What Determines Gecko Fighting Performance | An Honours Project by Rebecca Wheatley

This is Rebecca. She just submitted her Honours thesis, and is probably chilling with a vodka lemonade on a beach somewhere. | Or else she's wishing she was. |

A couple months ago, I asked Bec to describe her thesis - and to show me the experiments she had running. Here's what she said:

My research is using Asian house geckos as a model to answer questions about how morphology, performance, metabolic rate and personality interact to affect fighting ability in animals.

Gecko housing project

Rebecca's work is exciting because few studies have evaluated how morphology (or body size | shape), physiology, and personality work together to determine animal performance.

And can animals really have personalities? Of course, but not like you and I do. In the non-human world, personality can refer to repeatable differences in behaviour among individuals. For example, some individuals consistently tend to be shy, and others tend to be bold. Boldness | shyness is important for animals, as it can determine the likelihood of obtaining food or mates, or getting captured by predators.

When I caught up with Rebecca, she was measuring geckos' metabolism in purpose-designed jars, which were hooked up to specialised equipment that measures oxygen consumption. Oxygen consumption is one way that scientists assess metabolic rate in animals in the lab.

collecting data on gecko metabolism

Rebecca was also video recording interactions between randomised pairs of geckos. Asian house geckos are aggressive little lizards, and will sort out dominance via displays of their open mouths, biting, and | or chasing. In her thesis, Rebecca looked at which animals were likely to be dominant, and whether that depended on their metabolism, morphology, and | or personality. 

collecting data on gecko fighting

And what did she find? The oversimplified version is that bite force, body mass, and running speed were most important in determining gecko dominance. Big, fast, hard-biting geckos were likely to be winners. The surprising thing was that metabolism and boldness didn't seem related to fighting performance.

There's a lot more to Rebecca's research: she used all the information she collected on morphology | physiology | behaviour to test important ecological theories about how individuals should interact (known as game theories). But we'll talk more about that another time - we don't want to give away everything just yet.

Thank you Rebecca, for taking the time to share your honours work with us, and for being such a wonderful labmate!

written and photographed by Amanda Niehaus, PhD

Welcome to Our Newest PhD Students

The lab is getting bigger! Andrew Hunter {Chopper} and Ami Fadhillah Amir have just joined the lab to do their PhDs - Chopper on performance and Ami on conservation. Ami acquired a prestigious Malaysian scholarship for her work, so we don't know for sure if the following is applicable for her ... but for Chopper, at least, post-doc Sean Fitzgibbon put together a financial plan for his upcoming years of servitude:

"Chop, I have just looked at the conditions of your award and spoken with your accountant.

We offer the following:
Stipend $23,728 per annum (Tax-free) = $461/wk

Committed expenditure:
Mortgage $380/wk remainder $81
Utilities $28/wk remainder $53
Football subs $17/wk remainder $36
Groceries $23/wk remainder $13
Home brew $8/wk remainder $5

We suggest that you set-up a trust savings account to invest your weekly surplus income of $5. Based on my calculations, after your PhD you should be able to live off your savings (and interest - based conservatively on 6.2%) for approx. 2.1 days. This should really take the heat off when you are searching for a job post-hand-in

Welcome to the familia! Let me know if we can be of further assistance*." - S.F.

*this post is not meant to replace real financial planning and new PhD students should always consult a bona fide accountant for advice on saving vs. spending their income. If they can afford one.

Fieldwork, Groote Eylandt, NT

It was only a week ago we got back from Groote Eylandt. What a special place. Wild, and raw, and special. An island of contrasts, between a traditional culture and a modern mining industry. An island with a lot of crocodiles.

the GEMCO manganese mine

It was my first trip up, and Nelle came along. We met the Rangers and friends and family and Gavin and Kerry and the rest of the team and Alex-from-Stanford. We drank tea on the deck at the Ranger station, and packed up everything {but petrol} for a quoll-catching venture to the east side of the island. {Former labmate} Billy was appointed Ranger Coordinator. We learned our first Anindilyakwan words. We entertained Nelle, and learned the value of ABC for Kids downloads {and PhD students}.

On the deck with Jennifer and her niece; with Chopper; with MacBook Pro

We drove east to Umbakumba then headed into the bush on sandy tracks. We set up tents on top of a berm, feeling {relatively} safe from water-borne crocs and collected firewood from the beach. We watched a heavy moon pull itself up into the sky.

Picnic Beach, Groote Eylandt

Under Jaime's guidance, we set out traps for quolls, hoping to catch at least a few to obtain measurements and hair samples.

Jaime and Eddie set out, bait, and mark quoll traps

We caught 4. Plus a few bandicoots. It was good enough for Jaime to get her samples, and good enough for me - these were the first wild quolls I'd seen.

A quoll curled up in its very own, custom-made pillowcase

We were almost as successful catching fish ... the ocean here teems with them {apparently} but we didn't have much luck. Three fish only made it into our bellies.

That's ok. We had plenty of patience ... 

and potatoes. 

fishing for dinner

- written by Amanda Niehaus

Groote Eylandt, August 2012

Leaving Darwin, the propellers outside hummed loudly (reassuringly). We pressed our noses to the windows, looked out on the wild top coast of Australia. The fires lit by thousands of years of tradition. And then, we were there. Over the mines, into the red dirt.

Groote Eylandt.

Crabs will fake it to avoid a fight

Crabs will fake it to avoid a fight, research finds

Dr Robbie Wilson, Head of the Performance Lab at UQ, where this study was conducted, said the research identified more than just some crabby behaviour.

“This study is important because it reveals the general principles behind how liars and cheats are controlled and encouraged in nature.

“Whether it's a soccer player diving to fool a referee or a crab trying to intimidate a rival with weak claws, our lab has shown that individuals cheat more when their deception is likely to go undetected,” Dr Wilson said.

Ms Candice Bywater who is finishing her PhD on fiddler crabs, said that she found that more males bluff their way through fights when they are less likely to get caught.

photo by D. Hancox

“When there are lots of crabs living in one area, there is lots of competition for resources like females and food. High competition means there is a greater chance of males having to fight each other to win resources compared to when there are not many crabs about. Those crabs might not have to fight at all,” Ms Bywater said.

“Crabs that have strong claws will generally win fights. Producing large and strong claws is important to their survival.

“Where crabs are likely to have to fight a lot, the crabs are producing large, strong, reliable claws. We found that when there are not many other male crabs in a population (low competition), males produce large but relatively weak claws (unreliable), as they don't have to fight as often and ultimately because can get away with it."

In nature, signals may be behavioural, as in growling or posturing, but are often structural, including the antlers of a deer, and the enlarged fore-claw of many crustaceans.

A male that overstates his quality could improve his ability to gain food or mates, but surprisingly, most signals are honest reflections of a male's prowess.

Media contact: Dr Robbie Wilson, School of Biological Sciences, E: r.wilson@uq.edu.au, mobile: 0458 204 962; Performance Lab: http://www.wilsonperformancelab.com/ 

Bywater, C & Wilson RS. 2012. Is honesty the best policy? Testing signal reliability in fiddler crabs when receiver-dependent costs are high. Functional Ecology.

David GK, Condon CK, Bywater CL, Ortiz-Barrientos D & Wilson RS. 2011. Receivers limit the prevalence of deception in humans: Evidence from diving behaviour in humans. PLoS ONE 6(10): e26017 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0026017

Written by UQ Media

How to fight dirty

If you're a crayfish, your best bet is probably to grow an intimidatingly-large claw ...

but pack the muscle (i.e. punch) into the other claw.

Many animals - like crayfish - signal their fighting prowess by displaying specialized limbs, musculature, or weaponry to others. In signaling, bigger is often better; but in a fight, rivals could gain advantage by concealing their real strength in less conspicuous limbs.  

Cryptic asymmetry occurs when differences in limb strength are unrelated to differences in limb size, and was previously considered only in primates; however, we found asymmetric strength in males of the slender crayfish, which use their claws in display and combat. 

In a paper just published in Biology Letters, Robbie and collaborator Mike Angilletta suggest that asymmetric strength could be used to confuse rivals and influence the outcome of fights.

(look over here ... look over here ... )

 WHAM.

Big News at the Moment - Feb 2012

1. Robbie got his 69th publication, and for some reason thought that was funny.

2. Candice returned from the US, jet-lagged and culture-shocked. We've missed her.

3. Billy's still ... somewhere?

4. Jaime's officially started her PhD, and taken up the last desk in the Fun Zone.

5. Another of Candice's PhD papers just got accepted for publication! This one's:
Bywater, C & Wilson RS. 2012. Is honesty the best policy? Testing signal reliability in fiddler crabs when receiver-dependent costs are high. Functional Ecology (in press Feb 2012)

6.  Robbie decided it was time to get married. To me.

And that's February, 2012!

The Scent of a Predator (Well, Kind of)

The following article is adapted from a talk presented by Jaime Heiniger at SICB 2012, along with coauthors Billy Van Uitregt and Robbie Wilson. The original talk was called: "Fine tuning anti-predator responses: are the costs of inducible predator defences proportional to the magnitude of the responses?"

***

For amphibians, it's a mad, mad world. And - importantly - an unpredictable one. Natal pools might contain predators, or not; competitors, or not; food, or not; and conditions can change every day. As a result of all this unpredictability, many amphibians can alter their appearance and behaviour in ways that increase their likelihood of survival. But these defensive strategies usually come at a cost - slower growth, higher metabolic requirements, and smaller size at maturation are just a few common outcomes.

toadlets in the lab

To maximise the benefits and minimise the costs associated with predator defense, it's predicted that the magnitude of the defensive response should reflect the magnitude of the threat. Thus, more threat = more phenotypic change; and less threat = less phenotypic change. This is known as the threat-sensitive predator avoidance hypothesis (TSPAH), and although it's known that prey can fine-tune their responses to the degree of predation risk, it's unclear if the magnitude of threat-sensitive defensive responses relate to their associated costs.

{Jaime} tested this idea by examining the effects of increases in perceived predation risk on the expression of defences and their associated costs in larvae of the toad, Bufo marinus. She reared tadpoles in varying concentrations of predation cue* and quantified their growth, morphology and development, as well as metamorphic size, locomotor performance and oxygen consumption.

*for those curious, predation cue is actually water from around deceased tadpoles. Tadpoles are sensitive to the smell of their dead mates. (Aren't we all?)

taddies in the lab

{Jaime} found that tadpoles responded to increases in perceived predation risk by gradually decreasing their activity.

As a consequence of their more-sedentary lifestyle, individuals metamorphosed later, smaller and with reduced endurance. Toads that emerged from the different treatments didn't vary in maximum jumping distance but those from 'high predation' treatments metamorphosed with longer relative hind limbs - meaning they could jump farther for their body size.

jaime's metamorph habitats

 These are interesting results, because they show that
a) toads produce defenses that are proportional to the perceived threat
b) defensive behaviour is costly
c) the costs are in proportion to the amount of defense
d) but phenotypes produced in response to predation threat may aid the individual.

Cool stuff, Jaime!

Why Be Fake? Because Honesty is Too Expensive ...

In earlier posts, we've talked about the life of a crab ... and about the predisposition for some crabs to fake how strong they are. At SICB in January, Candice presented a talk detailing why exactly it pays to be weak.

image by Dan Hancox

Here's my recap on Candice's talk ...
Crustaceans are violent types, posturing and fighting for territories, mating partners, and resources. Because claws are such excellent weapons, fights are often decided by the individuals merely checking each others' claws out. Bigger claws = dominance. This ameliorates the risks associated with claw-battle, while still deciding dominance.

But Candice has found that the size of the claw is not always indicative of its strength - namely, some individuals are fakers. You see, claw muscles - which are used to clamp and tear in a fight situation - are hidden inside the chitinous claw. So a big-clawed crustacean might just lack big muscles underneath, meaning it's more likely to lose if the interaction escalates into a fight.

So why wouldn't a crustacean just grow the muscle? This is what Candice wondered. She noticed that crabs with re-generated claws tended to have wimpy claws, relative to their claw size. So, she measured the energy needed to maintain claw muscles in fiddler crabs with strong, original claws as well as crabs with weak, regenerated claws.

 

Candice believes that dishonesty in fiddler crabs is related to metabolic costs - namely, how much energy is required to keep that muscle active. Crabs with strong, original claws spent ~22% of their metabolic energy budget on their claw muscle - pretty close to the amount of metabolic energy humans use to support our large glucose-hungry brains.

In contrast, crabs with weak, re-generated claws used only ~12% of their daily energy on claw muscle.

That constitutes a massive energetic savings for fakers, unless they get caught ...

CB in DC

At this precise moment, Candice is working at the Natural History Museum in Washington, D.C. - measuring crustacean claws as part of a study for her PhD.

Or, she might be sleeping. (I can never get those time-differences right ... )

At any rate, this is her lovely little brownstone ...

She's even famous now, in a "The Lost Symbol" kind of way, toiling away in the crustacean collections in Pod 5* at the Museum Support Centre (MSC), a high-security warehouse in the sketchy part of town.

*The same section of the warehouse featured in Dan Brown's book ... in case you haven't read it yet.
 

And how does Candice spend her days in DC? She's on the bus at 7:30, heading to the Natural History Museum in downtown DC, where she catches the shuttle to the warehouse facility where the crustacean collections are housed.

In to her little lab in the wet collections rooms by 8:30, she starts taking photos of crab claws and measuring the sizes of the shell and legs - for different specimens and different species. It sounds like quick work, but given she has to take 3 measurements of each crab leg (and each crab has 8 measurable legs), she may just be there ... all year.

Not really. But I'm sure that's how she feels sometimes. 10-15 minutes per crab x a warehouse full of crabs = significant porters needed at the end of the day.

Candice measures claws on her own, but has lunch with the other 10-15 researchers who work at the warehouse measuring, cataloging and sorting other types of invertebrates. They all chat and sometimes have science talks, so it's been a great way to meet everyone else.

Then it's back home again, to forget about claws for 12 hours or so.

And why is she doing all this? Candice is looking for tradeoffs between claw size and other morphology among different crustacean species - compensatory mechanisms (like we just learned about with geckoes). We'll talk more about the science after she gets back.

(all the pictures in this post were provided by Candice. Thanks!)

Trade-offs in Gecko Design

Sounds glam, right? Gecko design?

At the 2012 SICB in Charleston, Skye presented research that shows how traits that improve bite force in geckos have negative impacts on the gecko's sprint speed. Meaning that males who are better fighters might also be less adept at escaping predators ...

Costly design indeed.

Let's learn more by having a look at Skye's abstract, with {comments in brackets from me}.

Trade-offs and compensatory traits: bite force and sprint speed pose conflicting demands on the design of male geckos (Hemidactylus frenatus)

by Skye Cameron, Melissa Wynn and Robbie Wilson

The evolution of exaggerated ornaments and armaments is driven by the benefits accrued to reproductive success and by the costs imposed on viability. {This means that} when traits are required to perform multiple functions that are important to both reproduction and viability, trade-offs can result in a compromised phenotype.

{Imagine, for example, a species of bird in which females are more likely to mate with males that have larger tails; but males with larger tails are more likely to be captured by predators. Both reproductive potential and survival are important to the male - so evolutionarily, the bird may end up compromising on tail length to make sure he both reproduces and survives.}

image

{Intuitively, we expect that exaggerated male traits (like super-long tails) would decrease locomotor capacity, resulting in lower survival rates due to predation.} Despite only mixed empirical support for such locomotor costs, recent studies suggest these costs may be masked as a result of the evolution of compensatory mechanisms that offset any detrimental effects.

{What are compensatory mechanisms? Imagine if that bird with the long tail-feathers developed longer wings, that enhanced its flying abilities. It might offset some of the survival costs of the long tail.}

In this study, {Skye} provides a comprehensive assessment of the importance of potential locomotor costs that are associated with improved male-male competitive ability by simultaneously testing for locomotor trade-offs and compensatory mechanisms. For males of the Asian house gecko (Hemidactylus frenatus), both fighting capacity and escape performance are likely to place conflicting demands on an individual’s phenotype.

image

Males that are highly territorial and aggressive are more likely to require greater investment in jaw size/strength in order to compete with rival males; {Skye} found that males with larger heads had stronger bites and showed greater prey-capture and fighting capacity. This performance trade-off was amplified for male geckoes with larger heads when {they were} sprinting up inclines.

image

{So, what does this mean? Geckoes with large heads are better at fighting and better at capturing prey, but may be worse at evading predators themselves. A compensatory mechanism would be something - like longer legs - that would enhance their ability to avoid predation.} {However, Skye} found little evidence for compensatory mechanisms that off-set the functional trade-off between bite force and sprint speed.

Ongoing work in this area includes testing the survival of male geckoes with different sized heads in controlled-but-natural conditions.

Bigger *is* Better: Phallus size and male physical performance across temperatures

The second presentation we'll discuss is Robbie's. Robbie's talk - though sadly fraught with technological difficulties - conveyed to the audience the answer to that age-old question:

does a bigger phallus actually mean the male is better?

I won't give away the ending just yet, (or maybe I will ... ) - in mosquitofish, anyway - the answer seems to be yes.

Bigger is Better in all environments: temperature-induced variation in phallus size is a reliable indicator of male physical performance and gamete quality

Males of many organisms possess elaborated structures that are used to engage in fights with other males and/or to attract females during courtship. The size and elaboration of these secondary sexual traits can be affected by the environment via its influence on the condition of an individual male. This link between male condition and the elaboration of male sexual signals is one of the most important mechanisms maintaining the reliability of these traits as signals of male quality.

male elk use extravagant antlers to battle for females

The role temperature plays in mediating the condition of individual males and the size and elaboration of their sexually selected traits is currently unknown. Males of the eastern mosquitofish (Gambusia holbrooki) possess a modified anal-fin phallus (gonopodium) that is used as both a signal of dominance and a stabbing weapon during male-male competitive bouts {as well as to fertilise females}.

image

{Robbie} examined the effect of temperature on the size of this putative sexual signal (phallus size) by chronically exposing males to either 20° or 30°C for four weeks. {He} also tested the influence of these thermal environments on various measures of male quality; including male territorial performance, swim speed and gamete function.

Males chronically exposed to 30°C possessed longer phalluses, greater ejaculate sizes, larger testes and faster sperm swimming speeds than those exposed to 20°C. This is the first study to show that environmental variation in phallus size can be a reliable indicator of male physical performance and gamete quality.

{And what does this mean, and why does it matter? Well, it means that mosquitofish may have higher reproductive outputs in warmer environments, and might do even better than they currently do when climates warm further. In Australia, mosquitofish are invasive and by out-competing and eating eggs and young of natives, they are aiding the decline of native fish populations.}

Not good. Who knew that global warming would increase phallus sizes ...

Death After Sex in the Australian Bush

Charleston wasn't just about pizza and beer, though with any scientific conference that's always a part of it ...

First up, we'll hear about Jaime's poster. Jaime did a 1st class honours degree in the lab, studying the way Rhinella marinus (cane toad) tadpoles respond to the presence of predators in their environment. But that's not what she was presenting here ... Jaime also recently was accepted into the PhD program at UQ to study quolls on Groote Eylandt, and she was keen to get the word out there about her new study system.

Now.

More about quolls and sex and the bush, as conveyed by Jaime and her co-authors on the poster, Robbie and Billy {with clarifications from me along the way}

image by Candice Bywater

Death after Sex in the Australian Bush: determinants of survival and reproduction in males of the world’s largest semelparous* mammal {*meaning they die after breeding!}

The northern quoll (Dasyurus hallucatus) is a medium-sized (approx. 1 kg) predatory marsupial previously common across the entire top-end of Australia. This species is the largest known semelparous mammal in the world, which means mating is highly synchronous, males live for only one year, and males undergo total die-offs soon after the mating season.

Such population-wide male die-offs are presumably due to the physiological stress of procuring copulations and the intense fighting among males. A small proportion of females will survive to produce a second litter, but there are no documented cases of survival to a third breeding season. The young are born after a short gestation period and then carried in a rudimentary pouch for approximately 60-70 days.

Females will then leave young in dens while they forage, returning to suckle until young are independent at 4 – 5 months. Both sexes are solitary throughout the year with a home range averaging 35 ha for females and approximately 100 ha for males during the breeding season but varies greatly between individuals.

During {Jaime's} study, {she} will be investigating the morphological and performance determinants of both survival to reproductive-age and fecundity among males of this species on Groote Eylandt, an Indigenous-managed island off the coast of the Northern Territory. Northern quolls are still highly abundant on this island and this population offers a unique opportunity to understand the evolution of this extreme mating system and the role physical performance plays in the reproductive success of males.

We can't wait to hear more!

Our Collaborators

We've just added a new page that highlights some of our lab's key collaborators - with links to their webpages and information about what they do, this is a great resource for anyone interested in being part of our research group! Check it out here.

A Little Bit About Our Research on Performance

The basis of our lab's research is performance - performance of animals, including humans, in the context of their biotic or abiotic environments. We're interested in trade-offs between traits such as speed and endurance; the ways that changes in temperature or oxygen levels or life stages affect performance; and - in the case of sport - we're interested in optimising performance levels.

Currently, we're looking at projects such as:



1. Skill, balance, and athleticism in soccer performance (humans)

See the following posts for more detail:
Research and Innovation in Soccer (on our soccer website)
Measuring Individual Performance in a Team Context (on our soccer website)
The Importance of Effective Receiving and Passing (on our soccer website)
Assessment of Receiving and Passing Skills (on our soccer website)

 

 2. Weapon strength in signalling animals (crustaceans, lizards)

See the following publications for more details:

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. View abstract here.

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. View abstract here. 

Seebacher F & Wilson RS. 2006. Fighting fit: Thermal plasticity of metabolic function and fighting success in the crayfish Cherax destructor. Functional Ecology 20: 1045-1053. View abstract here. 

crustaceans fighting to establish dominance

3. Tradeoffs in locomotor performance (fish, crustaceans, amphibians, insects, humans)

See the following publications for more details:

Angilletta MJ, Wilson RS, Niehaus AC & Ribiero P. 2008. The fast and the fractalous: tradeoffs between running speed and manoeuvrability in leaf-cutter ants. Functional Ecology 22:78-83. View abstract here.

James RS & Wilson RS. 2008. Explosive jumping: Morphological and physiological specialisations for extreme jumping in Australian rocket frogs. Physiological and Biochemical Zoology 81:176-185. View abstract here.

Wilson RS & James RS. 2004. Constraints on muscular performance: trade-offs between power output and fatigue-resistance in skeletal muscle. Proceedings of the Royal Society of London B 271: S222-S225.

Van Damme R, Wilson RS, Van Hooydonck B, & Aerts P. 2002. Performance constraints in decathletes. Nature 415:755-756. View abstract here.

  

do a male threadfin rainbowfish's streamers affect his swimming?

4. The myriad ways that the abiotic environment (i.e. temperature, pH, UV radiation, oxygen levels, etc) or the biotic environment (i.e. competitors, predators, etc) influences performance (frogs, fish, crustaceans, lizards)
See the following posts for more detail:
Run Gecko Run
Measuring Toad Jumps
Studying Mosquitofish in the South of France

And the following selected publications:
Wilson RS, Lefrancois C, Domenici P & Johnston IA. 2010. Environmental influences on unsteady swimming behaviour: consequences for predator-prey and mating encounters in teleosts In Fish Locomotion: An eco-ethological perspective (Eds Domenici, P & Kapoor, BG). Science Publishers, NH, USA. 

Barth B & Wilson RS. 2010. Life in Acid: interactive effects of pH and natural organic acids on growth, development and locomotor performance of larval striped marsh frogs (Limnodynastes peronii). Journal of Experimental Biology 213: 1293-1300. View full text here.

Condon CHL & Wilson RS. 2006. Effect of thermal acclimation on female resistance to forced matings in the eastern mosquito fish. Animal Behaviour 72: 585-593. View abstract here.

Wilson RS. 2005. Temperature influences swimming and sneaky-mating performance of male mosquitofish Gambusia holbrooki. Animal Behaviour 70:1387-1394. 

Billy measures jumping performance in a toad metamorph