As is characteristic of pelagic islands, indigenous fauna is limited. The only mammal native to the islands is the bat, two species of which are found in the Marianas, and one in the Bonins. One of these, the fruit bat, is used as food in the Marianas; it is caught in the forest and along the cliffs at night with long-handled nets. Geckos are found throughout the entire chain, and the iguana in the Marianas. The only land snake is a small, harmless burrowing variety about 5 inches in length and resembling an earthworm. Sea snakes are common and a constant hazard to wading fishermen. Insect and bird life is abundant. Introduced rats have become a major problem. Agriculturally, the two chief parasites are the coconut beetle, which has damaged the palms on Saipan, Tinian, and Rota, and the African snail, which attacks all types of plant growth.
Both the Bonins and the Volcanoes were uninhabited at the time of discovery. The Marianas were occupied by the Chamorros, a race of Mongoloid stock but of obscure origin. They were described by Pigafetta as having "blacke beardes and blacke heare on theyr heades which they weare longe downe on theyr wastes. They are of the same stature that we are, and well made, of coloure lyke vnto an olyue. Theyr women are well fauored with blacke and thick heare on theyr heades reachynge to the grownde."
Specifically when, by what route, and from what area the first inhabitants of the Marianas came is unknown. Study of their cultural traits as reported by early voyagers indicates that the ancestors of the Chamorros probably came from the Malayan area, that their movement was late in the Pacific migrations, and that they moved by way of western Micronesia and perhaps the Philippines. Some racial elements may have also been added by way of the island routes from Japan. At the time of discovery, the natives practiced a gardening, fishing, and collecting economy. Evidence of their material culture includes neolithic stone tools, bone implements, pottery, and the "latte," double rows of capped pillars, which are believed to have served as supports for houses and canoe sheds.
The prehistoric landscape was largely a wooded one broken here and there by villages and garden lands. Settlement was mainly along the coast in villages of 50 to 150 huts; interior villages were smaller, seldom consisting of more than 20 buildings. The houses were raised on piles and constructed with thatched roofs of coconut leaves. Rice was grown in the stream valleys and marshes; bananas, sugar cane, breadfruit, taro, and coconuts on the higher land. Though rice was a preferred food, land suitable for its growth was limited. It apparently was grown only on Guam, Rota, and Saipan. Fire was probably used in clearing, and the fields were abandoned as the soil became depleted. Tillage was accomplished with digging sticks and a kind of stonebladed hoe. In their limited and restricted island area, the Chamorros pressed every possible item of their environment into use within the limits of their culture level. Edible foods such as yams and arrowroot were collected from the jungle; birds and bats were captured for food; fish, crabs, and turtles formed part of their diet.
Today no pure-blooded Chamorros remain, and their culture has been profoundly altered. The native peoples are a mixture of many strains, chiefly Spanish and Filipino, but also German, Japanese, and American, with traces of other nationalities added during the whaling days. In the long period of Spanish rule, acculturation brought many changes in the native manner of living. Some original culture forms such as language have persisted, and certain personality traits remain. American ideas have been strong on Guam. In the other Marianas, German rule was brief and left little cultural imprint. The Japanese sought to reshape native attitudes and habits to fit into the socioeconomic structure established on the islands with colonization and commercial development. The natives became a minority group surrounded by the Japanese and an imported culture, but the total amount of influence was small. Throughout the Mariana area, the pattern of life is still basically a combination of Spanish and native elements.