Significance of burrow-opening diameter as a flood-prevention mechanism for air-filled burrows of small intertidal arthropods

Small air-breathing terrestrial arthropods (e.g. beetles, ants, crabs) living within the intertidal zone of mud and sand flats construct burrows with a narrow opening to the substrate surface. Despite frequently remaining open, these burrows are not flooded by the incoming tide. We examine, from a theoretical standpoint, the rôle of burrow-opening diameter in preventing burrow flooding. We determine a critical burrow diameter of 3 mm above which burrows are likely to flood unless the entrance is plugged by the burrow's inhabitant(s) prior to tidal inundation. We examine water penetration via the burrow entrance and seepage through the burrow walls. A practical mathematical solution is provided which can be used to examine the extent to which water may penetrate a given animal burrow in the field.