Are these creatures in the riverfront sand?

Asked October 29, 2013, 2:13 PM EDT

Last Saturday, I spotted interesting patterns of nicely curved grooves in the sand in Sellwood Riverfront Park on the east shore of the Willamette River. I noticed what I thought were small dark pebbles at the end of many of the trails, and assumed that the pushing of river water from boat wakes and water level changes, etc, was responsible for creating the exotic grooves. I discovered upon viewing the photos at full resolution that the "pebbles" appear to have a biological structure. The objects I describe are approximately .5 to 1.0 inches in length.
All of these paths I observed were scrawled all over an 8-to-12-foot wide swath of saturated sand at the water's edge on the gently sloped riverbank. They were very numerous along several hundred feet of the river's path.

Are these some type of creature moving on their own, or perhaps just some kind of seedpod that the water moved around? It seems more likely to me now that they were moving on their own when I look at the characteristics of the paths, but I'm certainly no expert. I noticed no movement at the time but did not look for it as I thought they were pebbles. I have attached a crop from one of my pictures showing the objects and their paths. Please let me know if you are able to identify them. Thanks!

Multnomah County Oregon invertebrates snails rivers aquatic ecosystems

1 Response

Hi, what a great question! Yes, they are creatures. They are some kind of a snail, although I can't give you the exact species that you've observed. Many times, people don't realize how mobile snails and clams can be. They leave a great trail in the sand showing where they've been.

Hope this helps!

Rebecca