HURRICANE WASHOVER SANDS PROVIDE A SUITABLE SUBSTRATE FOR REGISTERING RARE TRACKWAYS IN BAHAMIAN MANGROVES

Coastal mangroves serve as a habitat for a diverse suite of organisms that interact with a substrate in a variety of ways. However, highly heterogeneous media common for supratidal biotopes make preservation of surface traces difficult. In carbonate settings, a combination of actively growing vegetation, phytodetritus, and incipient lithification of fine-grained surface sediments combine to greatly reduce or preclude preservation of vertebrate and invertebrate traces. This study reports several trackways produced by birds and crustaceans on a sandy washover deposited by Hurricane Joaquin (October 2015) along the shore of North Pigeon Creek (San Salvador Island, the Bahamas). Field measurements, photography, and casting were used to record spatial relationships of the ichnites during surveys conducted 3 and 15 months following this intense storm. Avian tracks (total length: 6 cm) show three forward-directed toes lacking webbing, with the rear-pointing extension attributed to a hallux. They were likely made by a small ardeid, one of several species of heron common along this part of the island. On the same surface, trackways characterized by a series of multiple 3-cm-long cone-shaped depressions extend for >1 m across the open sand and terminate in vegetated areas along the leading edge of the washover. The width (6-14 cm) and partial impressions of an abdomen identify their tracemaker as a blue land crab (Cardisoma guanhumi), a common decapod that inhabits multiple burrows in the surrounding supratidal lowlands. A sharp bend in one of the trackways is associated with avian footprints and may record predator avoidance. These findings indicate that in muddy substrates complicated by cementation and dense vegetation, introduction of sand by storms, aeolian activity, or for improvement of access paths, may offer unique opportunities to register and ultimately preserve a rich ichnological record.