How fauna has transitioned over time on Sanibel
Sanibel is home to a large variety of faunal species that have changed over time.
“If you compare species that are extant (still surviving), extirpated (locally extinct) or recent additions to the island over the last century, you will notice that there have been several notable changes,” SCCF Wildlife & Habitat Management Director Chris Lechowicz said. “These revisions can be the result of natural events such as hurricanes resulting in wash over events, extended wild fires or prey/foraging loss for various reasons.”
However, manmade changes to the habitat, such as the suppression of fire, changes in hydrology, introduction of exotic species and over-harvesting, also play a large factor.
Since Sanibel is an island, losses of wildlife species are not easily replaced. Historically, faunal migration to the island was slow, even though the coastal areas were not as developed and species were more common.
“Now, coastal areas are mostly developed where fewer species are present resulting in less migration from the mainland,” Lechowicz said.
Established species such as the white-tailed deer, striped skunk and American mink were all extirpated from Sanibel in the 20th Century, mostly due to hunting. It is highly unlikely that they will ever re-colonize naturally. The infestation of exotic species onto Sanibel, such as the green iguana, black rat and Mayan cichlid, were all likely caused from people, whether intentionally or not. Animals such as the coyote and the island’s one black bear likely found passage from “island-hopping” during a low tide, or by the Sanibel Causeway.
“These changes in species richness are caused by a combination of natural and human-induced actions,” Lechowicz said.
Habitat changes, such as the majority of the island succeeding to tropical hammock instead of open canopy grasslands due to fire suppression, has had some positive effects on species such as migrating songbirds and bobcats due to additional cover and food sources. Species such as the eastern coachwhip snake, gopher tortoise and Sanibel rice rat were negatively affected due to their preference for open grasslands.
The storing of water in the Sanibel River from the weir system over the winter benefits aquatic and semiaquatic species, such as alligators, aquatic turtles and game fish species.
Management decisions that directly or indirectly affect the natural habitats on the island must be carefully considered for native species that SCCF seeks to sustain.