BEACH STRUCTURES PRODUCED BY CRAB PELLETS

ABSTRACT It has been observed that seashore crabs produce various designs by the ejected faecal pellets. Study of such structures shows a clear association of them with different parts of the beach. Mossy structures are found only in the upper beach part, i.e., along the high‐water line, whereas concentric‐radiating and asteroid types are encountered in the middle beach area. In regions above mean high‐tide line burrow openings are surrounded by loose sediments and are devoid of any patterns. In the lower beach zone such structures are lacking. If the beach materials are more silty in character, faecal pellets congregate and stand out as knobby surfaces. Closer examination of such structures, if preserved in ancient sediments, may not only help in delineating the ancient shoreline positions but also may help in demarcating littoral micro‐environments.