20.

Round-tailed Muskrat

Neofiber alleni

French: Rat-musqué de Floride / German: Florida-Wasserratte / Spanish: Rata almizclera de Florida

Taxonomy. Neofiber allen: True, 1884, Georgiana, Brevard County, Florida, USA.

Four subspecies are recognized.

Subspecies and Distribution.

N.a.alleniTrue,1884—NE,Florida,USA.

N.a.apalachicolaeSchwartz,1953—NWFloridaandextremeSEGeorgia,USA.

N.a.nigrescensA.H.Howell,1920—CFlorida,includingtheLakeOkeechobee,USA.

N. a. struix Schwartz, 1952 — S tip of the Florida Peninsula, USA.

Descriptive notes. Head—body 186-213 mm, tail 99-168 mm, ear 15-22 mm, hindfoot 40-50 mm; weight 189-350 g (males) and 192-357 g (females). The Round-tailed Muskrat is a large arvicoline but much smaller than the Common Muskrat ( Ondatra zibethicus). Dorsum is dark rich brown, and venter is pale buff. Dorsal hairs are lighter at bases and become darker at tips. The Round-tailed Muskrat is generally similar in form to the Common Muskrat, especially fur, ears, and eyes. Guard hairs in Round-tailed Muskrats form tuft above tail (in contrast to ventrally in Common Muskrats) and stiff hairs on feet increase their surface areas and enhance swimming (similar to Common Muskrats). Hindfeet are larger than forefeet. Diploid number is 2n = 52.

Habitat. Most commonly submerged meadows with water depths of 15-46 cm. Common grasses ( Poaceae) in habitats used by Round-tailed Muskrats are Panicum hemitomon, Leersia hexandra, and Pontederia sp. (Pontederiaceae) .

Food and Feeding. Round-tailed Muskrats eat seeds, stems, and roots of a variety of grasses (especially Panicum sp., Mariscus sp., Sporobolus sp., and Echinocloa sp.) and forbs (e.g. Nymphaea sp., Nymphaeaceae; Pontederia sp.; Iris sp., Iridaceae; Peltandra sp., Araceae; Brasenia sp., Cabombaceae; and Woodwardia sp., Blechnaceae). It is unclear if Round-tailed Muskrats are somewhat carnivorous, with some reporting potential consumption of crayfish (i.e. shells at feeding platforms).

Breeding. Round-tailed Muskrats breed 4-6 times/year when environmental conditions are good, especially adequate water levels and availability of dense and emergent vegetation. Peak breeding is in autumn. Gestation is 26-29 days, and average size of litters is c.2 (1-4) young.

Activity patterns. Round-tailed Muskrats are semi-aquatic and can be active yeararound.

Movements, Home range and Social organization. Density of the Round-tailed Muskrat varies from ¢.50 ind/ha to more than 300 ind/ha, and populations can fluctuate dramatically across years likely due to habitat quality, including water levels. Densities are reportedly highest in sugar cane plantations in southern Florida. In southern Florida, Round-tailed Muskrats occupied ¢.36% of more than 450 isolated wetlands that were surveyed. Local extinction and recolonization occurred frequently. Round-tailed Muskrats make conical houses constructed out of grasses and forbs that are emergent above the water level. Houses are typically spherical or dome-shaped, 18-60 cm or more in diameter, and interior chambers (c.10 cm in diameter) usually have two exit holes. Round-tailed Muskrats also build multiple feeding platforms near their houses that are 10-15 cm in diameter and set on a mat of vegetation above the water level.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Bergstrom et al. (2000), Birkenholz (1963b, 1972), Cassola (2016m), Hafner et al. (1998), Hall (1981), Musser & Carleton (2005), Schantz & Jenkins (1950), Schooley & Branch (2006).