Lots of people wonder how big can hermit crabs get, but the funny thing is that since there are over 1100 species of this animal, sizing can be a little difficult. So, first let’s go over some hermit crab basics then let’s talk about the size of various species out there. Keep in mind, the size of the hermit crab in question will depend on the particular species in question.
Hermit Crab Basic Facts
- There are over 1100 species of hermit crabs in 120 genera.
- Hermit crabs have long and spirally abdomens. Unlike other crabs which have hard exoskeletons or shells, hermit crabs have a soft shell, leaving them vulnerable to attack.
- Since hermit crabs do not have a hard shell, the overwhelming majority of them use mobile homes. In other words, they find discarded shells of other animals and inhabit them.
- The abdomen of a hermit crab is specially designed to be able to clasp and hold onto the inside of a shell. The shell needs to be big enough for the hermit crab to fully retract itself into it, or else it will be left vulnerable.
- The species is not the only thing which determines the size of a hermit crab. The shell they choose to live in will also decide the size to a certain extent. A larger shell will make a hermit crab grow faster and bigger, whereas a shell that is too small will keep it fairly small.
- There are two main groups of hermit crab species. The first kind is the marine hermit crab, which spends most of its time underwater, usually salt water. They can go on land for brief periods of time as long as their gills are wet. The second group of hermit crabs is the land hermit crab. While they do spend most of their time on land, they do need access to fresh and saltwater to keep their gills damp and able to take in oxygen.
- Hermit crabs can grow anywhere from a few centimeters in size all the way to the size of a large coconut. Once again, this depends on the species in question.
- Hermit crabs molt several times per year. This means that they are growing and they shed their old shell (as well as their mobile shell) in order to grow larger. This process can keep going on for quite some time, and each time they will grow bigger.
- Hermit crabs can live anywhere from 10 to 70 years, with the ones that live longer usually also growing the largest (because they never stop molting).
Hermit Crab Species & Size
So, now that we have some of the hermit crab basics out of the way, let’s talk about some of the different species, specifically their size. Keep in mind that this is very general because the size of the crab will also depend on how long they live as well as the size of their shells.
Scientifically named Coenobita clypeatus, the Caribbean crab can grow to be anywhere from 2 to 6 inches in length from front to back, with one claw being larger than the other. They tend to be deep purple and brown in color, a tan head, and a little red or orange on them. They favor shells which have round openings. This is a land based crab and it is one of the main ones found in pet shops.
The Ecuadorian hermit crab, scientifically named Coenobita compressus is another main land hermit crab species that can be found in pet stores. These are some of the smallest ones around, only growing to around 12 mm or ½ inch in size.
The strawberry hermit crab is also known as Coenobita perlatus. Not only are they called strawberry hermit crabs because of their red coloring, but because their body shape also resembles it. Also, these things can grow to be around 12 to 15 cm in size (up to 6 inches).
Ruggie crabs, also known as Coenobita rugosus are fairly small and are usually known to grow to only around 6 cm in size.
This is not a type of hermit crab you want at home. The Birgus latro or coconut crab can grow to be up to 5 kg heavy (11 pounds), and can grow to be up to 1 meter in length from leg to leg. They are big, heavy, and can be pretty mean too. This is a land hermit crab and will actually die if submerged in the water. It is also one of the few that stops carrying other shells as an adult because it develops its own hard exoskeleton.
You might also like our post on the best sand for Hermit Crabs here.