Ask the Naturalist: Where Are the Chorus Frog Babies?

by on October 10, 2013

 

 

Q:  I collect rainwater to use on my garden and I’ve found Pacific chorus frogs in the black garbage can that collects the rainwater, but I’ve never seen eggs or tadpoles in there. I wonder why not; would they be too small to see? [Marian, San Jose]

A: And I always thought they were called treefrogs! Actually, things got confusing in 2006 when scientists split the Pacific treefrog into three separate species. The scientific name for our local species was changed to Pseudacris sierra (though there is still scientific debate about that pending more DNA research) and there are now two accepted common names for the locals: Pacific chorus frog (the newer name) or treefrog. I still call them “treefrogs,” even though they are more likely to be found low in the grass or on the ground close to water. They do have the ability to climb anything, including trees and grasses: An extra joint in the toes gives them great dexterity and the ability to adhere to slick surfaces.

Whatever we call them, these frogs are the most abundant amphibian in the American West, found not only in your rainwater can (and good for you!) but in roadside ditches, farm ponds, etc. They range from British Columbia south to Baja and east all the way to Montana and from sea level up to 10,000 feet.

The adults come in brown or green and every shade betwixt and have the phenomenal ability to change between those colors over a period of time. They use special pigment-containing cells on the surface of the skin called chromatophores to achieve this remarkable feat. But regardless of its color phase, each frog has a dark stripe running from the shoulder through the eye to the tip of the nose, which helps even the novice amphibiophile identify the critter. They are also the smallest of our native frogs, at one to two inches from stem to stern.

They breed during our rainy season, the activity peaking in February and March. Most mating takes place at night, when the loud, rapidly repeated kreckek is the males calling, “I’m a male, I’m a male! Choose me! Choose me! I want to have amplexus with you.” Amplexus, as you might have deduced, is the proper term for amphibian sex.

Females choose a male based on his singing ability and size (yes, they prefer bigger males). When the male grasps the female from behind it stimulates her to deposit eggs on submerged vegetation. The male releases sperm and inseminates the eggs externally. The eggs, each about a quarter-inch across, attach to vegetation in bunches of half a dozen to 80 eggs.

And therein might lie the problem: There may be no suitable place to lay those eggs in your garbage can. Hence the lack of tadpoles (which would definitely be large enough for you to see) and new froglets. Next February put a leafy branch in the can and watch for eggs and tadpoles. Let us know how it goes.

 

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