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Sanibel Rice Rat Monitoring Begins

March 20, 2023

Twice per year, SCCF staff assess the population status of the endemic Sanibel rice rat (Oryzomys palustris sanibeli), a state-threatened rat species found only on Sanibel Island.

Historically, Sanibel rice rats were known to occur in vast cord grass (Spartina bakeri) swales that were once widespread throughout the island.

“These habitats, like others on Sanibel, are being lost to the encroachment of hardwoods caused by human-induced changes to the island’s hydrology and natural fire regime,” said SCCF Wildlife Biologist Mike Mills. “Lack of fire has caused a reduction in open grassy swales that several species, like the Sanibel rice rat, Florida chicken turtle (D. r. chrysea), and various wading birds depend on.”

SCCF staff monitor several remaining swales using motion-activated cameras and specially designed traps called Hunt traps. These baited traps take a photo of the rat next to a measuring tape and allow rats to move in and out freely, without any stress caused by capture.

Trapping occurs biannually in March and November to determine the presence and abundance of Sanibel rice rats and hispid cotton rats (Sigmodon hispidus).

“Long-term monitoring of this rare and state-protected rice rat species, as well as other species such as frogs and aquatic macro-invertebrates, helps us to gauge the health of the swale and the effects of any hydrological changes in the Sanibel River,” Mills said. “The upcoming monitoring season will be important as we assess the effects of Hurricane Ian, which caused saltwater inundation of the island’s freshwater wetlands. The drastic increase in salinity in these areas will undoubtedly affect many species.”


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