Resource selection and movement of the coastal tailed frog in response to forest harvesting

Abstract

The coastal tailed frog (Ascaphus truei) has a biphasic life-history that includes the use of montane streams adjacent to mature old growth forests. This species is at risk from a variety of land-use activities, including forest harvesting, that results in younger and more fragmented terrestrial habitats. Post-metamorphic tailed frogs are cryptic and difficult to capture, making for few studies of the terrestrial life stage of the species. At the northern extent of the species’ range, we investigated the spatial ecology of tailed frogs across riparian and adjacent upland forest in three forest types: mature to old unharvested, streamside forest retention, and clearcut. Post-metamorphic frogs were fitted with Very High Frequency radio transmitters and monitored for an average of 10.75 days (SE 0.89). Females moved further from their origin of capture during the monitoring period (x¯= 68.89 m, SE 16.3) when compared to males (x¯= 36.85 m, SE 7.9). We used Resource Selection Functions to quantify habitat selection of female and male tailed frogs. Monitored frogs were positively associated with habitats containing well-decayed coarse woody debris (≥ 7.5 cm diameter), less ambient light, adjacency to the larval stream, hygric and subhygric microsites, and cool temperatures (11–12 °C). Females were more selective in their choice of habitat than males. Overall, the relationship between distribution and activity of tailed frogs was reflective of the sex of the frog in combination with microsite or broader climatic conditions ameliorated by stand-level habitat conditions. Our data suggest that habitat management for post-metamorphic tailed frogs focus on the retention of both streamside (within 40 m) and upland forest (> 50 m from larval stream), as well as stand-level attributes such as hygric and subhygric microsites, and coarse woody debris with advanced decay.