Ten species of aquatic birds nest in the interior wetlands, and six more are known to frequent them. The area also serves as an alternate refuge for a number of species which normally reside in or visit the saline mangrove areas. Although alligators are Sanibel's most spectacular aquatic animal, there are many other important reptiles and amphibians of the interior wetlands. Mammals of the interior wetlands are listed in Chapter 6. Small, freshwater animals are abundant here, and provide food for many creatures.
Insects also are abundant, as are crayfish and mussels in varying quantities.
Mullet, tarpon, Gambusia , bream, bass, and garfish live in the river and provide a bountiful feast for anhingas, crows, ibises, herons, egrets, gallinule and stilts. Condition of the Interior Wetlands Aerial photographs of Sanibel in 1944 show the interior wetlands as broad grassy meadows, with shrubs and trees found only along the two major ridges. Each alteration has interfered with the ecological integrity of the wetlands, and of the island ecosystem. By modifying the native plant, animal, and water systems, the historic habitat diversity has been reduced. The vegetation of the Sanibel wetlands is continuing to undergo rapid change.