Habitat
These fun little guys find their home in the eastern Pacific from Central California down through Baja. If you ever grew up in Malibu California like I did, you may have the distinct memory of digging these guys up from the deeper water on Zuma Beach! Some bigger than the size of my palm!
Instead of the ankle-deep swash where the tiny Pacific mole crabs hang out, the great and friendly spiny mole crabs prefer the subtidal sand just offshore, even as deep as 100ft! Talk about hiding out! Big surf and storms sometimes roll them onto beaches, or maybe they just come ashore to say hello!
Eating Habits
Not a filter-feeder like its smaller cousins, the classic sand crab we all know and love, these guys are scavengers/carnivores! They feed on detritus and shockingly the remains of other Pacific mole crabs! I wonder if they pair that with some fava beans and a nice chianti too?!
In the other direction of the food chain, horn sharks off Baja have been found with diets dominated entirely by spiny mole crabs. Other predators include fish, rays, and opportunistic shorebirds.
Lifestyle
I like to call these tough little fella’s the “armored bulldozer’s of Zuma Beach". They dig backward into sand using powerful, paddle-like legs. Compared with the zippy common sand crab that can usually be found tickling your toes by the shore, the spiny mole crabs are slower burrowers in the crashing swash, which helps explain why they live a bit deeper. After mating, they release larvae that drift through five planktonic zoeal stages before settling back to sandy bottoms.
Fun Facts
- Big Boys!: Adults reach about 65–76 mm (≈2.5–3 in) which is almost the size of your palms!
- Odd roommate: A tiny clam (Kurtiella/Mysella pedroana) often lives inside the crab’s gill chamber as a commensal hitchhiker. Sounds like a Clam of a time to me!
- Same old crab, different niche: They’re close relatives of the familiar sand crabs (all in Hippoidea), but their deeper, calmer zone keeps them out of the daily wave-pounding.
So just remember, next time you’re shuffling your feet in the shoals of zuma beach, there’s a spiny mole crab tidying up the sand just beyond your toes.