From: Ann Mansker
Subject: Re: Critter of the Week: Rana sylvatica
Date: 16 Nov 1998 07:25:53 GMT
Newsgroups: ucd.life
The Wood Frog ( http://ednet.ns.ca/educ/museum/mnh/nature/frogs/wood.htm ),
as its name suggests, is a terrestrial frog living in woodland and forest
habitats. The wood frog is found from northern Georgia up through the
northeastern United States and all the way across Canada into Alaska. It is
the only frog found north of the Arctic Circle.
A rather handsome frog, this species exhibits a number of color morphs,
usually browns, tans and rust, but also grey and green. In all cases, it
has a dark mask across the eyes, leading to the other common name of Robber
Frog.
In winter the Wood Frog burrows under forest floor leaf litter and prepares
to suspend life until spring. The suspension is quite literal -- as the
temperature falls, the frog cools also. Eventually ice crystals forming on
the skin triggers the frog's liver to convert glycogen to glucose, which
floods the creature's cells. This serves to protect the cells as the water
in the frog's body begins to freeze. The eyes and brain become solid, the
heart and lungs stop, and up to 65% of the water in the frog's body turns to
ice. In this state, the animal waits out winter, insulated by the material
covering it, augmented by a blanket of snow. Alaskan frogs have been
measured as surviving temperatures of 10 degrees Farenheit, though their
southern conspecifics may not be as hardy.
When Spring comes, the frog thaws very quickly and immediately seeks water
and mates. The male's call ( http://imc.lisd.k12.mi.us/frog/wood.html ) is
sometimes mistaken for a duck's. Wood frogs congregate in temporary wet
areas, typically vernal pools, only to lay eggs. After that, they disperse
into the surrounding forest and spend the rest of the year foraging for the
typical frog diet of whatever small invertebrates they can fit in their
mouths. The young develop very rapidly; if the temperature is warm enough,
they can go from egg to froglet in about 60 days.