Green Frogs and Bullfrogs

     I remember with pleasure occasionally taking a canoe out on an eight acre pond on summer evenings in southeastern Pennsylvania.  I stayed on that human-made impoundment until dark and saw several entertaining little brown bats flickering and swooping over the water after flying insects to eat and a silent, fantasy world of innumerable, flashing fireflies in the woods surrounding the pond.  And I heard many unseen green frogs and bullfrogs twanging and bellowing respectively and loudly along the shores of the impoundment.  The darkness over the water, bats, fireflies and frogs all combined to make enchanting evenings in a canoe on the pond.
     One can hear the gutteral belching of green frogs and the low moaning of bullfrogs from most any pond, marsh, roadside ditch, sluggish waterway and any other permanent water body, day and night, through June and July in this area.  Some even live on the edges of backyard goldfish ponds, where they were introduced as tadpoles or wandered in themselves on rainy or dewy summer nights as adult frogs or froglets.  But wherever they are, the boisterous croaking of green frogs and bullfrogs helps make summer nights more mysterious and intriguing.  
     Those froggy calls are from males coaxing females of their respective kinds into water to spawn.  Each female of both kinds spawns thousands of eggs in several scattered clusters attached to submerged vegetation.  The eggs and resulting tadpoles receive no protection or guidance from their parents, ever.  The tads eat algae and other aquatic plants and decaying animal bodies in the water.  They take almost two years to transform from polliwogs to froglets.
     Green frogs and bullfrogs are both in the Rana genus, and are closely related to each other.  Therefore, they have characteristics in common.  Both species are adaptable and quite common in southeastern Pennsylvania, as they are across much of the eastern United States.  Both types are mostly green and brown, with darker markings on their smooth, moist skins.  Both are predatory, feeding on invertebrates and any other critters they can stuff into their large mouths.  Adult males of both species have larger ear drums than do females of their kinds.  Adult, breeding males of both types have yellow throats.  And, as with all frogs, these species have their tongues attached to the front of their mouths so they can flip their mucus-covered tongues out, snare intended victims with their sticky tongues, and flip that prey back into their caverns to swallow whole.
     Green frogs and bullfrogs do have a few differences between them, however.  They have different calls to attract females for spawning.  Bull frogs are bigger. And green frogs have a ridge down each side of their backs, which bullfrogs don't have.     
     As with all frog species and their tadpoles, green frogs and bullfrogs, and their fish-like young, have many predators.  Larger fish, turtles, water snakes, kingfishers and herons are some of the wildlife that prey on polliwogs.  And mink, raccoons, herons, barred owls, red-shouldered hawks and other critters catch and ingest adult frogs.  With such heavy losses, no wonder that producing lots of eggs per female helps keep frog populations going.
     When out near water in summer, listen for the burping and groaning of these two kinds of common frogs.  They help make summer more interesting.