Does trace density reflect tracemaker density? A test using intertidal gastropods on San Salvador Island, the Bahamas

Abstract Trace densities may be a potential proxy for tracemaker densities, especially in settings where traces but not body fossils preserve well. The relationship between the density of the gastropod Batillaria minima and its trails was examined in a modern muddy intertidal zone of a lagoon on San Salvador Island, the Bahamas. The number of snails found within a quadrat was a moderately positive predictor of the number of trails that crossed the quadrat’s boundaries. This suggests in some modern ecological systems, trace density is a reasonable proxy for tracemaker density. However, in some cases, high densities of snails are found without correspondingly high trail densities, which may be driven by the snails clumping or moving little, perhaps to access shared resources. Observations of tagging individual snails and speed measurements also suggest that B. minima disperses around this type of mudflat habitat a few tens of centimeters a day.