American Bullfrog — Unwanted Invader

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I visited Sweetwater Wetlands today for the first time in weeks.  Not much was going on there.  The ducks have all but vanished and a lot of the migratory species that pass through the wetlands in spring had moved on to their summer residences.  One could say that the place was very quiet but for the persistent calling of bullfrogs.

The wetlands are overrun with American Bullfrogs.  There are at least several hundred residing there and that may be a big understatement.  Their mating calls fill the air this time of year.  They sound exactly like what someone would sound like if he or she attempted to play the low notes on the bagpipes for the first time in his or her life.  The frogs’ calls are loud, in a lower register, and entirely unmelodic.

I spotted several bullfrogs sitting at the margins of ponds.

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These frogs are big — some of them 8 or 9 inches in length and weighing well upwards of a pound — and their appearance is striking. Their brilliant chartreuse-green faces contrast sharply with their darker colored bodies.

American Bullfrogs are an invasive species in southern Arizona.  No one really knows how they got here, but they are now everywhere where there is standing water.  They are generally considered to be a nuisance.  They’ve crowded out other species of amphibians, and sometimes, fish, and in some places diverse amphibian cultures have been replaced by a bullfrog monoculture.

They’re extremely successful for a number of reasons.  First, because they are physically so tough.  A bullfrog can travel quite a distance across a dry desert in search of living quarters, and so, they’ve been able to travel from stream to stream, to irrigation canals, and to ponds.  They are much bigger and far more aggressive than most other amphibians.  They reproduce at a phenomenal rate and their offspring attain maturity very quickly.  They have voracious appetites.  A bullfrog has a gigantic mouth and it will use that mouth to grab insects, fish, other amphibians, including younger bullfrogs, an occasional mouse or other small mammal, and even unwary birds.

I had decidedly mixed feelings about photographing this frog.  On the one hand, it’s quite handsome and a definite part of our environment now.  On the other hand, there are a lot of species that are no longer here because the bullfrog is here.

Image made with a Canon 5Diii, 400 DO, aperture priority setting, ISO 2000, f6.3 @ 1/500.  I stabilized the camera by bracing it against a metal railing.


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