A team of Australian ecologists has discovered that some male fiddler crabs “lie” about their fighting ability by growing claws that look strong and powerful but are in fact weak and puny. Published this week in the British Ecological Society's journal Functional Ecology, the study is the first direct evidence that crabs “bluff” about their fighting ability.
The signals animals send each other about their fighting prowess - and the honesty of these signals - is a long-standing problem in evolutionary biology. Despite their size - they are just two centimetres across - fiddler crabs are ideal for studying dishonesty in signalling. This is because males have one claw that is massively enlarged (which they use to attract females or fight rival males) and if they lose this claw during fights they can grow a replacement. In most species the new claw is identical to the lost one, but some species “cheat” by growing a new claw that looks like the original but is cheaper to produce because it is lighter and toothless.
According to lead author of the study, Dr Simon Lailvaux of the University of New South Wales: “What’s really interesting about these 'cheap' claws is that other males can’t tell them apart from the regular claws. Males size each other up before fights, and displaying the big claw is a very important part of this process.”
Dr Lailvaux and colleagues from the Australian National University measured the size of the major claw in male fiddler crabs, and two elements of fighting ability - claw strength and ability to resist being pulled from a tunnel. They found that while the size of an original claw accurately reflects its strength and the crab's ability to avoid being pulled out of its burrow, this relationship does not hold true for a regenerated claw.
“This means that while males can gain an idea of the performance abilities of males with original claws from the size of those major claws, regenerated claws don’t reveal any information on performance capacities. Males with regenerated claws can 'bluff' their fighting ability, like bluffing in a poker game. They’re not good fighters, but the deceptive appearance of their claw allows them to convince other males that it’s not worth picking a fight with them. The only time it doesn’t work is when regenerated males hold territories, which means they can’t go around choosing their opponents - they have to fight everyone who challenges them, and eventually someone will come along and expose their bluff.” Lailvaux explains.
The study is important because it helps shed light on an issue - dishonesty - that is by definition hard to study. “One of the reasons we don’t know a huge amount about dishonesty is because it’s tough to pick up on it. Dishonest signals are designed to be difficult to detect, so to have a system like fiddler crabs where we’re able to do experiments and test hypotheses about dishonesty is pretty cool,” he says.
The results also have important implications for individual reproductive success and survival, as understanding the mechanisms and consequences of dishonesty is essential to uncovering the full story of how these and other animals live, die and reproduce.
According to Lailvaux: “By studying exactly how animals fight, and 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. Honest signalling is important for several reasons, primarily because it’s important that fights don’t always escalate into bloody violence. Fighting can be costly in terms of time and energy, and it’s in an individual’s best interest to avoid risking being injured in a fight, so one of the reasons why we think honest signalling has evolved is because animals need to have a diplomatic option for settling disputes, as opposed to duking it out with every male that comes along. If there’s a way for individuals to assess beforehand which males they are likely to lose to in a fight and which ones they are able to beat, then that allows them to plan accordingly.”
Fiddler crabs live in mangrove swamps and mudflats. There are around 100 species worldwide. Despite their propensity for dishonesty, the name fiddler crab comes from the fact that while waving their big claw to attract females they look like they are playing the violin.
Simon P Lailvaux, Leeann T Reaney and Patricia R Y Backwell (2008). Dishonesty signalling of fighting ability and multiple performance traits in the fiddler crab Uca mjoebergi. Functional Ecology, doi: 10.1111/j.1365-2435.2008.01501.x, is published online on 12 November 2008.
Becky Allen | alfa
How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy