5) Warren (1990) showed that it is viable to use burrows as estimators of the density of ghost crabs on sandy beaches.
He noted a strong correlation between the number of burrows and the number of Ocypodidae crabs.
Besides, Barros (2001) argued that if density of burrows is not a true estimate of crab abundance, at least it shows that crabs from urban and non-urban beaches display distinct behavior.
The results of this survey may indicate that ghost crabs is showing differences in behavior on urban and non-urban beaches at Rio Grande do Sul state.
Ghost crabs inhabiting urban beaches may not construct open burrows, or may not maintain their burrows, as they do on non-urban beaches. Future surveys must elucidate this point.
6) Studies into the effect of human activities on beach fauna have been neglected, and few are found in the literature (Heath, 1987).
Jaramillo et al. (1996) found no evidence of human impact on the fauna of a sandy beach in Chile, although they did not consider the density of ghost crabs.
Steiner and Leatherman (1981) suggest that the density of ghost crabs on beaches with a frequent human presence was higher than on beaches little visited by humans.
This is probably due to people leaving scraps of food on the beach which the crabs feed on.
However, these results must be analyzed with caution due to minimal spatial replication (Barros, 2001).
In this study, there was not found to be a higher density of burrows on the beach with the greatest human presence. Nevertheless, the combined effect of the presence of humans and cars may contribute to a lower density of ghost crabs, especially at T. beach.
7) The results found in this study are similar to those found by Barros (2001) on Australian beaches.
He discovered that urban beaches had a significantly lower number of O. cordimata burrows than non-urban ones, suggesting that the number of burrows may be a useful and simple indicator for verifying the anthropogenic impact on the fauna of sandy beaches.
8) In one of the few studies into the ghost crab in Rio Grande do Sul, Alberto and Fontoura (1999) observed that they prefer to build their burrows in the large, central area of the beach, although migration may occur in adverse conditions.
This was observed at all three beaches in this study on days when storms occurred.
Distribution of the burrows was restricted to the highest areas of the beach on these days.
Furthermore, at T. on the last day distribution of the burrows went beyond the strip which cars use, reaching a distance
of 3 m from the dunes.
The sea level starting to rise flooded the kiosk area, driving the ghost crabs population to the highest area of the beach. Yet no burrows were found in the strip used by cars.