Anuran Chorus at Stossel Creek

Pacific Tree Frogs were in full chorus, and a few American Bullfrogs added to the performance. The marsh system along Stossel Creek provides ideal habitat for these species.

The frogs were in full chorus. Swamp stretched across the valley for a hundred yards and for a half-mile along Stossel Creek. A mixture of willows and grasses grew in the wetlands, and then a pond opened downstream from this spot. The loudness and diversity of their songs made me think that hundreds were singing simultaneously. These were Pacific Tree Frogs Pseudacris regilla, and I was trying to absorb that a tiny anuran, less than 2 inches long, could make that much sound.

They also go by the name Pacific Chorus Frog and hearing this choir made me think that chorus frog might be a better name. When one male begins to sing, any nearby male will jump right in and try to outsing the other. Each puffs out its vocal sack as it puts forth the song. This was not an organized chorus with all of them singing together, but rather each male was trying to out-compete the next. If he succeeds, a female may come his way. He needs to sing louder or differently to entice her to pay attention to him. 

In the distance, I noticed the deeper and more resonating call of an American BullfrogLithobates catesbeianus. This introduced species is a severe problem in Washington. The Washington Department of Fish and Wildlife has listed it as an invasive species. Bullfrogs grow to be big. With their legs stretched out, they can be up to ten inches long and are voracious predators, eating anything they can catch. They were natives in Western Pennsylvania, and I searched for them along the shoreline of ponds near my parent’s farm. 

At fifteen minutes into my recording, a lull of ten seconds happened. Perhaps, one male needed a break to catch a snack, and all the rest followed, but I suspect it was more likely that one sensed a possible predator nearby, and they went silent. Eventually, one male frog couldn’t resist and croaked. The rest then started back up. Barred Owls are common in these lowland forests of the Pacific Northwest and will hunt these frogs. 

Tree frogs need to breed, though; these anurans sing even if it exposes them to the risk of being eaten. 

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