Crabs That Have To Act Tough
Male fiddler crabs can be recognized by their huge claw that is used to defend and intimidate other crabs. These crabs live in burrows and their enormous claw has a large role in the defending of their territory. Often, crabs will lose their claw in a battle over a burrow with another crab. These claws do grow back looking identical to their original claw but are not as strong. The crabs recognize that the new claw does not function as well as it’s previous claw had.
Even with this disadvantage, a crab with a new, weaker claw will act as nothing is wrong when faced with a new opponent. The fiddler crab will show it’s claw in a threatening manner as a bluff in order to defend or steal a burrow. A group of researchers collected a sample of these fiddler crabs, Uca mjoebergi, with new claws near
Crabs that were released with the second claw and unable to find an uninhabited burrow generally tried to intimidate smaller crabs out of their burrows. The small crabs fell for the bluff most of the time, vacating the burrow. On the other hand, crabs that had the new claw that were invaded by crabs with an original claw were forced to bluff and if necessary defend the burrow. Since the new claw is much weaker than an original claw these crabs generally would lose if a fight broke out. This shows that the crabs with a new claw were much more successful at bluffing and invading a burrow rather than trying to defend one.
Click here for the original article “Crabs That Fib,” by Kelly Whitlock Burton.
Rob Lubenow (9)
* Updated 10-17-08: The fiddler crabs are aware of the weakness in their claw. After the researchers released the crabs, most of them were more selective concerning which crabs they attempted to intimidate. They went after smaller crabs rather than crabs their own size. This is because they acknowledge that they are not strong enough to fight a crab their own size. The new claw looks identical to the old claw. Crabs are unable to distinguish if another crabs claw is it's original or a weaker claw. This is one of the first study on the matter so their is much more to be learned. Similar studies are being conducted on crayfish, bullfrogs, and hermit crabs.
posted by PWH @ 4:51 PM
10 comments
10 Comments:
This was kind of a sad post, making me feel bad for the crabs that regrow weak claws. Do you know how a crab with a weak claw would react to another crab with a weak claw? It makes me feel bad for those little guys trying to put up a front to their stronger counterparts.
Michele Copeland
I wonder if the crabs are intentionally bluffing or if they don't realize that with their new claws that they arn't as strong anymore.
Jennifer Smith(9)
This is an amazing discovery....i believe the fiddler crabs with new claws are wiser bluffers as result of their previous experiences that lead them to lose their original claws in the first place. But its really unfortunate that the new regenerated claws have a weaker force than the original...
-Joanne Philippeaux
I knew that when a crab loses its claw it grows another one, but I never knew that it was weaker than the original one. Do you know why they grow back looking identical, but are not as strong? How do they know that they aren't as strong? Do they find that out because they have tried to use the new claw or is it something they just know?
-Tara Quist
does the new claw look slightly different than the original claw or different in size? good find!
Hessom Minaei
This is interesting. I wonder if the crabs that end up with a new claw are affected when it comes to mating? Are these crabs less likely to get a female because they cannot fight as well? I also wonder if the crab loses its claw multiple times will it grow back every time? Also does it become weaker and weaker each time that it has to grow a new claw if it can? I would imagine that growing a new claw uses a lot of calories and energy and this could be why the crab ends up with a weaker claw in the end.
Posted By: Lindsay Goodyear
Nice! Since I work with lobsters and green crabs here at UMass, it's nice to hear about a behavior that could potentially occur with others species as well. Is it my understanding that the crabs can also lose a claw in the molting process? Its fairly common for lobsters to lose a claw when they molt and exhibit the same regenerative properties as you were explaining here. How fast does their claw grow back? I would imagine it wouldn't occur overnight, but how long would it take until the crab would be able to "bluff" another crab out of its burrow hole? Thanks.
-Amanda Sceusa
Interesting post! It is so odd that after the crab losses a claw it grow one back that "looks" the same but is functionally weaker. Do you know why the new claw is weaker and not stronger? Is it because the claw has not had enough time to develop as healthy as the original claw?
-Carlos A. Varela
Interesting article choice. I was wondering does claw size have anything to do with finding a mate? Because the males with larger have a higher chance of protecting their territory does factor in attracting the female crabs more?
- Debbie Theodat
That's really neat that crabs can regrow their claws. How long does it take to grow back? How did the researchers measure the force the claws can handle? How much less force could the new claws handle than the old? Is there any way to distinguish between old and new claws? What happens to the crabs without a claw? Do they have to go homeless? Do they have a greater chance of getting killed?
~Allison Cornell (9)
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