Transcript:

Today on Animal Fact Files we’re talking about hermit crabs. Most people know them as the funny little creatures they see in just about every pet store, but these crabs come in all shapes and sizes. First off, they’re technically not even true crabs. Hermit crabs different from true crabs in that their rumps are rather soft and don’t come with the complete, hard exoskeleton found in true crab species. This is why many types of hermit crabs utilize the shells of other animals for protection - but even that isn’t always true!

There are hundreds of hermit crab species, and, contrary to their namesake, they aren’t loners. Some species of hermit crabs can be found living in colonies of more than 100 individuals! So why they got a common name like “hermit” doesn’t really make sense to us...

Some hermit crabs live on land, though they still need access to water to survive; some live in water, though they can venture onto land in short spurts; some live in the deep ocean and are hardly ever even noticed by people; some are left-handed… or… clawed? Anyway you get the idea. They aren’t all just the cuties hanging out in terrariums. In the wild, hermit crabs live throughout the world’s oceans and coastlines, though there are even some freshwater species, too! The most common and well known hermit crabs prefer coastal areas. Land dwelling hermit crabs tend to live in sandy areas close to shore. They may hide under the sand, in leaf litter, or beneath rocks during the day and come out during the cooler nighttime hours. Marine hermit crabs are usually found in reef communities or seagrass beds, but deeper water species can live along oceanic trenches reaching more than a mile (1.6 kilometers) deep!

Regardless of where they live, most species of hermit crabs need to find a shell to call home. Hermit crabs don’t make their own shells and from a young age depend on the shells of other animals in order to survive. Hermit crabs are commonly seen in marine snail shells, but they can also utilize the shells of bivalves and sometimes even use rocks! Of course, not all hermit crabs do this. Taxonomically speaking, the coconut crabs we’ve discussed in a previous episode are hermit crabs, but they don’t use a shell - they’re so big, they probably couldn’t find one anyway!

Hermit crabs don’t begin life with a shell. Larvae hatch from eggs that are usually carried around by their mother for a period of time. Breeding habits in hermit crabs can differ significantly with the species, but in land dwelling hermit crabs the female carries the eggs around until they’re ready to hatch at which point she’ll soak them in water and the newly hatched larvae will be pulled out to sea by the tide. The larvae will develop in the ocean, molting as the grow larger. When they’re at an appropriate size, which can depend on the species, the hermit crabs will find their first shell, crawl in, and go on their way. Of course, as they grow they’ll need bigger shells. Often there aren’t many empty gastropod shells just lying around, so hermit crabs will actually trade with one another to help ensure they get the sizes they need!

The shells in land dwelling hermit crabs are used to retain water as they traverse beaches. Though they’ve adopted a terrestrial lifestyle, these hermit crabs still require moisture on their gills to stay alive, so they just carry their water with them! In marine hermit crabs, their shells can act as landing sites for other animals. One species of marine hermit crab will purposefully collect a sea anemone and attach the cnidarian to its shell. It’s a mutual relationship because the anemone provides protection and the hermit crab provides food.

Hermit crabs will eat just about anything. They’re scavengers and will happily munch on both plant and animal material whether or not it’s alive or dead. Hermit crabs themselves are eaten by sea gulls, sea stars, crabs, fish, octopuses and more - including each other if times are tough. In the wild, if they can avoid being eaten, some hermit crab species can live decades while others may survive just a few years!

For more facts on hermit crabs, check out the links in the description. Thank you to jacoby lavan for today’s request. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!