Some animals are undoubtedly intelligent. I’ve heard that dolphins may be smarter than humans, read stories about chimps that learned sign language, and I’m amazed by how much a service dog can be taught. However, if you’d asked me about 5 months ago, I would not have said hermit crabs were particularly smart.
Since July, I have been sharing my room with a tank of 4 hermit crabs, and I am fascinated by them. They are extremely agile climbers, and have impressive dexterity with their claws and legs. Though they seem like simple creatures, some of their behaviors are so clearly intentional and shockingly intelligent.
One of the first things the employee at the pet store asked me when I was buying supplies to set up my tank was how many hermit crabs I would be having. When I replied that I’d like three or four, she emphasized to me that I HAD to keep hermit crabs in multiples of two. If I didn’t, she explained, two of the crabs would pair up and bully the other. The social pairing is definitely apparent in my tank. The crabs in my tank are split into two pairs: the twins (named because they chose identical shells), and the dumb one and the big one (aptly named for personality and size, respectively). Though all the crabs generally get along, they tend to be near their partner at all times. Their buddying is subtle at first but very obvious once you know to look for it.
Another process which I think is fascinating in general is molting. When it is time for a hermit crab to shed their skin, the crab buries itself completely in the dirt, and stays buried for up to 3 months. One of my crabs has molted, and another is currently in the process. When the first crab was ready to molt, it dug a hole in the dirt nearly 6 inches deep, almost touching the bottom of the tank. Once it had climbed into the hole, the crab refilled the entrance to the hole. I was already amazed that the crab had covered itself, but I was even more shocked the next morning when the dirt was totally flattened! I am still not sure how they did it, but the crabs somehow managed to pack down the loose dirt until the hole was totally unnoticeable.
By far the most interesting and the most clearly intelligent process that my crabs perform is switching shells. Before even beginning to leave their current shell, hermit crabs thoroughly inspect prospective new shells. The inspection is very methodical and quite fascinating to watch. They use their legs and antennae to feel around the entire outside of the shell, nimbly handling and manipulating the shell to examine it from all angles. Then, they inspect the inside. They stretch partially out of their current shell so that their eyes and antennae can reach inside the shell and determine if it is acceptable. Without fail, once they have looked with their eyes, they use their larger claw to feel the opening of the shell. They also use their claw to gauge the size of the opening. When threatened, hermit crabs pull their entire body into their shell and use their large claw like a door to seal themselves off from danger. So, when looking to switch shells, they consciously use their large claw to determine whether they are large enough to seal themself inside should they encounter danger.
Hermit crabs are surprisingly complicated, smart little creatures. They are fun to watch, they interact well with people, and their behaviors and social structures are fascinating.
I never knew that Hermit Crabs perform such a through inspection of there new shell. I wonder how they find new shells in the wild, or if they go into abandoned shells from other hermit crabs. I feel like I have seen a video hermit crab use something weird as a shell. Anyway, that is so cool that you have hermit crabs. I have had a similar experience at the pet store when I went to get a guinea pig. Originally my dad was only allowing me to get one, however the pet store lady said that guinea pigs should stay in pairs or else one will get depressed. So I left the pet store with two guinea pigs, haha.
I loved reading your post! Even though I feel like I know a bit about animals, they’re so diverse that there’s always more to learn. I’ll admit that I didn’t know that much about hermit crabs, and I certainly didn’t realize how smart they are, so I really enjoyed getting to learn more about them.
I recently read an article that I think is actually pretty related. This article described what I find an interesting but sensical idea – that as humans we tend to see intent/agency when there isn’t any, in other people, other animals, and even sometimes inanimate objects. While I can definitely see this being true, there are nonetheless times when seemingly odd behaviors are intended. And this is exactly what you describe with the ways that these animals act as clearly driven, be it by instincts or by learned behavior. In this way, hermit crabs truly do act intelligently, meaning that contrary to the article sometimes actions with clear intention arises where we don’t expect it.
I would have never thought of hermit crabs to be intelligent. Normally, I would think of them as pretty unsophisticated creatures who like to stroll around the beach and eat. I did not realize there were so many little intricate things when switching their shells or when they are molting. It was very fascinating to read how the crab managed to dig all the way down to the bottom of the cage, fill the holes, and then pack down the loose dirt. In general, that is a pretty hard task to do for many animals and people. I really liked the personal stories, as it reminded me of what it was like to have Betta fish. How they would get very territorial with each other, but greeted other sea creatures.