The twin menaces of hurricanes and beachfront development appear poised to wipe out Florida's most diminutive coastal native, the beach mouse, according to new research led by a University of Florida scientist.
Scientists at UF and Auburn University have concluded that the few remaining populations of beach mice on the Florida and Alabama coasts are in "substantial danger" of extinction from hurricanes and continuing loss of habitat to development.
In research on four remaining populations -- including the last known populations of a Perdido Key subspecies -- the researchers predicted the populations have a 37 to 57 percent chance of extinction in 25 years and a 59 to 80 percent chance in 50 years.
Their conclusions already are being borne out: Since the research was conducted, one of the Perdido Key populations has gone extinct, although another population of the subspecies has been reintroduced elsewhere on the key.
"We asked, 'What would be the chance that beach mice will persist in the future if we consider the effects of catastrophic events such as hurricanes?'" said Madan Oli, a UF assistant professor of wildlife ecology and conservation and lead author of a paper on the research that appeared this year in Biological Conservation. "Unless we increase our efforts to conserve habitat and take other measures, the answer doesn't look too good."
The beach mouse, Peromyscus polionotus, is small and nocturnal. It ranges in color from nearly white to brown, depending on the color of the surrounding soil. The mice once occurred throughout the coastal regions of Alabama and western Florida, but the spread of commercial and residential development has slashed their numbers and fragmented their populations.
Today, only about a dozen small populations remain on the Gulf coast, composed of four endangered subspecies and one not listed as endangered or threatened.
Oli, Nicholas Holler of the Alabama Cooperative Fish and Wildlife Research Unit and Michael Wooten, an associate professor of biology at Auburn, focused on four populations near the Florida-Alabama state line.
Two, consisting of the Alabama subspecies, were at the Bon Secour National Wildlife Refuge in Alabama, one at Fort Morgan and one in the center of the refuge.
The other two, consisting of the Perdido Key subspecies, were located on Perdido Key at Florida Point and Johnson Beach. The one at Florida Point is now extinct, although biologists have successfully introduced another population nearby.
To gauge the populations' chance of survival, the researchers drew on data gathered by Wooten and other scientists who had spent several years in the 1980s and 1990s using live traps to collect and count mice at the sites. They analyzed the data with computer models using a method known as population viability analysis.
Their results are not promising. For one thing, the scientists' estimates of actual numbers of remaining mice are quite low. At only one of the four sites did estimates top 1,000 mice during the six or more years when the populations were sampled, while low numbers for the years reached 50 mice or fewer for all the sites. Large population fluctuations are typical of small mammals, but the pattern is dangerous for beach mice because their already low numbers mean a dip in the population can prove a fatal blow, the scientists said.
"I think if you take a particular population, almost any of them has a high probability of extinction within 100 years - that's probably a normal function of their biology," Wooten said. "It's just that now, with so few populations, that fluctuation poses a threat to the species."
The problem is that hurricanes have the potential to wipe out mouse populations -- thanks to coastal development, Oli said.
On undisturbed lands, beach mice live on dunes, but retreat to nearby scrub dune habitat when a hurricane destroys their burrows or temporarily eliminates seeds such as sea oats that constitute their diet, Oli said.
While most frontal beach zones remain intact, scrub habitat is ideal for beachside development and has become increasingly scarce as condominiums and houses sprout along the coast. As a result, the mice have no refuge.
Not only that, in undisturbed areas, mice living in scrub habitat can repopulate frontal dunes after catastrophes, whereas if the scrub is gone, that option is closed off.
Oli said conservation strategies could help. For one thing, the state or federal government could work to conserve essential scrub habitat. Also, he said, re-establishment of mice populations in adjoining suitable habitats will provide some protection against total loss.
Wooten said protecting the beach mouse will ensure protection of areas that are not only attractive to people but also home to an array of other plants and animals.
"You're saving beautiful as well as valuable habitat," he said. - By Aaron Hoover
[Contact: Michael Wooten, Madan Oli, Aaron Hoover ]