Dishonest Crabs

2010/03/08
By Collin

Photo by Denn

When I hear dishonesty I think of lying. It turns out that other animals besides humans can lie, too. When I hear that, I think no way, but scientists from Australia have found out that there is dishonesty in the animal kingdom. The dishonest animal is only two centimeters across, the fiddler crab.

The fiddler crab has one giant claw which it uses to attract mates and fight rivaling males. If the big claw is lost it can always grow a new claw. This is where the lying comes in. During the growth of the claw, the crab’s body says there is a “cheaper” way. They make the claw bigger but they also make it lightweight and toothless. Dr Simon Lailvaux of the University of New South Wales says that the interesting thing is that other males can’t tell them apart. Before a fight the crabs display their big claws which is important to the process.

The study is important because it helps us understand more about dishonesty among animals. The thing is it is hard to pick up on it. It is hard because dishonest signals are supposed to be hard to catch on to. Lailvaux said “By studying how animals fight we can learn what physiological and performance capacities enable males to win fights, we’re getting closer to identifying which traits are likely to be generally important for male combat.”

Can these crabs lose their claw multiple times and if so do they get weaker each time? Are there other animals that can bluff in a similar way as the fiddler crab? How are fiddler crabs able to re-grow their claws?  Can this be used to help humans?

  • Adam

    Great post Collin! Fiddler crabs are some of my favorite animals and I’m so happy that you’ve written a post about them. I had no idea that they can regenerate body parts if they so happen to lose one. Anyway, I have done some more research on other animals that have the ability to regenerate. Among those animals includes humans, earthworms and planarians. Humans can regenerate skin and bone tissue and even part of a liver! But humans cannot regenerate body parts like a finger (liver is the only exception). Earthworms have the ability to grow an entire body as long as the front part of the organism is present. And lizards can grow back tails with the goal of deceiving its enemies. Fiddler crabs can regenerate their big claw during the molting period. This is a very slow process that only happens two to three times a year. During this process, the small claw will grow and be the big claw and the once big claw will re-grow and be the small one.

    http://www.daviddarling.info/encyclopedia/R/regeneration.html
    http://www.absoluteastronomy.com/topics/Fiddler_crab

  • Carl

    I think that this is a very interesting post. In my research, I found that there are other animals that can be deceitful. For example, the western-banded gecko can shed and re-grow its tail. A test was done at the University of Arizona in which 30 geckos were placed with their natural predator, the spotted night snake. Out of all of the lizards, nineteen were able to get away by shedding their tails. Later, the scientists used the same species of lizard and same species of snake in another experiment; this time the lizards had no tail. Having no tool to aid their escape, all of the geckos were caught by the snakes. This proves that being able to shed a body part, or being deceitful, is a great way to escape from a predator.

    http://www.newscientist.com/article/mg12517024.000-the-throwaway-tail-lizards-often-give-up-their-tails-to-escape-from-predators-how-and-when-they-do-so-depends-on-their-evolutionary-history-and-the-complex-relationship-between-benefits-and-costs.html

  • http://scionlineproject.blogspot.com Michael S

    Fiddler crabs (Kindom:Animalia, Phylum:Arthropoda) are very interesting animals. Their scientific name is Uca rapax. They live in salt marshes a lot the Gulf of Mexico and South America.
    Fiddler crabs eat decaying plant and animal matter as well as fungus and bacteria.
    The fiddler crab has a very creative and fun way to attract mates, it waves its big claw in a way that it looks like it is fiddling. Then it waits for a female to come by, then it bangs its large claw on the ground to tell the female he is available. If the female is interested and there is no competition then she will move into the male crabs burrow and they will mate.
    Male fiddler crabs have a large claw (as stated in the article) and a smaller claw. Males only use the small claw to feed, therefore it makes it very difficult to get food. Their larger claw is used in competition for mates. Male fiddler crabs fight until one submits, looses its claw, or dies. If the claw happens to fall off then the male can regrow its claw. The regrown claw is larger then the last one. [ http://www.tpwd.state.tx.us/huntwild/wild/species/fiddler/ ]
    [ http://www.fiddlercrab.info/ ]
    And to answer a few questions, yes these crabs can regrow their claws numerous times, this leads them to having bigger and bigger claws. This can also be useful to humans because if we figure out how the regrowth of claws works in claws then we can attempt to make humans regrown limbs.

  • Justin

    Good post Collin! Fiddler crabs are small semi terrestrial animals. These crabs have one small claw in which they use to pick up their food which is mostly bacteria and algae. They have a large claw that contrary to popular belief is not used for self defense but rather for finding a mate as well as discouraging their rivals. To answer your question about if they can lose their claw multiple times the answer is yes. Fiddler crabs actually are supposed to molt twice a year. During this period their claws are soft but they hide in a burrow for protection that can be up to two feet deep.

    http://www.chesapeakebay.net/fiddler_crab.htm

  • victor

    Fun post. When I thought of animals that lie animals that camuflage instantly came up to mind. Animals that camuflage are usually insects that do not have strong defensive mechanisms, so their best bet at survival is to hide. Camuflage is about triking your preditor or prey into thinking your something that your not. One insect I found that was paticularly good at camuflaging was a moth. As moths don’t contain shells or venom they deeply relie on their camuflage. Here are different types of moths and other cool insects that camuflage http://www.cals.ncsu.edu/course/ent425/tutorial/Ecology/camo/index.htm
    Can you find any animals that are not insects that camuflage?

  • phoenixia

    There are many deceptions in the animal kingdom, and one of them is mimicry.
    Mimicry is the similarities between species , unlike camouflage that refers to the resemblance of an animal to an inanimate objects. There are three types:
    Batesian Mimicry- named after British scientist Henry Walter Bates who studied this in butterflies. This mimicry occurs when two species look the same , but only one species has the defense such as spines or poison. Since one species is unpleasant, the predator would associate the species that looks like the unpleasant one with being unpleasant.

    Mullerian Mimicry- is named after German zoologist who worked in the Amazon 3 decades after Bates . This form refers to when two unpleasant species mimic each other, so when the predator keeps eating the frogs before it realizes they are unpleasant, the species would not be impacted as much because the impact is spread over several species.

    Self mimicry- refers to when a animal mimics a body part on another body part, for example some moths have “eyespots” on their wings. This help these animals escape or increase survival by helping them not get a severe injury.
    http://rainforests.mongabay.com/0306.htm

  • Anna

    This is a great article showing how animals deceive others especially when facing their predators. I have learned while researching if animals lie, that “lying” is a sign of intelligence. Thus the more advanced and intelligent the animal, the more likely it will use this method to get what it wants. The act of deceiving another animal to get what it may want or need is an intelligent way of being successful. The Peacock is another animal that uses deception to get what it wants. When wanting to attract mates, it quickly displays its large colorful feather trains. The Peacock uses it feathers when performing. Females choose who they will mate with by the beauty and size of male’s plumage. Peacocks use this deception method to make themselves seem much larger, and more appealing than they really are, when not trying to attract females. It is known that Peacock’s feathers are more than 60% larger than the total length of its body.

    This is where I found my information:

    http://animals.nationalgeographic.com/animals/birds/peacock.html

    http://www.healthdiaries.com/animals-lie.htm

    http://www.rochester.edu/news/show.php?id=1421

  • Sam

    After reading this post I decided to look up more deceptive animals that use senses and parts of their body to intimidate their predator or deceive them at least. I cam across a certain intelligent primate called the Vervet Monkey. The vervet uses a an emergency call that distracts it’s predator and gives the monkey time to escape and warn his fellow monkeys that their is a predator near. The vervet monkey’s predators include leopards, eagles, baboons, and pythons. These monkeys recognize each call as a dangerous one because their memory is so strong that they know the calls for certain predators and how to escape them. There was also a study about these deceiving animals that these monkeys are more likely to make these calls when they have a member of their family nearby because they are protective and want to keep them away from danger. To find more information on these bluffing animals you can visit this website:
    http://www.bio.davidson.edu/people/vecase/behavior/Spring2009/Foley/index.html

  • Chris Muro

    The fiddler crab is a very unique animal. The fiddler crab is very smart and how it lies to its predator that it is as strong as the other crab. The fiddler crab when looses its claw and grows back a new one that isn’t as strong and is a little smaller then usual.
    http://www.telegraph.co.uk/earth/wildlife/3439087/Crabs-use-their-claws-to-lie-about-fighting-ability.html
    An ecologist from Australia, Dr. Lailvaux studies fiddler crabs. He stated that the crabs are very smart and when they lose a claw it grows back weaker because of the size of the claw, but they still fight and can attract other females.

  • Alex

    The male “Uca papax” (most commonly known as the fiddler crab) is known for the color of their claws and how massive it is. In the study shown on this link, the female crab was given the male claw- and you can see the results of the claw on their feeding, mating and other survival tactics.
    http://www.springerlink.com/content/p437311815113171/

  • Jack

    On the topic of dishonesty, there is alot we still can’t tell. Many people have said that lying is a learned trait, and that parents teach lying to their children. [ http://writeeditrepeat.blogspot.com/2009/10/parenting-by-lying-where-do-you-draw.html ](this is just one of many sites that give simmilar information) If this is true, it is interesting to see some “lying” in the animal world other than in humans, as it shows that even if lying is a learned trait, it may have been developed through evolution. I have found an article about animals that lie, but it seems that even when animals lie, they only do it to live. [ http://cristinaenglish.blogspot.com/2009/03/lying-animals.html ]
    There are some birds who cry hawk in order to get others to hide so they get more food for themselves (I wonder if the other birds will believe him/her when there actually is a hawk…) It is possible that camouflage in itself is evolutionary lying. Is there a common source to where all this lying developed?

  • Carl

    To add on to what Michael S said, if the male’s claw keeps on getting larger, it will most likely be able to attract more females because this ornament is used in the mating process. Different organisms have different mating processes. With most animals, the males have specific ornaments in which they use to attract females. In the case of collared flycatcher birds, the males have a white spot on their forehead. The larger the spot, the more likely the bird will mate.

    http://missbakersbiologyclasswiki.wikispaces.com/Carl

  • Rohit

    This was a very interesting post. I never knew that fiddler crabs were dishonest. It’s also amazing how fiddler crabs produce another claw after losing it. The new claw looks similar but it is not the same. Dr. Lailvaux and scientists from Australian National University measured the size of the major claw in male fiddler crabs, and two elements of fighting. They found out that the size of an original claw accurately reflects its strength and the crab’s ability to avoid being pulled out of its burrow. This is not the same for a regenerated claw. This is the site I found the study on.

    http://www.terradaily.com/reports/Fiddler_Crabs_Reveal_Honesty_Is_Not_Always_The_Best_Policy_999.html

  • Charlot

    I never knew that fiddler crabs could grow back claws after losing one. What really interests me is that every time they re-grow a claw, it gets bigger and bigger but has less physical use and is more for show. I was also interested in how Mike mentioned the idea of limb regrowth in humans.

    I found an article about the possibility of humans regenerating limbs. The study shows that salamanders can regrow limbs, but most other animals and humans can’t. Scientists did an experiment on a chick that was still in its embryo. They took off a part of one of the wings and activated the Wnt signaling system. This is a system that plays a role in cancer cell spreading. The chick grew back its wing. This method could be useful in the future for human limb regrowth, but there are some serious consequences. If the Wnt signaling stays on for too long, it can cause cancer.

    http://www.scienceagogo.com/news/20061019233435data_trunc_sys.shtml

  • CHRISTIAN

    great post collin. fiddler crabs are really cool, their claws and ability to regenerate is awsome. i did some research on the regeneration process of a starfish, and found that, when a starfish loses an arm or leg the regeneration process is just a structure rebuilding every cell.
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1692227/
    here is a video of starfish regeneration.
    http://www.youtube.com/watch?v=f7cXeWxxfD4

  • Michael L.

    This is a great thing for evolvement in the crab because they say that it is a learned trait. Since the claw keeps growing and getting larger they have a better chance of producing offspring. Therefore, they have chances to always reproduce. I also found out something interesting, because the Vervet Monkey has this emergency call that it uses to distract its predator. Its main predators are Leopards and Eagles. Vervet Monkeys later have an amazing memory and then they know how to escape its predator. There have also been studies about how they do their call to bring nearby family and monkeys. They do this to be protected.

    http://www.outtoafrica.nl/animals/engvervetmonkey.html?zenden=2&subsoort_id=1&bestemming_id=1

  • Justin

    I find it very interresting that fiddler crabs can easily regenerate limbs.Regeneration is the process off growing a limb after it is lost.No mammals are known to regenerate limbs but salamanders are one of the few organisms with this ability.Salmanders when approached by their prey make their tail fall off,this distracts the predator for long enough to allow the salamander to get away.
    http://www.sandiegozoo.org/animalbytes/t-salamander.html

  • Alec

    Many animals have qualities that appear to be intimidating, however, most of these animals are bluffing. For example, bluffing occurs when two crayfish fight over a mate. The larger claw that a crayfish has is not it’s most important weapon. In fact, the other claw does more damage. However, there is an evolutionary advantage to possessing the big claw. If two crayfish are ready to fight, and if one frayfish as a significantly larger claw than the other, then the crayfish with the smaller claw will flea. The anglerfish is another animal that bluffs. On the tip of the anglerfish’s snout a rod that has a glowing end which acts as fish bait. The glowing tip looks like a worm, or even a clump of alge to nearby fish. The nearby fish think it is a tasty snack, when in fact the anglerfish jiggles the bait in front of it’s so lure the fish as close as possible. Then, right when the smaller fish takes a bite at it’s “snack”…SNAP, the anglerfish has dinner!

    the information from the post was found on: http://www.livescience.com/animals/070726_crayfish_bluffing.html
    http://findarticles.com/p/articles/mi_qa4128/is_200610/ai_n17194550/

  • bobby

    this is really cool, i never wouldve though that animals could be this smart. i found that a horned lizard when its being attacked takes its horns and increases its sinus presssure so that its eyes pop out and squirt blood at its predator. here are a bunch of differnt defense mechanisms.
    http://scienceray.com/biology/zoology/strange-defense-mechanism-of-animals/

  • Michael L.

    Nice post Collin! When I read this post it reminded me of something similar that humans do. Some people will take steroids to enhance the size of their muscles to seem more intimidating to others and also to attract a mate. Fiddler crabs are able to regenerate their big claw after molting a few times. The reason they are bigger and lighter than the original is to be more successful for reproduction. If they seem like a good mate they will reproduce and pass on their genes. So through natural selection crabs with the “cheap” claw gene began to appear more in the species.

    http://www.anu.edu.au/BoZo/backwell3/Fiddler%20Crabs.htm

  • Joseph

    This is a really cool post. Fiddler crabs are interesting animals for many reasons. As the male grows to maturity, the relative weight of its large claw, or cheliped, changes from 2% to 65% of its total body weight. They are brown in color, with the front of the shell and eyestalks ranging from blue to turquoise. The large claw of the male is usually yellowish orange to yellowish white, and its walking legs are dark and banded. Here is more information on the fiddler crab: http://www.dnr.sc.gov/marine/mrri/acechar/specgal/fiddler.htm
    There are many other animals that lie. One of them is the anglerfish. Dangling from a spine on the tip of its snout is a built-in fishing lure. When the angler fish is hungry, it searches around for prey and dangles around its “bait” so it looks like a fish swimming. When the anglerfish’s prey comes by to get the “bait”, it eats it.
    Besides the dangler fish, there are animals that fake other animals in courtship rituals. For example a certain type of male firefly sends out a certain signal when it wants to mate. A female firefly then mimics this signal. When the male comes over to her because he thinks that she wants to mate, she kills him and eats him. There are many more examples. For more, got to: http://www.britannica.com/bps/additionalcontent/18/22604917/DO-ANIMALS-LIE

  • Cheyennne G.

    I think this is a great post! very interesting and thought out. I never thought about this. Well I sort of did because my dog isn’t always honest but anyway great job on the post.

  • Josh

    This is a very interesting post, but there is more than dishomesty there are bombs in the animal knigdom. A new annelid species was found that projects green bombs to distract predators so it can get away. This annelid is called, Swima bombiviridis or swimming green bomb.

    http://news.nationalgeographic.com/news/2009/08/photogalleries/worms-glowing-bombs-green-pictures/

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