Onchs: Cutest Slugs on the Shores

Three NAKED Facts

Interactive activity: There are some animals on this rock. Can you find them?

NF#1: See how well camouflaged they are! This is why you should watch your step. You might squash an animal if you're not careful.

Thoughtful question: What do you think these animals are? Worms? Snails? Bugs?

NF#2: Onch slugs are naked snails. That is, they are snails without shells.

Let's look at the underside of one.

See, they have a large broad foot, and a pair of tentacles. Just like other snails. Instead of a shell, they have tough skin.

NF#3: Onch slugs breathe air...through their backside!

Hint to Naked Hermit Crabs: You can sometimes see this backside hole on the underside of an onch. It's (obviously) on the end opposite to the one with the tentacles :-)

Onch slugs belong to the same group of snails like our land garden snails. They have modified gills on their backsides to breathe air. At high tide, they burrow into mud or sand trapping an air bubble to breathe from.

Helpful hints for Naked Hermit Crabs

Onch slugs are more commonly seen on large boulders with a good growth of algae (fuzzy greenish stuff) that they graze on. They are also more plentiful in shady moist parts of the boulder. Or on boulders and hard surfaces under trees. They are more active on cool days. If it is a really hot day, the onchs are probably all well hidden away.

If you can't find the slug, look for the trail of 'processed algae' that it leaves behind. Follow the trail and hopefully you will find an onch at the end :-)

The bigger, flatter, bumpier onch (below) is found on rocks near the low water mark.The smaller, rounder, smoother onch (below) is more often found near the high water mark, usually in shady moist areas on large boulders or rocks with thick growths of algae .
How to Hug an Onch

Be gentle with onchs! Don't force one off a rock if it clings tightly. Choose another one.

Onchs can be darn slippery. Once you manage to get them to un-cling, they tend to drop off suddenly, and as you try to catch them, they squirt right out of your hands. Here is one way to avoid them 'taking the plunge' or losing them among rock crevices. Place a cupped palm UNDER the slug, then gently 'persuade' the onch to let go. It should then fall into your hand.

It is probably best NOT to let visitors handle the onchs. Onchs produce icky slime which might cause problems if kids wipe their eyes or stick slimy hands into their mouths. Also, onchs are rather delicate and kids could injure the onchs.