Deep in the south Pacific sits a group of five volcanic islands (Tutuila, Aunu’u, Ofu, Olosega, and Ta’u) and two atolls (Rose and Swains) that make up the U.S. territory of American Samoa.
The main island of Tutuila (pronounced too-too-wee-la) is home to 95% of the territory’s population and Pago Pago (pronounced Pongo Pongo), the capital of American Samoa. Many know these beautiful tropical islands only through Somerset Maugham’s short story, Rain, set in Pago Pago or Margaret Mead’s anthropological study, “Coming of Age in Samoa”.
Very few are aware that American Samoa holds one of the United States’ most remote national parks, as well as a national marine sanctuary. The National Park of American Samoa is spread over parts of Tutuila, Aunu’u (Ah-oo-noo-oo), and Ofu (Oh-foo) and includes a coral reef with more than 250 species of coral and 950 species of fish. While the marine areas have a great amount of species diversity, because of the territory’s location 4152 km (2600 mi) southwest of Hawaii and more than 3200 km (2034 mi), species migration from other continents throughout time has been limited and there are many fewer land species. Among the terrestrial organisms, there are only three native species of mammals: two species of flying foxes, or fruit bats and a small, insect-eating bat that is rarely seen.
The fruit bats, Pteropus samoensis, commonly known as the Samoan flying fox, and Pteropus tonganus, the white-naped flying fox, have similar wingspans, ranging from around .6 m to just under 1m, and are distinctive for being active both day and night. It can be difficult to tell one species from another when seen from a distance, but when viewed more closely, they show differentiation in both flight characteristics and in color. P. tonganus has a well defined cream-colored patch on the neck and shoulders, separating a black body and head, while P. samoensis may have either a yellow-white patch on the back of its head, or a mixture of light and dark hairs on the head, giving a grizzled appearance.
Behaviorally, both species exhibit long-term parental care, extending well beyond when the young are weaned and obtain flight capability. However, P. tonganus is found during daylight hours in large roosting colonies that can be made up of hundreds, or even thousands of bats and are arranged according to mating status, while in contrast, P. samoensis usually roost singly, or in mating pairs that suggest possible monogamous mating behaviors.
Not everyone finds the flying foxes so interesting. Some crop damage is attributed to the bats, particularly if fruit is not harvested before it ripens on the trees. And at night, their squeals can be heard as they fight over the flowers of the banana plants. On the positive side, not only are the flying foxes among the major plant pollinators on the islands, at an average of 450 kg for mature adults, they are also the only animals that can carry fruits with larger seeds up the sides of the mountains and over long distances (as much as 40km in a night), helping bare or cleared land to re-vegetate.
No extensive study has been done of the flying foxes of American Samoa. Their natural lifespan is unknown, although captive bats have been known to live as long as 20 years. Although the bats have no natural predators, populations are sometimes depleted by tropical cyclones and hunting. Recovery occurs, albeit slowly. Females are thought to produce only one offspring per year and no one knows the survival rate of the young.
Sources: http://www.nps.gov/npsa/index.htm http://www.nps.gov/npsa/learn/nature/natlhistguide.htm
