Anastasia Island Beach Mouse
Encyclopedia
The Anastasia Island beach mouse (Peromyscus polionotus phasma) is a subspecies of the oldfield mouse
of the southeastern United States
. It occurs in the sand dunes of Florida
and Alabama
beaches. It has been classified by the United States Fish and Wildlife Service
as an endangered species
due to the specificity of its habitat and the natural and human-induced destruction thereof.
in Florida. Though the species once ranged from St. Johns River
in northern Florida to Anastasia Island in southern Florida, habitat destruction limited and eventually eliminated populations in the northern part of the state. The mature, sparsely vegetated, scrubby dunes offer the best burrowing environment, as well as providing the mice with ample food sources. These dunes tend to occur between the high-tide line and the more densely vegetated dunes farther inland. Though sometimes found in the inland dunes, very little foraging takes place there. The mice use the heavy coastal grass cover there to provide protection and avoid detection from predators. Occasionally, beach mice make their homes in abandoned burrows of ghost crabs, but are also capable of creating their own.
), coastal ground cherry (Physallis angustafolia), dixie sandmat (Euphorbia bombensis), tall jointweed (Polygonella gracilis), seaside pennywort (Hydrocotyle bonariensis
), seacoast marshelder (Iva imbricata), and evening primrose
(Oenothera humifusa).
lasts from November to early January, but can continue throughout the year if climate and food sources are optimal. The average litter of pups is 4, but can range in size from 3–8.
is 9 months, mortality is high and most young survive about 4 months.
The indigenous predators include coastal dwellers such as snakes, skunk
s, raccoon
s, and the Great Blue Heron
. Some introduced species
which pose a threat to the mouse are domestic cats and dogs, as well as foxes.
In addition to direct human contributions, increasing hurricane seasons may also be to blame for the vulnerability of the Anastasia Island Beach Mouse. The formation of the sandy beach dunes is due largely in part to the presence of coastal grasses and other plants establishing themselves in the sand. As they emerge from the ground, wind begins to pile sand up at the base of the plants. As the plants grow and the wind continues to blow, these piles increase in size and overlap the adjacent piles and, eventually, dunes are formed. This formation process can take large amounts of time, and as hurricanes increase in frequency and severity, the length of time for dunes to recover and reform before the next storm becomes less and less adequate. While the dunes are in the process of regenerating, beach mice must take up residence in intermediate "matrix
" habitat, which is less ideal for their food foraging and burrow establishing than their eventual dune homes. This, also, puts them more at risk of succumbing to environmental factors.
Reintroduction
is the process of conservationists and park officials setting up a small population of mice in a habitat where it is known to have previously existed. If the potential habitat contains suitable structural features and food sources, and makes the mouse no more susceptible to predators or other potentially harmful factors than their present environment, small populations can be transported and released in the new habitat, with the hopes that they will adjust well and take up residence.
Another option is that of translocation
. Individuals from large, well-established populations can be trapped, relocated, and released into smaller populations in order to supplement their numbers and increase their genetic diversity
. This can not only help boost their population levels, but can actually help the long-term viability of the population by increasing the number of established individuals in the gene pool. This can make the group less vulnerable to diseases and genetic maladies in the long run.
As for people who live in the vicinity of the beach mouse habitat, there are several steps they can take to help ensure the longevity of the species. First, they can become familiar with the plants that serve as anchors for the dunes' sand and make an effort not to disrupt the structural integrity of the habitat. In addition to holding the dunes in place, they also serve as food sources for the beach mouse, so to disturb these plants is to put the entire ecosystem at risk. In avoiding these plants, a good rule of thumb is to remain on paths and trails when walking on or near the beach. Another rule for beach living is to keep cats indoors as frequently as one can, and to never feed stray cats on the beach. With domesticated cats being one of the biggest predator threats to the beach mouse, humans should do nothing to encourage their presence in this environment.
Oldfield Mouse
The oldfield mouse or beach mouse is a nocturnal species of rodent in the family Cricetidae. It is found in the southeastern United States on sandy beaches, in corn and cotton fields, and in hedge rows and open timber tracts...
of the southeastern United States
Southeastern United States
The Southeastern United States, colloquially referred to as the Southeast, is the eastern portion of the Southern United States. It is one of the most populous regions in the United States of America....
. It occurs in the sand dunes of Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
and Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
beaches. It has been classified by the United States Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
as an endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
due to the specificity of its habitat and the natural and human-induced destruction thereof.
Description
The Anastasia Island beach mouse has an average body length of 13.85 centimetre including tail. The coat tends to be a pale tan color with a white underbelly. Subtle white markings can be found across the face and muzzle. Their coloration, being substantially lighter than inland members of their species, is thought to be an adaptation to help them blend into their sandy habitats and avoid predators. Males and non-reproducing females average a weight of 12.5 g (0.4409245263139 oz) and pregnant females have an average weight of 20 g (0.705479242102239 oz).Habitat
The mouse occurs in the sandy dunes of Anastasia IslandAnastasia Island
Anastasia Island is a barrier island which is approximately long located off the northeast Atlantic coast of Florida in the United States. The island is located east and southeast of St. Augustine. It is separated from the mainland by the Matanzas River, part of the Intracoastal waterway, Matanzas...
in Florida. Though the species once ranged from St. Johns River
St. Johns River
The St. Johns River is the longest river in the U.S. state of Florida and its most significant for commercial and recreational use. At long, it winds through or borders twelve counties, three of which are the state's largest. The drop in elevation from the headwaters to the mouth is less than ;...
in northern Florida to Anastasia Island in southern Florida, habitat destruction limited and eventually eliminated populations in the northern part of the state. The mature, sparsely vegetated, scrubby dunes offer the best burrowing environment, as well as providing the mice with ample food sources. These dunes tend to occur between the high-tide line and the more densely vegetated dunes farther inland. Though sometimes found in the inland dunes, very little foraging takes place there. The mice use the heavy coastal grass cover there to provide protection and avoid detection from predators. Occasionally, beach mice make their homes in abandoned burrows of ghost crabs, but are also capable of creating their own.
Diet
The mice eat small insects and coastal plant such as beach grasses and sea oats. They gather seeds which have separated from the plant and blown to the ground. Every night, they leave their burrows to gather the sea oat seeds which have blown to the ground, then return them to their burrows for storage. Due to the highly variable climate of coastal habitats, though, several seasonal plants can offer additional food sources throughout the year, such as the beach pea (Galactia spp.Galactia
Galactia is a genus of flowering plants in the legume family . It belongs to the subfamily Faboideae. They do not have an unambiguous common name, being commonly called "beach peas" or "wild peas".-Selected species:...
), coastal ground cherry (Physallis angustafolia), dixie sandmat (Euphorbia bombensis), tall jointweed (Polygonella gracilis), seaside pennywort (Hydrocotyle bonariensis
Hydrocotyle bonariensis
Hydrocotyle bonariensis once a member of the family Apiaceae, now in the family Araliaceae and of the genus Hydrocotyle is a hairless and creepy perennial.-Description:Flowers: Numerous white to creamy yellow flowers, flower stalks can be ....
), seacoast marshelder (Iva imbricata), and evening primrose
Oenothera
Oenothera is a Genus of about 125 species of annual, biennial and perennial herbaceous flowering plants, native to North and South America. It is the type genus of the family Onagraceae, the Evening Primrose Family. Common names include evening-primrose, suncups, and sundrops.The species vary in...
(Oenothera humifusa).
Shelter
Burrows tend to be constructed at the base of a clump of grass on the sloping side of a dune, and are occupied by either a monogamous, mating pair of mice or a female and her young. The entrance is a small hole, typically 1–2 inches in diameter, followed by a 3–4 foot tunnel of the same diameter. The tunnel leads to a main chamber, which typically has a second 'escape tunnel' leading out the back. The escape tunnel has no opening at the surface, but ends just below the sand's surface. If the mouse's burrow is invaded or disturbed, the mouse will access the escape tunnel and push through the layer of sand at the end to the surface. These burrows are used for food storage, sleeping, and nesting, as well as a refuge from predators.Reproduction
The species is monogamous. Females reach reproductive maturity at 6 weeks and can produce a litter of pups in as little as 20–23 days. The breeding seasonBreeding season
The breeding season is the most suitable season, usually with favourable conditions and abundant food and water, for breeding among some wild animals and birds . Species with a breeding season have naturally evolved to have sexual intercourse during a certain time of year in order to achieve the...
lasts from November to early January, but can continue throughout the year if climate and food sources are optimal. The average litter of pups is 4, but can range in size from 3–8.
Survival
Though the average lifespanLife expectancy
Life expectancy is the expected number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience...
is 9 months, mortality is high and most young survive about 4 months.
The indigenous predators include coastal dwellers such as snakes, skunk
Skunk
Skunks are mammals best known for their ability to secrete a liquid with a strong, foul odor. General appearance varies from species to species, from black-and-white to brown or cream colored. Skunks belong to the family Mephitidae and to the order Carnivora...
s, raccoon
Raccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...
s, and the Great Blue Heron
Great Blue Heron
The Great Blue Heron is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North and Central America as well as the West Indies and the Galápagos Islands. It is a rare vagrant to Europe, with records from Spain, the Azores and England...
. Some introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
which pose a threat to the mouse are domestic cats and dogs, as well as foxes.
Reasons for Endangered Status
Because of the specificity of the dune habitat, the Anastasia Island Beach Mouse is extremely vulnerable to environmental factors. Because of the high real estate values of the coastal habitat of the mice, major commercial and residential development is continually encroaching on the dunes they call home. Humans become a more regular part of the environment, which contributes both directly and indirectly to the endangerment of the mice. Both by visiting, directly interacting with, and subsequently contributing to the degradation of the dune habitat, as well as bringing their domesticated pets into the environment, thus increasing the threat of introduced predators, the overlapping of human and mouse activity is posing an ever-increasing threat to the relatively defenseless mouse.In addition to direct human contributions, increasing hurricane seasons may also be to blame for the vulnerability of the Anastasia Island Beach Mouse. The formation of the sandy beach dunes is due largely in part to the presence of coastal grasses and other plants establishing themselves in the sand. As they emerge from the ground, wind begins to pile sand up at the base of the plants. As the plants grow and the wind continues to blow, these piles increase in size and overlap the adjacent piles and, eventually, dunes are formed. This formation process can take large amounts of time, and as hurricanes increase in frequency and severity, the length of time for dunes to recover and reform before the next storm becomes less and less adequate. While the dunes are in the process of regenerating, beach mice must take up residence in intermediate "matrix
Matrix (geology)
The matrix or groundmass of rock is the finer grained mass of material in which larger grains, crystals or clasts are embedded.The matrix of an igneous rock consists of finer grained, often microscopic, crystals in which larger crystals are embedded. This porphyritic texture is indicative of...
" habitat, which is less ideal for their food foraging and burrow establishing than their eventual dune homes. This, also, puts them more at risk of succumbing to environmental factors.
Conservation Options
There are several conservation options, at both the governmental and the personal level, that can help preserve and recover the Anastasia Island Beach Mouse population.Reintroduction
Reintroduction
Reintroduction is the deliberate release of a species into the wild in zones formerly inhabited by said species but where it has disappeared from for a number of reasons, from captivity or relocated from other areas where the species still survives in...
is the process of conservationists and park officials setting up a small population of mice in a habitat where it is known to have previously existed. If the potential habitat contains suitable structural features and food sources, and makes the mouse no more susceptible to predators or other potentially harmful factors than their present environment, small populations can be transported and released in the new habitat, with the hopes that they will adjust well and take up residence.
Another option is that of translocation
Translocation (Wildlife conservation)
Translocation in wildlife conservation means capture, transport and release or introduction of species, habitats or other ecological material from one location to another...
. Individuals from large, well-established populations can be trapped, relocated, and released into smaller populations in order to supplement their numbers and increase their genetic diversity
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
. This can not only help boost their population levels, but can actually help the long-term viability of the population by increasing the number of established individuals in the gene pool. This can make the group less vulnerable to diseases and genetic maladies in the long run.
As for people who live in the vicinity of the beach mouse habitat, there are several steps they can take to help ensure the longevity of the species. First, they can become familiar with the plants that serve as anchors for the dunes' sand and make an effort not to disrupt the structural integrity of the habitat. In addition to holding the dunes in place, they also serve as food sources for the beach mouse, so to disturb these plants is to put the entire ecosystem at risk. In avoiding these plants, a good rule of thumb is to remain on paths and trails when walking on or near the beach. Another rule for beach living is to keep cats indoors as frequently as one can, and to never feed stray cats on the beach. With domesticated cats being one of the biggest predator threats to the beach mouse, humans should do nothing to encourage their presence in this environment.