During the colonial period the Spaniards, in several efforts to explore the River Frio, were driven back by the Guatuso Indians, who still occupy the greater part of its valley and the slopes of the volcanic mountains. It was not until 1856 that a small expedition penetrated across the country to the Rio Frio from the mouth of the River Arenal, a branch of the San Carlos. They reported fertile, hilly slopes in its upper reaches, and beautiful plains for most of the distance traversed to its mouth. The rubber collectors of Nicaragua for many years have ascended the Rio Frio and other rivers in canoes and plundered the settlements, plantations and property of the Indians, forcing them to retire further up the river. The Guatusos live in _palenques_ (stockades), and their houses are similar to the maloccas among Amazon tribes. Each palenque shelters several families, who cook their food at separate fires built on the ground. They live principally on plantains, yucca, maize, sugar cane, cacao, game and fish, the latter being abundant in the Rio Frio. They also cultivate and smoke tobacco. Their weapons are bows, arrows, stone axes, and wooden knives. They drink _chicha_, made by fermenting roasted green plantains, and also _chicha mascada de maiz_. As the bishop of Costa Rica, Dr. Bernardo A. Thiel, a very noted ethnologist and archæologist, says: “The Guatuso country is probably one of the most delightful portions of Costa Rica. Every tropical product can be grown there in abundance, for the lands are immeasurably rich and the climate one of the best in the tropical belt.” The last census of the Guatuso Indians is as follows: