Before the arrival of the Europeans there were only a few species of mammals in the Carolines--pigs, rats, and bats. Dogs, deer, and cattle have been introduced to some of the islands by various outsiders increasing variety since the beginning of the nineteenth century. The reptiles are better represented. Crocodiles are found in the swamps of the Palau group and occasionally have been blown to some of the eastern islands but not in sufficient quantity to maintain themselves. A species of iguana is found on Yap. There are many species of lizards and the abhorred toad. Two species of snakes are known in the Palau group. The house fly is all too common as well as other insects. There are also centipedes, scorpions, and spiders.
The Caroline Islands possess fairly important deposits of bauxite and phosphate and minor deposits of a few other minerals. Bauxite is found on Babelthuap, Yap, Ponape, and Kusaie. The deposits in the Ngardamau area of northern Babelthuap are by far the most important. It has been estimated that there are bauxite reserves here of about 50,000,000 tons that run from 52 to 55 per cent aluminum and 20 per cent iron.
The Angaur phosphate deposit ranks as one of the major phosphate deposits of the Pacific. Angaur is a partly raised atoll with phosphate occurring in the old lagoon.
Lesser deposits of other minerals occur on the high islands. Manganese is found on Babelthuap and Yap. Some low-grade coal occurs on Babelthuap near Airai and along the west coast. Some traces of gold have been reported on Babelthuap. The Japanese mined some iron ore on Yap and Ponape. Yap also has minor deposits of copper, zinc, and asbestos.