Yellow Banana Slug

Small, isolated populations also occur east of the Pacific Coast such as in the inland coniferous rainforests of British Columbia's Columbia Mountains (interior wet-belt), just west of the Canadian Rockies, and have been seen at lower elevations near creeks and damp areas of Mount Revelstoke National Park. Small populations of banana slugs have also been seen along creek and damp areas of the western slopes of the Sierra Nevada mountains to the north of Yosemite National Park in California. Slug densities in these outlying areas in the Columbia Mountains, Sierra Nevada Mountains, and areas south of Santa Cruz are low compared to densities in the coastal coniferous rainforest belt and are rather restricted to damp areas near creeks, ravines, and gullies. This population is probably also a relict from the Pleistocene epoch.
Ecology
Banana slugs are detritivores, or decomposers. They process leaves, animal droppings, and dead plant material, and then recycle them into soil humus. They seem to have a fondness for mushrooms, and they spread seeds and spores when they eat, and excrete a nitrogen rich fertilizer. By consuming detritus (dead organic matter) slugs contribute to decomposition and the nutrient cycles and are an important aspect of the ecosystem.