OXBOW MYSTERY

When a channel cuts through the steep bank in a meander loop there’s a distinctive landform produced called an “oxbow”. This blog has a number of posts describing our oxbow because it’s a cool complex of unique small environments in the Creek pasture. These are each different ecologic habitats that support different populations of plants and animals. You can use the “Search” box to find some of the other posts about oxbows, but this post is about a specific critter in particular environmental setting.

This air photo has the several small constituent subdivisions labeled on the overall oxbow. The upstream and downstream plugs separate the oxbow from the main channel and the tie channel further separates the channel from the pond. The pond and the wetland are the main components. If the water level is high enough, they both get water from the main channel. However, when water levels are low the pond is sustained by groundwater flow from a buried gravel aquifer exposed in the steep north bank. The wetland, on the other hand, has completely dried up at times when low water levels are maintained. The oxbow mystery is located in the pond-wetland transition.

The pond-wetland transition seems to be the home of a colony of rare little frogs called cricket frogs. Like Topeka Shiners, they are a native species found in prairie streams. They have a distinctive call that sounds like two rocks striking together. Here’s a link to the post that describes this little guy and his voice: https://lonetreefarm.blog/2019/07/03/frog-calling/

These frogs are usually first heard in the late spring. In 2017 it was June 11; in 2018 it was May 24; in 2019 it was July 1; and this year it was June 12. But, this year I noticed a peculiar pattern. The only place that I heard these distinctive calls was in the pond-wetland transition. I checked the other main parts of the oxbow another 3 or 4 times after June 12, but the pond-wetland transition was the only place where the cricket frogs called.

Why do these little guys like that particular part of the oxbow? The plants along the bank close to the water seem to be basically the same as in other subdivisions. Is there some water quality aspect related to the ground water that flows into the pond? Are there particular food sources like distinctive insects in this transition zone? Do other colonies of cricket frogs have a similar preference for a distinctive environment similar to this transition zone?

It’s a “puzzlement”.