Ghost crab burrows simulation shows differential across-shore persistence

Abstract

Ghost-crab abundance is often used as an indicator of sandy beach environmental quality. Most studies use an indirect approach, assuming a direct relationship between the number of burrows and individuals. We here hypothesized that burrows could remain open for different periods of time according to the beach strata. We performed a field manipulation to simulate burrows, with persistence of each one individually assessed over a month. Results succeeded in demonstrating a significant differential persistence of burrows among beach compartments (backshore, frontal dune, and coastal vegetation, i.e., in a landward oriented sequence), which can affect abundance estimates and are thus prone to overestimating larger size classes, which inhabit the landward limit of the species’ range of occurrence. We recommend that this information is taken into consideration in population studies, and encourage the development of similar studies over broader spatial and temporal scales.

Burrowing behavior and burrowing energetics of a bioindicator under human disturbance

“…For the burrow fidelity, we sampled the newly created burrows over a 1‐week period in three replicate rectangular quadrats (10 × 5 m) situated on the seaward side of the dune vegetation at each site. We established our quadrats near the dune vegetation because the persistence of ghost crab burrows is directly affected by the tides (Evans, Cram, Eaton, Torrance, & Wood, ) and height on the beach (Campagnoli, Pombo, & Turra, ). We first measured burrow size as the largest distance across the burrow openings, which is positively related to crab size ( r 2 = 0.98, Wolcott, ; Silva & Calado, ; de Oliveira, Souza, & Soares‐Gomes, ; Souza, Oliveira, Tardem, & Soares‐Gomes, ).…”

“…We established our quadrats near the dune vegetation because the persistence of ghost crab burrows is directly affected by the tides (Evans, Cram, Eaton, Torrance, & Wood, 1976) and height on the beach (Campagnoli, Pombo, & Turra, 2018). We first measured burrow size as the largest distance across the burrow openings, which is positively related to crab size (r 2 = 0.98, Wolcott, 1978;Silva & Calado, 2013;de Oliveira, Souza, & Soares-Gomes, 2016;Souza, Oliveira, Tardem, & Soares-Gomes, 2017).…”