Date of Award


Document Type

Restricted Thesis

Terms of Use

© 2006 Micah J. Horwith. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

Rachel Merz


The mole crab Emerita talpoida and the coquina clam Donax variabilis inhabit the swash zone of the American Atlantic coast, riding waves to follow the advance and retreat of the tide. Uneven distribution of these animals along Cape Henlopen, DE, led to a hypothesis that any factor that slows burrowing will prove limiting to crab or clam settlement in the limited window of low flow that accompanies the high point of a wave. In the laboratory, crabs and clams burrowed in sediments of varied coarseness and sortedness, and crabs also burrowed in the presence and absence of clams. Small crabs burrowed significantly more slowly in coarser sands, while sortedness did not affect crab burrowing. Clams burrowed significantly more slowly in coarse/sorted sand. Crabs burrowed significantly more slowly in the presence of clams. In the field, there was no significant correlation between sediment characteristics and crab number, while there was a significant negative correlation between sortedness and clam number. Numbers of crabs and clams exhibited no significant correlation. Differences between these species in absolute burrowing speeds may suggest that factors that slow burrowing prove limiting to slow-burrowing clams, but not to rapid-burrowing crabs.