Key Largo Woodrat

Neotoma floridana smalli

Description

The Key Largo woodrat, Neotoma floridana smalli, is a medium-sized rodent just over 1 ft (30 cm) long, including the haired tail. It is somewhat smaller than its near relative the eastern woodrat, Neotoma floridana. Its overall coloration is gray-brown above and white below.

Behavior

The woodrat feeds on plants, nuts, berries, and seeds, as well as on slugs, cicadas and tree snails.

Like other members of its genus, it builds one or more large stick houses for protection from predators and for nesting. The nests are made of dead limbs and sticks, but they may also contain miscellaneous articles (glass, metal, paper, bones) scavenged from nearby. Nests are often used for several generations, growing as large as 4 ft (1.2 m) high and 6-8 ft (1.8-2.4 m) in diameter. The nests are complex, multi-chambered constructions; the interior contains a small globular nest chamber made of plant fibers and grasses. Several entrances lead to the next chamber. One woodrat may utilize several nests, but adults do not nest together. Females have two litters a year, consisting of one to four young with an average of two. Young are born blind between the spring and fall and usually leave the nest after about three weeks, at which time their eyes open. Sexual maturity occurs at about five months of age. Predators are mainly bobcats, foxes, weasels, and owls.

Habitat

The Key Largo woodrat is restricted to undisturbed tropical hardwood (hammock) forests, which represent a climax vegetation type. The closed forest canopy provides a more moderate, humid environment than adjacent grasslands and marshes and supports a rich biota, including many rare plant and animal species. Hardwood hammocks were originally found from Key West north into southern peninsular Florida. Habitat elevation is about 13 ft (4 m).

Species associated with the Key Largo woodrat include the Schaus swallowtail butterfly (Papilio aristodemus ponceanus ), tamarindillo (Acacia choriophylla ), powdery catopsis (Catopsis berteroniana ), and prickly apple (Cereus gracilis var. simpsonii ).

Distribution

The Key Largo woodrat is the southernmost sub-species of woodrat in the United States and is geographically separated from other Florida woodrat populations by over 150 mi (240 km). It is endemic to the hardwood hammocks of Key Largo in Monroe County, Florida.

This species is largely restricted to about 2,100 acres (851 hectares) of forested habitat on north Key Largo. Some of this land is publicly owned, as parts of the Crocodile Lake National Wildlife Refuge and a state resource conservation zone. In 1988, an estimated 6,500 woodrats were thought to exist there.

In 1970, a second, much smaller population was introduced to Lignumvitae Key, where it probably never occurred historically. The population increased from 19 in 1970 to 85 in 1979, suggesting an average annual growth rate of 18%. Though by 1988, the population levels were still quite low there, the relative success of the transplantation demonstrates that introduction of the subspecies into suitable but unoccupied habitat can be an effective management action.

Threats

Because of encroaching residential and commercial development, tropical hardwood hammocks comprise one of the most limited and threatened ecosystems in Florida. The hammocks on north Key Largo represent one of the largest remaining tracts of its vegetation type. In the last two decades, development of the southern two-thirds of Key Largo eliminated woodrat habitat there.

Conservation and Recovery

The most effective conservation measure would be preserving the remaining hardwood hammocks on north Key Largo. The U.S. Fish and Wildlife Service (FWS) and the Florida Department of Natural Resources are engaged in land acquisition efforts that include gaining control of about 630 acres (19.8 hectares) of hardwood hammocks supporting as much as 49% of the estimated total population. The scheduled acquisitions would improve the potential for conserving the remaining populations. However, the species would still be in danger of extinction because the best habitat lies outside these acquisition projects.

Beyond acquiring habitat, recovery efforts must focus on slowing the land development process, even at the expense of infrastructure improvements. In June, 1983, the Florida Keys Electric Cooperative sought a federal loan to construct a power substation that would have provided electricity for up to 6,000 new residential units proposed for northern Key Largo. The housing units were slated for construction in the heart of the last pristine hardwood hammock on the Key. State biologists pushed to add the Key Largo woodrat and the Key Largo cotton mouse (Peromyscus gossypinus allapaticola ) to the federal list under emergency provisions of the Endangered Species Act. The effort was successful, and both species were provided temporary protection in September, 1983, while biologists studied the impact of the proposed substation and housing development. Protection was formally extended the following year, when it was determined that construction would seriously endanger the species' remaining habitat. Subsequently, federal loans for the power project were denied.

In 1986, a proposal to designate Critical Habitat for the woodrat was withdrawn after an agreement was worked out with private landowners that would allow minimal residential development in exchange for wider conservation of hardwood hammock habitat.

The successful introduction of the woodrat to Lignumvitae Key indicates that this species might be able to colonize other areas, such as Key Biscayne National Park in Dade County. While transplantation can be used to supplement other recovery efforts, the FWS deems it a priority to protect the species where it naturally occurs.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
1875 Century Blvd., Ste 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

References

Barbour, D. B., and S. R. Humphrey. 1982. "Status and Habitat of the Key Largo Woodrat and Cotton Mouse (Neotoma floridana smalli and Peromyscus gossypinus allapaticola )." Journal of Mammalogy 63:144-148.

Hersh, S. L. 1981. "Ecology of the Key Largo Woodrat." Journal of Mammalogy 62:201-206.