August 16, 2014
Posted by: PU - Park Ranger (Hodgdon Meadow)
How does a Sierra tree frog (
Pseudacris sierra) keep from drying out at mid-summer Hetch Hetchy when temperatures can reach the triple digits and humidity can dip below 20%? Go deep. Deep into the granite that is. The bottom of deep cracks can serve as minute reservoirs where temperatures are cool and humidity is high. Standing pools are unnecessary. A consistent drip is all that is required for frogs to absorb water through their highly permeable skin. Frogs retreat into these refugia and wait out the summer to emerge in the late winter and early spring to feed and breed once again on the surface when temperatures drop and humidity rises. Permeable skin is an obvious adaptation that allows amphibians to passively absorb moisture from their environment. This same adaptation has perhaps rendered all amphibians more vulnerable to absorbing human introduced toxins in the water and the atmosphere than other animals.
Nature Scene, Hetch Hetchy
