Signs of Spring

by Adams and Anders
Upland Chorus Frogs (Pseudacris feriarum) have a variation of color palettes, but commonly brown to grey with a pinkish cast. Adults range from 0.75 inches to 1.5 inches, with females usually being slightly larger than males. They are often hard to track to a precise location because the pitch of the call echoes in their common locations. They are often found in moist woodlands, river bottom swamps, ponds, bogs, and marshes. They are most active immediately after hard rains and at night. This is most common during the breeding season, between November and March (depending on temperature and rainfall), and much more difficult in the non-breeding season. The females lay approximately a thousand eggs at a time, attached to vegetation, during this season.
We conducted an experiment on the calls of the Upland Chorus Frogs stemming mainly from our own curiosity. We measured how close a potential predator (us) could get to the frogs before they stopped calling and when they began calling after the perceived threat moved on. We found that a small water hole, which is actually a water runoff site, gave us our best chance to collect some data. During the first trial, we were able to get within 20’7” before frogs stopped calling. They resumed their chirping 8.6s after we moved on. The second trial had the frogs ceasing at 16 feet, taking 5 min. 10s to resume. The third test had the frogs stopping at 15’11” and starting back at 4 min. 55s. The fourth and final test resulted in the frogs stopping at 21’ and resuming after 9 min. 8.6s. The frogs seemed to sense the danger the more times we enacted the test.
There is no known research that has measured how close potential predators could get before these frogs stop calling. There did not seem to be a definite pattern as to when they stopped calling. However, the time it took them to resume after we had walked by did increase. Were they just annoyed that we kept “bothering” them or did they really think we were a danger. We did try this study at another marshy location that is considerably larger and could not get the frogs to stop calling. Is this because of the size of the frog population in that area?  Is there strength in numbers? Could the larger groups be less afraid of potential predators? How can simple little frogs sense when danger is near? These questions may drive us to perform more experiments in the near future.
The following shows some additional information on these frogs:

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