Burrowing of the fiddler crab Uca tangeri in the Ria Formosa in Portugal and its influence on sediment structure

Abstract

Individuals use the same burrow for c1 wk, then occupy another or dig a new one. Overall a burrow is inhabited for c3 mo by several individuals before it is abandoned. Vacated burrows decay within 2-3 wk. Burrow density was highest in spring and early summer with 17 burrows m-2, then decreased. Deepest burrows (up to 90 cm long) were found in winter, the shallowest (up to 40 cm long) in summer. Volume of the sediment moved by U. tangeri varied monthly between 3000-6000 cm3 per m2 of mudflat. Water is only found in the lower third of the burrow. Burrow water contains less oxygen and more nitrate than the surrounding water. -from Author