What are those white circles?

If you are a regular visitor to either the Arroyo Pescadero loop trail or the Arroyo San Miguel trail, you’ve probably seen numerous white circles along these trails from time to time. Accompanying these circles are orange signs reading “Please Stay Away From White Circle, Scientific Study In Progress”. But what are these circles, and why stay away from them?

These white circles are track stations which are part of a Habitat Authority wildlife study, established to attract resident wildlife to determine the frequency and diversity of animals in the area. The white powder consists of calcium carbonate (a natural substance that is the main component of limestone), and is the same substance used to create the white lines on baseball and other sports fields. The rock in the center of each circle has a small amount of a scent lure designed to attract animals, particularly carnivores. So, when an animal walks near the track station and smells the scent lure, it walks over the white powder to get a closer whiff of the rock, leaving its footprints in the powder. This is a method used commonly by wildlife biologists, and has been used in the past to study wildlife throughout the Puente-Chino Hills.

Wildlife tracks we have seen over the past five months of the study include coyote, bobcat (in photo at right), striped and spotted skunk, mule deer, ground squirrel, raccoon, cottontail rabbit, and various birds and small rodents. We have also seen many domestic dog tracks, and a few human footprints, indicating that some people either do not read the signs or do not have their dogs on leash. Dog and human tracks may obscure tracks that were left previously by other wildlife, affecting the data and study results.

So, if you see the white circles along the trail, feel free to look and see what kinds of wildlife may have left their tracks, but please try not to leave tracks of your own (or your dog’s). Thank you!