Florida mouse

Florida mouse Temporal range: Late Pleistocene – Recent
Conservation status
Vulnerable  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Cricetidae
Subfamily:	Neotominae
Tribe:	Reithrodontomyini
Genus:	Podomys Osgood, 1909
Species:	P. floridanus
Binomial name
Podomys floridanus (Chapman, 1889)
Synonyms[2]
Hesperomys floridanus Chapman, 1889 Hesperomys macropus Merriam, 1890 Sitomys floridanus: Chapman, 1894 Peromyscus floridanus: Bangs, 1896 Podomys floridanus: Carleton, 1980

The Florida mouse (Podomys floridanus) is a species of rodent in the family Cricetidae. It is the only species in the genus Podomys, which is the only mammal genus endemic to Florida. The Florida mouse (also known as the big-eared deermouse, the Florida deermouse, and the gopher mouse)^[3][4] is found only in a limited area in central peninsular Florida and in one small area in the Florida panhandle. The mouse inhabits some of Florida's hottest and driest areas in the high pinelands, sandhills, flatlands, and coastal scrub.

The mouse is an omnivore, measures 195 mm (7.7 in) in total length, has relatively large ears, and displays brown to orange upperparts and white underparts. The mouse breeds throughout the year, and raises its two or three young per litter in the nesting chambers and passages it constructs in the burrow of the gopher tortoise (Gopherus polyphemus). Real estate development and a decline in the gopher tortoise population threaten the mouse's future. The species is listed as Vulnerable by the IUCN.

Description

The Florida mouse displays a soft and silky pelage, brown above and orange on the cheeks, shoulders, and lower sides. Underparts are white. The young are gray. The species has a skunk-like odor.^[5] The mouse has relatively large, nearly naked ears (16 mm long or more), a relatively short tail approximately 80% of total body length, and large hind feet (24 mm long or more) with five, rather than the usual six, plantar tubercles.^[2][5] There is no difference in appearance between males and females.^[3]

The appearance of the Florida mouse is similar to the Peromyscus shown in this illustration

The mouse looks like Peromyscus, and was once placed as a monotypic subgenus in the genus Peromyscus The greater size and distinctive coloration of Podomys floridanus distinguish it from the cotton mouse (Peromyscus gossypinus) and oldfield mouse (Peromyscus polionotus), which also occur in Florida.^[2][5]

In 1973, a biochemical polymorphism study was conducted in four sample areas of the species. Electrophoretically demonstrable variation was found in one or more populations at 15 of 39 (38%) of the loci examined, and two and sometimes three alleles per locus were detected. At the least, the findings give an indication of the kind of genetic variation that may be found between populations within a species. The amount of variation was similar to findings in examinations of Peromyscus polionotus, Sigmodon, and Dipodomys.^[5]

Average measurements reported in 1993 of 30 adults were: total length 195 mm (7.7 in) 178–220 mm (7.0–8.7 in); tail 88 mm (3.5 in) 80–101 mm (3.1–4.0 in); hind foot 26 mm (1.0 in) 24–28 mm (0.94–1.10 in); ear 19 mm (0.75 in) 16–21.5 mm (0.63–0.85 in). The diploid number is 48 and dentition 1/1 0/0 0/0 3/3 total 16.^[5]

Taxonomy

The mouse was first described by Frank Chapman in 1889 in a paper in the Bulletin of the American Museum of Natural History, from a specimen collected at Gainesville, Florida.^[6][7] The species was named as a separate subgenus of Peromyscus by Wilfred Hudson Osgood in 1909, but generic recognition was disputed in the 1980s. Michael Carleton and Guy Musser supported the ranking in 1993.^[8] No subspecies have been described.^[6]

Distribution and habitat

Dry places such as sandhills are common habitats for Podomys.

Podomys is the only mammal genus endemic only to Florida.^[2][5] The Florida mouse is found coast to coast in central peninsular Florida. An isolated population is found in the Florida panhandle at Franklin County, Florida.^[2][5] The species occurs from north-central Florida south to Highlands County and Sarasota County. It is found along the Atlantic coast from St. Johns County south to Miami-Dade County.^[9]

The mouse inhabits some of Florida's driest locations. It is common in the sand pine (Pinus clausa) scrub and the high pinelands of turkey oak (Quercus laevis) and longleaf pine (Pinus palustris), and is found in the slash pine (Pinus elliottii) and turkey oak habitat of the southern ridge sandhills, and in scrubby flatlands, and in coastal scrub associations.^[5] Home ranges average roughly 1 acre (0.40 ha),^[1] and are smaller in the flatlands. Populations are greater in the scrub and flatlands than in the highlands.^[6] Its largest populations may occur within Ocala National Forest and the scrubs along Lake Wales Ridge.^[9]

Behavior

The Florida mouse is nocturnal,^[3] and is active throughout the year except on especially cold nights.^[9] The mouse can climb, but is primarily a terrestrial species. In laboratory experiments, P. floridanus used its forepaws to dig and throw substrate backwards while other species mainly used their hindfeet to do the same.^[4]

Shelter

Gopher tortoise burrow entrance

The Florida mouse has been called the gopher mouse because it shares the long, deep burrow of the gopher tortoise (Gopherus polyphemus). The mouse makes nest chambers, small side passages, sometimes a pad of oak leaves and wiregrasses for chamber floors, and small chimney openings in the roof of the burrow. It uses these openings, the main entrance, and side passages for entrance to and exit from the burrow.^[10] In the absence of gopher tortoise burrows, the mouse will use those of the oldfield mouse (Peromyscus polionotus) or will make its own.^[9]

Diet

The Florida mouse is an omnivore and its diet consists of acorns when available, insects, seeds, nuts, fungi, and other plant material and vertebrates.^[1][11] A 1987 report indicates the mouse feeds on engorged ticks (Ornithodorus turicata americanus) that parasitize gopher frogs (Rana areolata) and gopher tortoises.^[11]

Reproduction

Florida mice breed throughout the year with a peak between July and December, a lesser peak in January and February, and a lull or cessation in April and May. Unlike most murids, copulatory behavior lacks intravaginal thrusting, the intromission thrust is more intense than the dismount, there is no lock, and ejaculation occurs with every thrust.^[4]

Gestation is about 23 or 24 days.^[12] The mice dig side burrows off the main burrow of the gopher tortoise, line them with shredded plant material, and use them as nurseries.^[3] In eight litters of young conceived in the wild but born in the laboratory, litter size numbers varied from two to four for an average of 3.1 per litter.^[12] The young are born in nests in the burrow.^[1] Newborn weigh 1.9–2.9 g (0.067–0.102 oz) and measure in total length 44 mm (1.7 in); tail length 12 mm (0.47 in); and hind foot length 8 mm (0.31 in). Teeth begin appearing on the fourth day, the young are active and agile about the 10th day, and the eyes open about the 16th day. Nursing is virtually non-stop for the first two weeks of life.^[3] Weaning occurs at three to four weeks, and the young display adult behavior at this time.^[12]

Survival

Ectoparasites are seven species of mites, five ticks, five fleas, a louse, and the subdermal botfly larva, Cuterebra. Known endoparasites are three species of protozoans found in fecal smears, one trematode, four cestodes, seven nematodes, and nymphal pentastomids found in various internal organs.^[6]

In 2010, exact population size was unknown, but estimated to be in the several thousands and decreasing.^[1] Presumed predators are snakes, birds of prey, bobcats, raccoons, and foxes. A high number of shortened tails have been observed in the mice and a modified integument in the tail facilitates tail loss, probably as an anti-predator mechanism.^[6]

Few wild individuals have a lifespan of over a year, though captive individuals may live for several years.^[1] One captive male lived seven years, four months.^[6]

Relations with humans and conservation

The species in all probability has little or no direct impact or influence on human interests and concerns but agricultural and real estate development are a threat to the species' very narrow habitat. Collecting specimens in the dry ridges is complicated by the millions of ants which eat the bait in the trap the moment it is set on the ground. Live collecting is the alternative, but the bait is usually digested by the time the animal is taken from the trap, making food research difficult if not impossible.^[6]

As early as 1998, the Florida mouse was a federal C2 candidate taxon, and considered Threatened by the Florida Committee on Rare and Endangered Plants and Animals. The mouse was named a Species of Special Concern by the Florida Game and Fresh Water Fish Commission.^[8] The Florida mouse inhabits a restricted habitat in the United States and that habitat is threatened not only by agricultural and real estate development but by wildfire suppression. Habitat decline is expected to continue into the future.^[1][6] The mouse is dependent upon gopher tortoise burrows, but disease and habitat loss are responsible for decline in the tortoise population.^[1] Red imported fire ants (Solenopsis invicta) threaten both tortoise and mouse populations. The IUCN has listed the species as Vulnerable and recommends further study of the species, maintenance of viable populations of gopher tortoises, and the preservation and management of suitable habitat for the species.^[1] The mouse is protected on several conservation lands across central Florida.^[9] Occurrences of the Florida mouse are protected at Archbold Biological Station, Ocala National Forest, and others.^[1]

References

Footnotes

Literature cited