Chorus Frog Eggs

During the volunteer walk this week we stopped for a moment by the pond to search for amphibian eggs. Smallmouth Salamanders lay their eggs as early as February, if there is an early thaw - this year spring came rather late, so they didn't get to the ponds until the first few weeks of March. Western Chorus Frogs and Spring Peepers are early breeders as well - we've been hearing the comb-like trilling of the Chorus Frogs for several weeks now, and the Spring Peepers call mostly during the evening.



Tom N. took a photo of the Chorus Frog Eggs we found attached to a stick in the pond - thanks Tom! Amphibian and reptile eggs in Indiana are protected. It is illegal to remove them from their pond or nest, although after checking with IDNR we were told it was ok to look at them briefly, for educational purposes, as we are doing here.


Smallmouth Salamander Eggs would be similar, but not quite so many and a bit larger. The Chorus Frog eggs will hatch within a few days to a few weeks, depending on the temperatures (with 80 degree days predicted, the eggs will probably develop quickly!). The tiny tadpoles will spend about two months in the pond, feeding on pond scum and algae, before going through metamorphosis and leaving the pond as tiny froglets about the size of your thumbnail. The froglets and adult frogs will spend the rest of year living in the forest, rarely seen by humans, will hibernate under the leaves and in underground burrows made by other animals, to emerge again in the spring and head to the pond to start the cycle all over again!

Spring Peepers

First frog program of the year last night; I was afraid it was going to be too chilly for much frog activity, but we were pleasantly surprised to find the Reflecting Pond absolutely rockin' with Spring Peepers (Pseudacris crucifer) in full chorus. These tiny little frogs are no bigger than your thumb, and can be identified by the vaguely cross-like marking on their backs, which is where the scientific name "crucifer" comes from. They may be tiny, but these little frogs pack some mighty vocal power. A few minutes spent in the middle of an army of chorus frogs and your ears actually ring. ("Army" is the term for a group of frogs, like "flock" is to birds). Only the males call, trying to attract a female. Calling is the most energy expensive activity a frog can do, so the females know that males able to call long and loud are likely to be healthy and good potential fathers for their eggs, genetically speaking, anyway. Once the eggs are laid, both male and female Spring Peepers head back to the forest, and the tadpoles grow up with no parental care needed.
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Here's a video clip of a male Spring Peeper calling, with another nearby, probably a female. The male really puts his whole body into the effort of calling - hopefully the female peeper was impressed!


And another short clip of a peeper calling - this one looked like he waved at me!

Peepers were the only frog we heard calling, but I did spot one very sleepy Bullfrog (Rana catesbeiana) poking her head up. Spring Peepers spend the winter in the forest, burrowed underground. They actually have an anti-freeze-like substance in their bodies that prevents them from suffering damage from sub-freezing temperatures. Bullfrogs, on the other hand, spend the winter under the ice of the pond, hibernating in the leaves and muck at the bottom. Because of the cold temperatures their energy needs are very low, and they can take in enough oxygen through their skin to sustain them.

I could tell this Bullfrog was a girl because her tympanum, or ear, the little circle just beneath her eye, is smaller than the eye. On a male Bullfrog the tympanum is larger than the eye. This doesn't work for Spring Peepers, but you can still tell the males apart by the yellowish or dark brown deflated vocal sac on their throats, while females have white throats.

Chorus Frogs

Spring is here! Maybe not officially, but don't tell the frogs. Temperatures were in the near 70's on Sunday, and the chorus frogs (Pseudacris triseriata) were singing full tilt in the wet areas around the ice skating ponds. It's quite amazing - you can be surrounded by hundreds of frogs singing until your ears ring, and not see a single one! It took me almost 20 minutes of waiting before the frogs closest to me came back out and I could finally locate one. They usually call from the base of a clump of reeds or grasses:


Chorus frogs sing in these ponds in the daytime, but at night the spring peepers take over. By mid-April the chorus frogs all head back to the forest, and we won't see or hear them again until next year, although if you pay VERY close attention, you might notice tiny chorus froglets, no bigger than your pinky nail, leaving the pond in May and June. If you have good speakers on your computer you might want to turn them down - these are tiny little frogs, but they're very LOUD!





The purpose of all of this noise is for male frogs to entice female frogs to choose them for breeding. Singing uses incredible amounts of energy for the male frog, and those that can sing loud and long are likely to be the most fit and healthy mates. The male frog clasps the female in "amplexus" and fertilizes the eggs as she lays them:


Freshly laid chorus frog eggs:

After being in the water for awhile, the clear egg jelly surrounding each egg expands, and the eggs orient themselves dark side up, making them hard to spot against the dark bottom of the pond: