North of the treeline, food must be caught or killed, not grown. Caribou, snow geese, and Arctic char move constantly, seeking food. Except for a few berries during the brief summer, the Inuit diet originally consisted almost entirely of wild meat, so most of their technology applied to hunting and traveling. The Arctic winter, feared by Europeans, actually made Inuit life easier. The permafrost that keeps trees from growing also keeps melted snow from soaking into the earth; except for scattered eskers and rocky hills, the summer Arctic lies nearly submerged in ponds, or bogs in the form of hummocks that resemble gelatinous bowling balls. In winter, dogsleds easily cover miles of frozen tundra that would require days of walking in summer.