HCA: Hermit Crab Association

****POSTED IN BOTH BEHAVIOR AND FOOD**** (please let me know if that is not ok!)

Hello HCA goers!

I am an old time member from my youth (lost that account!) and have had hermits for a very long time (15+yrs!). This semester, I am in a senior level college Animal Behavior course. For our semester project, we had to create and execute research either at the zoo or on any "non-domesticated animal". I decided to design my research around the competition behaviors of hermit crabs. And I could use some additional data.
Here is the setup:
I put a mix of sometimes novel, sometimes routine foods in every afternoon and watch for any takers. Then, I record the feeding behaviors from the start until their "tactic" is ascertained. Tactics are categorized as "avoidance" based resource acquisition-- a hermit crab either avoiding contact with others to grab food or grabbing food and running away with it OR "conflict" based resource acquisition, which includes jostling, chirping, fighting, or any definitive physical contact without withdrawal. I am considering "neutral" behavior in which only one is feeding at a time, since mine have recently not been feeding together (which is unusual for crabs in general but mine in particular). I am correlating this with species, sex, and size of the crabs. I have sexed each crab, measured shield leg width when walking from one leg to another, measured shell aperture, and recorded species and shell type. This way, I can say: medium female C. compressus grabbed a piece of food and ran to a secluded spot to eat. I will likely use names to differentiate, but this will be analyzed with statistical methods.

Why am I posting this here?? Well, I am limited in my sample size. I have a large tank-135g- with only about 9 crabs. Currently, many of mine are down to molt. The ones who are up...lets just say that they seem spoiled and quite lazy about feeding.
I am reaching out here to see if anyone is willing to video the feeding behavior of their crabs and possibly take the sex, leg, and shell type/aperture size measurements to contribute to the data. Any species is fine, so long as you know these data points. I can distinguish between most species but only have C. compressus and C. clypeatus myself. Either embedding a link to a youtube upload or other site with your video would be appreciated. I realize this is a lot to ask--but I figured there would be no better group of enthusiasts to bring this to! This research will likely not be published, but the following question of "What factors influence their feeding tactics" is absolutely a phD or master's thesis worthy question per my accomplished professor. This is essentially a baseline for further research. Credit will be given to anyone participating, and I will provide you with a copy of my research paper.

If anyone is willing, please let me know! I have read many scientific articles about hermit crabs...but there are truly underrepresented in the literature. If anyone simply wishes to say a good luck, feel free to say hello! I can also post the more term heavy description of my research proposal, if anyone is curious

Samantha

I just happened to video this one. The still shot shows you who the are. The smallest greenis a blind male, Stevie Wonder. He must either hear or smell me, and he runs off. The large male on the left took a turn on the hamster wheel for a good 10 hours and I believe he was a little hungry. Large female on the right, I only have 4 males out of 15 PPs so odds are the med green/brown shell is female but I can't be certain. They were eating a bunch of seeds and nuts, most lively.

I have a video of the event, about 45 seconds if you want it. And I'd be happy to video future feedings if it helps.

However taking measurements, etc is probably going to be your Achilles heel. As a rule, it's a hands-off kind of hobby. I photograph and sex mine as I adopt them but after that, I leave them be. I don't know how you're going to take measurements from a crab retreated deep in a shell.. Stevie now runs from me because I picked him up ONCE after I put him in the cage to gauge the extent of his blindness. All I did was hold and observe him for a few minutes and now he runs every time he thinks I'm around. There are only a couple who aren't terrified of my giant hands but if I start wrangling them every time they eat to verify the rest....I'll never see any if them again!

It would be easier with a small population of easily distinguishable crabs, but then again, population size would affect the results too I think. I imagine it's different with 3 crabs vs 30. Plus, mine all get along, but new crabs introduced into a set colony all go through a hazing period which can affect feeding behaviors as well. My smaller ones defer to the larger in the beginning while the larger ones push and shove until someone "wins" or they get bored.

If I can help, let me know but I'd probably change my experiment to naked mole rats instead!

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VickieG wrote: ↑

Wed Apr 21, 2021 10:42 am

I just happened to video this one. The still shot shows you who the are. The smallest greenis a blind male, Stevie Wonder. He must either hear or smell me, and he runs off. The large male on the left took a turn on the hamster wheel for a good 10 hours and I believe he was a little hungry. Large female on the right, I only have 4 males out of 15 PPs so odds are the med green/brown shell is female but I can't be certain. They were eating a bunch of seeds and nuts, most lively.

I have a video of the event, about 45 seconds if you want it. And I'd be happy to video future feedings if it helps.

However taking measurements, etc is probably going to be your Achilles heel. As a rule, it's a hands-off kind of hobby. I photograph and sex mine as I adopt them but after that, I leave them be. I don't know how you're going to take measurements from a crab retreated deep in a shell.. Stevie now runs from me because I picked him up ONCE after I put him in the cage to gauge the extent of his blindness. All I did was hold and observe him for a few minutes and now he runs every time he thinks I'm around. There are only a couple who aren't terrified of my giant hands but if I start wrangling them every time they eat to verify the rest....I'll never see any if them again!

It would be easier with a small population of easily distinguishable crabs, but then again, population size would affect the results too I think. I imagine it's different with 3 crabs vs 30. Plus, mine all get along, but new crabs introduced into a set colony all go through a hazing period which can affect feeding behaviors as well. My smaller ones defer to the larger in the beginning while the larger ones push and shove until someone "wins" or they get bored.

If I can help, let me know but I'd probably change my experiment to naked mole rats instead!

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I would love to see the video interactions of them feeding! Taking your best guess at sizes and sexes is fine, but not ideal. Obviously, the welfare of your pets is a top concern of mine, so don't do anything you don't want to! Personally, my crabs are accustomed to being handled and don't spook very easily. I am pretty patient and gentle when handling them, so they know have a significantly shorter withdrawal duration, which has be conditioned over time.
Any contribution you would like to give is much appreciated! Studying invertebrate behavior is actually much easier than studying vertebrates, who have complicated social behaviors and very, very long ethograms. I picked them because I have seen feeding competition often...when enough crabs are up that are willing to compete
Also, I am really interested in your blind crab--how do you know he is blind? Does he seem compromised by it? I know tactile signals are the primary locomotion signal for them (think antennae and hairs), so I am curious as to how his behavior is modified!

I too would have a hard time measuring, but I have a funny clip to contribute...

This is a short video of my largest PP pushing another one off the food dish. Lol.

The larger one is female (Hermione) and she’s considered a large I think, wearing 1 & 1/4” shell opening. She’s pretty chill, but definitely seems to be in charge. She loves to play on the wheel!

The smaller one is male (Turbo) and he’s a medium I think. He’s usually very active, loves to dig and climb and is the least shy.

//cloud.tapatalk.com/s/6083769ec60 ... T-food.mp4

Hope you can see it! Let me know if you have any questions and good luck with all this!


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crabbycasey wrote: ↑

Fri Apr 23, 2021 8:40 pm

I too would have a hard time measuring, but I have a funny clip to contribute...

This is a short video of my largest PP pushing another one off the food dish. Lol.

The larger one is female (Hermione) and she’s considered a large I think, wearing 1 & 1/4” shell opening. She’s pretty chill, but definitely seems to be in charge. She loves to play on the wheel!

The smaller one is male (Turbo) and he’s a medium I think. He’s usually very active, loves to dig and climb and is the least shy.

//cloud.tapatalk.com/s/6083769ec60 ... T-food.mp4

Hope you can see it! Let me know if you have any questions and good luck with all this!


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Ah! This is actually perfect and exactly the kind of thing that I need! May I ask what was recording this? It is a great instance of some confrontational competition behavior. Like you say, a good shove, which is funny but also useful!
Thanks for taking the time to respond I wish my own crabs were being cooperative enough to do things like this instead of the current punks and mass molters This is the kind of instance that made me choose this topic for them.

Oh I’m so glad! I have a Wyze cam with night vision. I capture quite a lot with it. Watched 3 hours of one of mine (Gary) going after poor Turbo for his shell...and was finally able to get him out of it, it was crazy to watch!

I will gladly keep my eye out for things revolving around their food dish and post them here for you!


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