Next up in my series of posts covering the flora and fauna of the coast redwood understory is a mollusk! You heard that right, a mollusk. It’s the famed banana slug, in our case, the California banana slug or Ariolimax californicus.

The California banana slug, native to the redwood forests of the San Francisco Peninsula, is one of eight or nine species of banana slug that have a range from southern California up to northern British Colombia.

These colorful decomposers are a critical player in their ecosystem, breaking down leaves, other dead plant material, mushrooms, moss, animal droppings and more into rich soil humus.

Banana slugs can grow up to 10 inches long, making them the second largest slug in the world. They have two sets of tentacles, the ones up top for seeing and two down below for feeling and smelling. They have a big hole on their right side called a pneumostome that moves air in and out of their one lung.

They can live up to 3 years (not the 7 years claimed in various places on the internet.) One of the most fascinating aspects of these creatures is that they’re simultaneously hermaphroditic. They can impregnate themselves! or, more commonly, any other banana slug.

They’re all around outside, and even occasionally inside, during the wetter months but move underground and near streams during the dry summers. They can burrow up to 9 feet down into the ground where they estivate, which is kind of like hibernating.

The Calfornia banana slug is an imperiled organism (at high risk of extinction or collapse due to restricted range, few populations or occurrences, steep declines, severe threats, or other factors) and only survives in parts of San Mateo and Santa Clara counties. The slender banana slug, found in the Santa Cruz area is also imperiled.

[Photo credits: Paweł Pieluszyński (via iNaturalist) and me]

close up on a banana slug

close up on bright yellow banana slug

two bright yellow banana slugs crawling on rocks