Honest Signalling in Koalas

Dr Bill Ellis is a postdoctoral researcher in the lab, who spends much of his time in the field tracking and studying koalas (and other cool animals).

In a recent project, Bill and colleagues (from Australia and the University of Vienna) learned that male koalas - which make loud, grunting bellows - have a particular vocal anatomy that means their call can give others a non-visual indication of the caller's body size.

This is the first time that a permanently-descended larynx has been found in a marsupial.

Pretty cool.

Though Robbie and the rest of us in the lab weren't part of this research, we're proud of Bill's awesome work, and thought you might like to read about it! You can find out more about the project here, on the Koala Ecology Group website or more about animal signalling here.

Animal Signalling

We're giving signals whether we know it or not. All the time - and without saying a word - we show others that we're bored or interested or infatuated or annoyed ... And this ability certainly isn't unique to humans.

Signalling is pretty much everywhere in the animal kingdom.

We know that some organisms use displays or calls or body structures to attract mates ... or ward off intruders ... or show how wonderfully strong and appealing they are. (Hmmm ... can you think of any examples?)

But what scientists are starting to figure out is that not all these signals are - shall we say - honest. Sometimes appearances aren't the same as reality. And there are times when it pays to show what you might be, rather than what you actually are. We're studying dishonesty in signalling in a number of different research systems, including crabs (who signal strength via their claws) and soccer players (who signal fouls via dives).

photo by Skye Cameron

You can read more about our signalling work here:
Cheating pays off for females but not males
How humans differ from crabs

Or here:
Walter G, Van Uietregt V, & Wilson RS. 2011. Social control of unreliable signals of strength in males but not females of the crayfish Cherax destructor. Journal of Experimental Biology. 214: 3294-3299.

Wilson RS & Angilletta MJ. In press. Dishonest signals of strength. In Ed. D. J. Irschick, M. Briffa, and J. Podos. Animal Signalling: a Functional Perspective. Ralph Wiley Press.

Wilson RS, Condon CH, David G, FitzGibbon SI, Niehaus AC & Pratt K. 2010. Females prefer athletes, males fear the disadvantaged: different signals used in female choice and male competition have varied consequences. Proceedings of the Royal Society of London Series B 277: 1923-1928. 
 
Wilson RS, James RS, Bywater C & Seebacher F. 2009. Costs and benefits of increased weapon size differ between sexes of the slender crayfish, Cherax dispar. Journal of Experimental Biology 212:853-858.

Bywater C, Angilletta MJ and Wilson RS. 2008. Weapon size is a reliable predictor of weapon strength and social dominance in females of the slender crayfish. Functional Ecology. 22:311-316.

Seebacher F & Wilson RS. 2007. Individual recognition in crayfish (Cherax dispar): the roles of strength and experience in deciding aggressive encounters. Biology Letters 3:471-474. 
 
Wilson RS, Angilletta MJ, James RS, Navas C & Seebacher F. 2007. Dishonest signals of strength in male slender crayfish (Cherax dispar) during agonistic interactions. The American Naturalist. 170:284-291

Cheating Pays Off for Females But Not Males

In the social circles of crustaceans, the claw means everything. Larger claws can be used to signal dominance, staving off unnecessary battles between poorly-matched opponents. However, if two similarly-sized individuals fight it out - it's usually the one with the stronger claw that wins.

Fighting fiddler crabs - photo by Skye Cameron

Unlike humans, where opponents can assess strength visually (e.g. bicep size), crustacean muscle is contained within a hard exoskeleton. This means that crustaceans can't determine each others' strength without testing it in combat, and it opens the possibility for cheating. Cheating could benefit individuals by gaining them dominance without having to fight; meaning access to better quality food, enhanced mating opportunities, and safer shelters - all without risk of bodily harm in combat or the high metabolic costs associated with maintaining strong claw muscles.

And cheating may be as easy as growing a large, wimpy claw.

By and large, animals are thought to signal their value (i.e. strength, power, dominance) honestly. But Dr. Robbie Wilson of the University of Queensland has found that many crustacean species actually cheat - producing large but weak claws that fool potential competitors.

These are exciting findings, because they show that cheating is likely to evolve under particular circumstances.

As part of his honours research in Dr. Wilson's lab, Gregory Walter found that female crayfish, Cherax destructor, are more likely to benefit from cheating compared with males. In his experiments, he measured claw sizes, body sizes, and claw force for each crayfish, and then observed which crayfish won in competitive, same-sex bouts - and, importantly, whether dominance was gained by signalling or battling.

Cherax destructor - photo by Gregory Walter

"We found that having large, wimpy claws was prevalent among both males and females," explains Dr. Wilson. "But only females gained dominance by cheating."

It turns out that male C. destructor tended to fight more often than females, so dominance among males was acquired via claw strength - an unfakeable trait. On the other hand, dominance among female C. destructor was most often determined via signalling alone, leaving claw strength untested and rewarding females with large, but weak, claws.

"In fact, females were pretty bad at judging each others' potential strength [based on claw size]," Dr. Wilson continues. "Giving sub-standard females the chance to be dominant."

This work has just been published as:
Walter G, Van Uietregt V, & Wilson RS. 2011. Social control of unreliable signals of strength in males but not females of the crayfish Cherax destructor. Journal of Experimental Biology. 214: 3294-3299.

You can read more about Dr. Wilson's research on honest signalling here. 
Written by Dr. Amanda Niehaus

Sabbatical is Not Just One Big Holiday ...

Robbie's currently on sabbatical - or long study leave. But what is it? And what exactly is Robbie meant to be accomplishing on all these trips to the US and Europe and Sydney and Groote Eylandt?

Well, according to Wikipedia a sabbatical is:

'a ceasing [of] work, or hiatus.' 

But it also says - hidden a paragraph or two later - that in modern times a sabbatical is:

'any extended absence in the career of someone in order to achieve something.'

Uh oh. So there are expectations.

At UQ, a sabbatical is granted every 3 to 5 years - and gives academics 6 months off from administrative and teaching duties. There is an expectation that the academic will use this time wisely - to collaborate with researchers overseas, or undertake extended field trips, or write a book, or punch out half a dozen publications or so. Basically, it's time to catch up on all those things that an academic is supposed to be doing (in between teaching and supervising and sitting on committees).

The academic-on-sabbatical doesn't actually have to leave home - but getting out of town does make it easier to leave office stresses behind and focus.

On his sabbatical, Robbie will attend two overseas conferences; collaborate with researchers in Sydney and France and Phoenix; finish up those 20 or so papers that currently hang in various states of completion/submission/revision; begin writing a book on maximising soccer performance; make two jaunts field trips to Groote Eylandt; and various other duties that will enhance his career and make his life easier when he returns to full-on duties in February.

So there you have it: what a sabbatical is, where you can still get one, and what you might like to do while you're on it. Not bad, hey?