Sea rise aids in rabbit decline

By Steve Estes

A recent study done by a pair of University of Florida scientists states that Mother Nature is as much or more at fault for the accelerating loss of Lower Keys Marsh Rabbit habitat in the Florida Keys.

In a study published in late September, researcher Robert McCleery and graduate assistant Jason Schmidt, discovered that nearly two-third of the loss of Marsh Rabbit habitat from 1959-2006 could be attributed to sea level rise instead of the encroachment by human development they expected to find.

That’s not to say that human encroachment into rabbit habitat has played no part in the federally listed endangered species’ road to extinction. It is estimated that only several hundred rabbits currently exist in the Florida Keys, with the bulk of those on land owned by Naval Air Station Key West on Boca Chica. The Navy has utilized a comprehensive habitat management program for more than a decade for the marsh rabbit.

Researchers say there are 13 islands in the Keys, all west of the 7-Mile Bridge, that still host colonies of marsh rabbits. After Boca Chica, the largest herds are found on Big Pine Key and Sugarloaf Key.

That comes as no surprise to rabbit researchers who found that on islands where human development encompassed more than eight percent of the total land mass, the island ecosystem was incapable of producing new rabbit habitat and the animals left in search of better digs.

Actual building, states McCleery, doesn’t seem to be the overriding factor. Instead, he states, it’s the interruption of the migration lanes that would be used by the rabbit to escape the deadly effects of sea-level rise.

As sea level rises, he explains, the traditional habitat transforms into areas marginally suitable, if at all, for rabbit survival. The area where the rabbit would retreat, what would become the new transition zones, is used for human development. The next inland migration takes the rabbit to habitat again only marginally suitable, if at all, for its survival.

Between 1970 and 2000 some of the islands that furnished habitat for the rabbit saw population explosions of more than 10 times where they started, coinciding with the rapid decline of the rabbit. More than 50 percent of the rabbit population is thought to have disappeared in those years, but that is also when scientists noted that sea level rise began to double yearly from under two millimeters per year to over three millimeters per year.

With the acceleration of sea level rise, and the hardened line drawn in the sand by human development, the ecosystem finds itself with nowhere to go, and coastal squeeze results in a net loss of habitat, and the resulting decrease in rabbit population who use the low-lying wetlands and transitional salt marsh as primary habitat.

Due to the increasingly threatened existence of the marsh rabbit, it was one of the species at the heart of the county’s recent overhaul of residential building in sensitive habitat.

Under new regulations, negotiated between the county, US Fish and Wildlife Service, the Federal Emergency Management Agency and environmental groups that sued the latter two for failure to protect species, residential building became much harder in areas where verified marsh rabbit habitat exists, and in the surrounding 500 feet of buffer zone.

USFWS has adopted a policy of limiting human encroachment into what remains of the marsh rabbit habitat and in restoring some natural habitat areas that have transitioned over time into something no longer suitable for the rabbit. There have also been projects to relocate some of the rabbits onto barrier islands where predation is less likely to occur.

USFWS officials claim that of the factors squeezing marsh rabbit populations, feral cats are at the top of the list. The local refuge has been after Monroe County for more than a decade to implement a cat trapping program that would result in free-roaming cats being removed from the islands where rabbits are most plentiful and relocated where they are less plentiful.

The refuge will begin a cat-trapping program on federal lands in the near future, placing all trapped cats with the local animal shelter provider for adoption or euthanization if they are unadoptable due to disease or inability to socialize.

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