Friday, March 18, 2011

Wood Frog Activity Peaks

Amazingly, wood frog (Rana sylvatica) activity in vernal pools is nearly finished in southeastern Belmont County for this season.  Breeding populations have vanished almost as quickly as they appeared a little over a week ago.  Wood frogs are notorious for arriving poolside in large numbers on short notice, then disappearing shortly thereafter into upland forests to forage for the remainder of the growing season.  With such a short window of pool time, witnessing a peaking chorus requires observation of key environmental conditions and a little experience.  Next up in local vernal pools is the more familiar spring peeper (Psuedacris crucifer) which was heard chorusing throughout the southern end of the county last night.

A chorusing male wood frog in a vernal pool.  Males will float
in a section of pool as they call females.  This pool contained
five chorusing males but the presence of several egg masses
suggests peak breeding occurred last weekend.  Vocalizations
sound like ducks and have little carrying power.  Note the
"robber's mask" passing through the eye and paired dorso-
lateral folds on the back. 

These guys are hard to sneak up on in broad daylight!  Another
male in the same pool.  Note the bars on the hind legs.  This
guy is getting ready to head for cover.

Wood frogs exhibit much variability in color which is not a good
characterisitic for identification.  This is the tan phase which
blends in well with clay soils.  In pools with little vegetative
cover, individuals will try to burrow into the muddy bottom
face-first to escape detection.  Not sure how well this works
to fool snakes and other predators.

More wood frog egg masses.  Amplexed pairs will lay masses
communally which conserves heat thereby accelerating
development.  These guys are in a race against time to complete
metamorphasis into froglets before the pool dries out in early July.
Rate of development is largely dependent on water temperature.

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