• About Us

• Contact Us

• Refuge Planning

Wildlife & Habitat

After World War II, the brown tree snake was accidentally introduced into Guam. With no natural predators and abundant prey, the snake population steadily grew and spread throughout the island. As the snakes dispersed, forest bird and fruit bat populations plummeted. By the late 1980s, 12 species of birds and the little Mariana fruit bat had disappeared from Guam. The Refuge provides habitat for the last remaining populations of the endangered Mariana fruit bat, Mariana crow, and the Serianthes nelsonii tree. The brown tree snake is considered the primary cause for the decline of native Guam bird species.

Mariana fruit bat - The "fanihi" is a medium-sized bat measuring 195 to 250 mm from head to rump, with a wingspan of 860 to 1065 mm. The males are slightly larger than the females. The abdomen and wings are dark brown to black with individual gray hairs intermixed throughout the fur. The mantle and sides of the neck are bright gold on most animals but in some individuals, this region may be pale gold or pale brown. The color of the head varies from brown to dark brown.

In northern Guam, bats primarily forage and roost in native limestone forest. Coconut groves and strand vegetation are other plant communities used occasionally for feeding and roosting. In southern Guam, a few fruit bats still inhabit ravine forests. Farms, savannas, and mangroves are habitats that receive little or no use at present but may have been used commonly in the past when bats were more abundant and widespread on the island.

Fruit bat colonies sleep during much of the day, but they perform many other activities as well such as grooming, breeding, scent rubbing, marking, flying, climbing to other roost spots, and defending roosting territories (harem males only). Bats gradually depart colonies for several hours after sunset to forage.

The fruit bat feeds on a wide variety of plant material but primarily on fruits. It appears that the favored foods include the fruits of breadfruit, papaya, fadang, figs, kafu, and talisai and the flowers of kapok, coconut, and gaogao.

Mariana crow - The "aga" is a small black crow with a slight greenish-black gloss on its head, back, underparts, and wings. Its tail has a bluish-black gloss. Females are smaller than the males.

This crow prefers native limestone forest for breeding and foraging, but it will forage in other habitats such as beach strand vegetation and coconut groves. This species is an omnivorous, opportunistic feeder that is known to feed on insects, lizards, bird eggs, hermit crabs, fruits, and seeds.

The remnant population on Guam is restricted in distribution to the northern end of the island, where it most frequently nests in two canopy-emergent tree species. The aga initiates nesting as early as July and as late as March. Its nest consists of relatively large-diameter sticks woven into a platform, small sticks that form the cup, and leaf fibers that line the cup. Clutch size varies from 1-4 eggs, although only 1-2 chicks will fledge. Both adults participate in incubation of eggs, brooding of chicks, and care of juveniles after they fledge. Parents will continue to care for their offspring long after fledging; periods of parental care are known to range from 5 to 18 months. Juveniles may take as long as 3 years before entering into the adult breeding cohort.

Green Turtle (Haggan) - Green turtles (Chelonia mydas) are characterized by a smooth carapace with four pairs of lateral scutes and a coarsely serrated lower jaw-edge. The carapace is keelless and variable brown in color, with darker blotches or patchy markings. The name green turtle is derived not from their external color but from the green coloration of their subdermal fat. Adults often reach a maximum carapace size of about 3.3 ft and weigh approximately 220 lb. Juveniles have streaked dorsal patterns of various colors ranging from yellow-gold to black. Hatchlings have a black carapace and pure white underbody. The carapace length of hatchlings ranges from 1.8 to 2.2 in, with body mass between 0.8 and 1.1 oz

Estimates based on mark-recapture and skeletochonology research indicate that green turtles reach maturity around 20-40 years from birth and are reproductive for approximately 17-23 years estimated a reproductive female can lay about three nests of 100 eggs per season.

While adult green turtles prefer fairly shallow waters, except when migrating to their nesting grounds, juveniles reside primarily in pelagic or open-ocean habitats. When they reach around 8 in carapace length, they move back into shallow feeding habitat. This highly mobile species travels vast distances through incongruent habitats during their periodic migration between foraging and nesting sites. Female are philopatric to specific nesting beaches. Studies have demonstrated that females return, up to 40 years later, to their natal hatching beach to nest.

Green turtles are not obligate herbivores as once believed, but instead feed on seagrass, algae, jelly fish, sponges and other pelagic prey. Hatchlings have been observed eating only invertebrates and fish eggs. Akin to nesting migrations, green turtles often return to the same foraging areas following nesting. Once at these areas, individuals demonstrate strong site fidelity to these foraging sites for extended time-periods. Not all green turtles utilize coastal foraging sites; some remain in the open ocean.

Within the Pacific area, green turtles are found along the coasts of Hawai‘i, American Samoa, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI). The species has been reported as the principal sea turtle in the CNMI. Although Guam breeding populations may not contribute substantially to the overall density of green turtles globally, the island still contributes to the genetic diversity of the species. Ritidian Point is an important habitat for the green turtle, based on numerous sightings, nests and crawls.

Serianthes nelsonii - One of the largest native trees in the Mariana Islands that is found no where else in the world occurs on limestone-derived soils on Rota and Guam. Most of the trees on Rota grow on or near steep hillsides and cliffs at elevations of 490-1,380 feet (150-420 meters) on the western side of the island. Trees in Guam were known to grow at elevations of 400-575 feet (120-175 meters).

The current population estimate for both islands is approximately 122 trees with little or no successful regeneration occurring. It is unlikely that significant numbers of additional trees remain to be discovered on either island. However, continued surveys on Rota and Guam may find a few more individual trees or subpopulations.