frogs were captured ≤25 m from streams in clearcuts. Stronger stream affinity in clearcuts was most evident with juvenile frogs, which exhibited more upstream movements than adults. Compared with inland sites where frogs remained close to streams (e.g., 12 m), frogs at our coastal sites were captured at greater distances from streams (≥100 m), having lower stream affinity than frogs at inland sites. Long-distance overland movements appear more likely where forested stands are present. Aggregations of Ascaphus at individual streams may not represent distinct populations and should not be managed as distinct units. Preserving groups of interconnected streams within watersheds instead of individual streams will improve the conservation status of Ascaphus. Population monitoring can ensure conservation measures promote long-term persistence.