WETLANDS, Vol. 22, No. 3, September 2002, pp. 489498 O 2002, The Society of Wetland Scientists MOVEMENTS OF FLORIDA APPLE SNAILS IN RELATION TO WATER LEVELS AND DRYING EVENTS Philip C. Darb~',~, Robert E. Bennetts2, Steven J. Miller3, and H. Franklin Perciva14 'Department. of Wildlife Ecology and Conservation and the Florida Cooperative Fish and Wildlife Research Unit University of Florida, Gainesville, Florida, USA 3261 I Florida & Caribbean Science Center 7920 NW 71st St., Gainesville, Florida, USA 32653 3St. Johns River Water Management District P.O. Box 1429 Palatka, Florida, USA 32178 Florida Cooperative Fish and Wildlife Research Unit U.S. Geological Survey, University of Florida Gainesville, Florida, USA 3261 1 Present Address: Department of Biology, University of West Florida 11000 University Parkway Pensacola, Florida, USA 32514 E-mail: pdarby @uwjedu Abstracr: Florida apple snails (Pomacea paludosa) apparently have only a limited tolerance to wetland drying events (although little direct evidence exists), but their populations routinely face dry downs under natural and managed water regimes. In this paper, we address speculation that apple snails respond to decreasing water levels and potential drying events by moving toward refugia that remain inundated. We monitored the movements of apple snails in central Florida, USA during drying events at the Blue Cypress Marsh (BC) and at Lake Kissimrnee (LK). We monitored the weekly movements of 47 BC snails and 31 LK snails using radio-telemetry. Snails tended to stop moving when water depths were < 10 cm; however. there was no apparent effect of water depth on distance traveled in water depths >10 cm. Snails moved along the greatest positive depth gradient (i.e., towards deeper water) when they encountered water depths between 10 and 20 cm. Snails tended to move toward shallower water in water depths 2 5 0 cm, suggesting that snails were avoiding deep water areas such as canals and sloughs. Of the 11 BC snails originally located in the area that eventually went dry, three (27%) were found in deep water refugia by the end of the study. Only one of the 31 LK snails escaped the drying event by moving to deeper water. Our results indicate that some snails may opportunistically escape drying events through movement. The tendency to move toward deeper water was statistically significant and indicates that this behavioral trait might enhance survival when the spatial extent of a dry down is limited. However, as water level falls below 10 cm, snails stop moving and become stranded. As the spatial extent of a dry down increases, we predict that the number of snails stranded would increase proportionally. Stranded Pomacea paludosa must contend with dry marsh conditions, possibly by aestivation. Little more than anecdotal information has been published on P. paludosa aestivation, but it is a common adaptation among other apple snails (Caenogastropoda: Ampullaridae). Key Words: Florida apple snail, Pornacea paludosa, wetlands, dry down, water level, movements INTRODUCTION and wildlife (Darby et al. 1999). It is the almost ex- clusive food of the endangered snail kite (Rostrhamus The Florida apple snail (Pomacea paludosa Say) is sociabilis Vieillot) (Cottam and Knappen 1939), the an integral part of Florida's wetland environments and predominant food of limpkins (Aramus guarauna Lin- is widely recognized as a prey item for wetlands fish naeus) (Cottam 1936), and is prey to a variety of other