Factors affecting the permeability of clearcuts to red-legged frogs

Forest harvesting may create movement barriers that prevent forest vertebrates, especially amphibians, from accessing seasonal habitats or dispersing to new home ranges. I radiotracked 120 red-legged frogs (Rana aurora aurora) in 3 experimental sites on Vancouver Island, British Columbia, Canada, to examine the potential barrier effects posed by voting clearcuts. I found that clearcuts <12 years old were significant barriers to movement by red-legged frogs, but the permeability of these clearcuts was highly dependent on weather and to a lesser extent on body mass. Under the maximum observed noon temperature of 34.2 degrees C, the permeability of voting clearcuts dropped to 2.3%. The permeability of young clearcuts equaled 16.7% in the absence of rain, under average temperatures and humidities experienced during the trials. A significant site effect suggested that the barrier effects of clearcuts may be diminished in regenerating stands as young as 11 years old. Red-legged frogs were attracted to 3-m-wide streams but not to those <= 1.5-m wide. The relationships I present should allow estimation of the permeability of clearcuts to other red-legged frog populations in areas with different regional weather patterns or mean frog size.