From the field: Studying endangered northern quolls on Groote Eylandt

It's a new year, which means there's new research to be done as I delve into my PhD. But before I start writing about that, I want to write about a somewhat related experience I was lucky enough to have last year.

In August/September, I got to join my labmates Ami, Jaime, and Gwen up on Groote Eylandt, which is a large island off the coast of the Northern Territory owned and run by the Anindilyakwa people. The reason: to help them out with their research on the endangered Northern Quoll (Dasyurus hallucatus).

Catwoman, a pretty little female Northern Quoll ( Dasyurus hallucatus ). 

Catwoman, a pretty little female Northern Quoll (Dasyurus hallucatus). 

A classy addition to any accessory collection. Image credit: Wikimedia Commons. 

A classy addition to any accessory collection. Image credit: Wikimedia Commons. 

Now, if you’ve ever been to Australia, you probably have heard the story of the Cane Toad (Rhinella marina) – even if it’s just via one of the many delightful novelty souvenirs available in Australian tourist shops.

The cane toad is an extremely successful invasive species that was introduced into Australia in 1935 to eat a beetle that was negatively affecting the cane industry (which it didn’t), and since then it has spread down the East coast and across the Northern Territory, and is slowly making its way down the West coast as well. One of the reasons Groote Eylandt is so amazing is because it is one of the few areas up North that has remained cane toad-free. Because of this exclusion, it is the last stronghold population of the endangered Northern Quoll, whose numbers have been decimated via their predation on this toxic species. This makes Groote an ideal location to study the quoll in its natural habitat, as numbers are high enough for recapture studies to generate useful amounts of data.

A magical sunset in the bush next to the highway to Umbakumba.                                              Ami measuring one of our little darlings. 

I was on Groote Eylandt for 5 weeks helping Ami with data collection for her PhD project. As well as stunning landscapes and amazing native animals, Groote Eylandt is also home to a large manganese mine. All animals need some amount of manganese to function, but like any heavy metal it can be toxic in high concentrations. For her PhD, Ami is looking at how quolls from different parts of the island (that have been exposed to different amounts of manganese) perform in motor control and cognitive function tests. We are lucky enough to have access to laboratory facilities at the Anindilyakwa Land and Sea Ranger Station, where we get to work with the Rangers to figure out how to do our research in a way that is compatible with indigenous culture.

We went out every night and set 30-60 traps in one of our three trapping areas various distances from the manganese mine, which we then checked first thing the next morning. If we were lucky, we’d see white spots and hear some angry growling – otherwise it was rather likely that we’d caught one of the other marsupials that populate the area. We then transported our precious bundles back to the lab at the Anindilyakwa Ranger Station where we sexed them, weighed them, took various morphological measures and a hair sample (to get their internal manganese concentration from) and pit- and ear-tagged them.

Alfred, a feisty (and adorable) little male. 

Lastly, we’d gather information on their level of motor control. I won’t give away too many details, but we basically assessed their performance at various speeds and analysed how many mistakes they made depending on the difficulty of the task and the speed at which they performed it. We would expect that as speed and/or “difficulty” of the task increases, the quolls will make more mistakes. The reasons for this are very intuitive and you will probably have observed them in your own life; as you do things faster you have less control over your movements and are more likely to make an error. Similarly, if a task is difficult, you’re more likely to make a mistake than if it’s relatively easy. What Ami wants to know is whether the manganese concentration the quoll has been exposed to enhances this effect – i.e., whether high manganese concentrations affect motor control.

Back to the bush you go.                                                                                                                              Having a sniff out of the corner of his bag. 

Ami also wants to look at whether manganese concentration affects cognitive function in the quolls – but that’s for her to write about! She’ll continue to run these experiments for the next two years, and hopefully get some excellent results. I was very lucky to be involved in helping out with this project, as many of the techniques she used will be helpful in my own PhD.

Although quolls were the main attraction for us, Groote Eylandt has plenty of other amazing qualities that made my trip there one of the most memorable ventures into the field that I’ve ever had. We are extremely privileged to be able to conduct research there, and I learned more about indigenous culture than I ever thought I would. I also saw loads of awesome animals and plants, and got to spend a lot of time in the field – which is definitely one of the best ways to spend it.

A Mertens' Water Monitor (Varanus mertensi) chilling by Milyerrngmurramaja (the "Naked Pools"). These guys are also threatened by ingestion of the cane toads. A Striated Pardalote (Pardalotus striatus) that was nesting next to the Anindilyakwa Ranger Station.

A Burton's Legless Lizard (Lialis burtonis) we found while we were setting traps near Alyangula. A Helmeted Friarbird (Philemon buceroides) next to the highway to Umbakumba.

I’d like to say a huge thank-you to my lab for this opportunity, but most especially to Ami, Jaime and Gwen for teaching me so many new skills and being the best bush-buddies ever. I’m looking forward to future adventures with the Wilson Performance Lab as I start my PhD on another kind of carnivorous marsupial… the Yellow-footed Antechinus (Antechinus flavipes)!

Sunset on the beach at Ayangkwa ("Tasman Point"). 

All images by Rebecca Wheatley unless otherwise credited.

The Grand Slam: How Hard Should You Hit?

Squirrels know what’s going down (or do they)? Image source: Wikimedia commons.

Squirrels know what’s going down (or do they)? Image source: Wikimedia commons.

The trade-off between performance and accuracy is a problem faced by a lot of different animals in a variety of situations. For example, consider a squirrel running along a bare branch to get from one tree to another; the faster it runs, the less time it spends exposed to predators. However, as the squirrel runs faster, it also increases its chances of mis-stepping and falling to its potential doom. 

So, to get the best of both worlds, the squirrel needs to optimise its running speed depending on its chance of slipping (the width of the branch) and the cost of falling off (the height from the ground).

These sort of performance/accuracy trade-offs are also commonplace in the human world. How fast should you smash out a text message to your supervisor asking him (politely) to email back your latest draft before the number of typos makes the whole thing unintelligible?  In particular, these trade-offs are of a great deal of interest in elite sports. An awesome example of a sport where this trade-off is of utmost importance is in singles tennis.

Serving hard: Heather Watson, Roger Federer and David Ferrer. Image source: Wikimedia commons.

In tennis, it’s pretty well accepted that if you serve really hard, it’s more difficult for your opponent to return the ball. But the harder you serve, the more likely it is that you’ll miss the service area and fault. So, players will usually belt it out on their first serve, but if they miss the first serve they’ll hedge their bets and serve softer the second time round to make sure they don’t double fault.

A/Prof Robbie WilsonDr Chris Brown and I have been testing this idea about performance trade-offs and optimal strategies using data from the men’s singles in the 2013 Australian Open. We’ve found this observation to be generally true: the probability of winning the point increases as the serve speed approaches its maximum, but the probability of faulting increases as well (for most players – some players are really consistent at getting it in regardless of how fast they serve). This was reflected in the frequency of high serve speeds in the first and second serves.

Jérémy Chardy, Andy Murray and Janko Tipsarevic. Image source: Wikimedia commons.

We’ve also constructed an optimality model which predicts the optimal serve speed taking into account the probability of faulting and the cost of a fault. An optimality model is, in essence, a mathematical model where you input the risks and rewards of a specific situation for a given individual, and it will tell you the optimal response for that individual if it wants to both minimise the risks and maximise the rewards. 

Optimality modelling is useful because it allows us to calculate the optimal response of specific individuals to any situation. We are looking at whether their opponent’s world ranking (ability to return a fast serve) and the point they’re going for or defending against (normal, game, set or match) affects their serve speed in relation to their optimum, but more on those results later.

Rafael Nadal, Caroline Wozniacki and Jérémy Chardy. Image source: Wikimedia commons.

We hope that our research can teach us more about how animals optimise their behaviour and physical efforts to improve their chances of successfully performing a given task. Depending on what we find, we might even be able to offer specific recommendations to tennis players wanting to improve their service game – who knows what the future might hold!

Andrew Hunter, a PhD student in our lab, is looking at performance/accuracy trade-offs in soccer. Will the results be similar between an individual and a team sport? We don’t know yet, but it will be interesting to find out.

Novak Djokovic, Agnieszka Radwańska and Venus Williams. Image source: Wikimedia commons.

Tag Cloud Block
This is an example. Double-click here and select a page to create a cloud of its tags or categories. Learn more

The boldest gecko: personality in a reptile

Today on the blog we're happy to have former Wilson Honour's student, Rebecca Wheatley, who describes her thesis work on gecko personality. Rebecca's currently working as a research associate in the Wilson lab, and plans to start a PhD next year. You can find out more about Rebecca on her science blog, The Adventures of the Integrative Ecologist.

Animal behaviour is a big field - and it's constantly expanding as research reveals gaps in our understanding of why animals do the things they do. One topic in animal behaviour that holds a great deal of interest for me is that of animal personality. This is a relatively new concept and, frankly, it's a little bit controversial. 

The word "personality" conjures up a variety of mental images, most of which pertain to one animal in particular: us. It goes without saying that people have different personalities; we experience it every day. But do other animals have personalities as well?

Image: Great tit (Parus major), beadlet sea anemone (Actinia equina) and pumpkinseed sunfish (Lepomis gibbosus); three species that display animal personality, from very different groups. Image source: Wikimedia commons.

In animal behaviour, the term "personality" is defined as consistent differences in behaviour displayed by individuals. An example of a personality trait is how an individual responds to a threatening situation, termed boldness or shyness. Bold individuals are undaunted by threatening situations and will approach the stimulus, while shy individuals will stay away or hide.

There are heaps of different personality traits that have been studied, including boldness, exploratory behaviour and aggression, amongst many others. Individuals' "personalities" are thought to range along a proactive-reactive continuum, where proactive individuals are aggressive and bold while reactive individuals are more passive and shy (sound familiar? It's not unlike a simplified version of the extroverted/introverted behaviour displayed by people).

There's growing evidence that "personality" is present within many groups of animals. Despite this, we don't really know much about what determines an animal's place along the proactive-reactive continuum or why this variation exists.

Image: My study species: the Asian house gecko (Hemidactylus frenatus). Image credit: Wikimedia Commons (1 & 3) and Rebecca Wheatley (2).

During my honours project, I investigated"personality" in male Asian house geckos (Hemidactylus frenatus). I measured the anti-predator behaviour (a proxy for boldness) of 100 geckos by filming each gecko for one hour and then by calculating the proportion of time it spent inside the shelter in its terraruim. 

Each gecko was measured under three different treatments:

  1. "empty terrarium": where nothing (aside from the shelter) was added to the terrarium, to give me a measure of each gecko’s normal amount of anti-predator behaviour
  2. "terrarium with novel object": where I added a novel object to the terrarium, to see what happened to their anti-predator behaviour when something new was added to the environment
  3. "terrarium with threatening stimulus": where I added a threatening stimulus, to see how their anti-predator behaviour changed when something scary was added to their environment

I found that different individuals reacted to the treatments in different ways, but the overall trend looked like this:

We can see that when a novel object was added to the environment, the geckos' anti-predator behaviour generally decreased when compared to their standard level of anti-predator behaviour. This might be because they wanted to check out the new object to make sure it wasn't food or some other valuable resource. 

However, when I added a threatening stimulus, their anti-predator behaviour jumped back up again to around the same as its standard level. 

So it seems that the threatening stimulus effectively cancelled out the novel object effect.

How do we know if these behaviours constitute as "personality"?

Well, I found that while different individuals displayed consistent anti-predator behaviour within treatments, they also responded to the treatments in different ways. Some displayed more anti-predator behaviour when the environment was altered (were "shyer"), while others displayed less (were "bolder"). 

Therefore, from our definition, we can see that their anti-predator behaviour is a personality trait: they display consistent differences in behaviour that are context-specific.

Checking on my gecko housing set-up. Image credit: Amanda Niehaus.

But why do individuals have different personalities?

Previous research has found that a few things can be associated with an animals' boldness or shyness. A large body mass is often associated with a bold personality, which is probably because heavier individuals are usually larger and more likely to win in a fight (so they have a good reason to be bold). Similarly, individuals with a hard bite force, a strong claw pinch or any other performance trait which would give them an advantage in a contest are usually bolder as well. 

The possession of traits that might make it easier for them to escape from a predator in a pinch, like fast running speed, have also been associated with boldness.

 In addition, resting (or "standard" for reptiles) metabolic rate has been linked to animal personality; it's thought that bolder, more aggressive individuals need a higher metabolic rate to keep up with their energetic demands.

I investigated how some of these traits interact to effect boldness in my geckos. I measured each gecko's mass, standard metabolic rate, maximum running speed and maximum bite force and analysed their interactive effects on anti-predator behaviour. Contrary to what I expected (and to what the literature would lead us to predict), I found that none of these traits affected anti-predator behaviour. This could be due to a few different things: one possibility is that boldness and shyness in Asian house geckos has a hormonal basis. It could also be that "personality" in geckos develops based on experiences rather than any specific physiological or performance trait. To discover the answer to this question, further research into the interactive effects of such traits on personality needs to be done.

One of my geckos in his metabolic chamber. I did all my metabolic tests during the day (when they are least active, being nocturnal animals) so I could get an accurate estimate of their resting (standard) metabolic rate. Image credit: Amanda Niehaus.

Anyway, why does it all matter – why does "personality" even exist?

The fact is there are costs and benefits to being both proactive and reactive. Proactive individuals are bolder and more aggressive, so they are usually better at holding territories and getting laid – but they're also a lot more conspicuous to predators, so they tend to "live hard, die young". Reactive individuals, on the other hand, might not have the best real estate or as many mates at any given time, but their shy behaviour means they usually live longer. So, if we imagine an ecosystem where predation is low, it's better to be proactive and reap the benefits without the risk of being eaten. But if the ecosystem changes (for example, a bunch of predators move into the neighbourhood) and all the proactive guys die off – who is left? This is the most popular theory as to why different personalities exist; so that if conditions change quickly, some individuals survive and the population continues.

Although extremely interesting, these personality experiments were only one small aspect of my honours project, which aimed to answer questions about fighting ability (resource-holding potential) and fighting strategies. More on that later!

- by Rebecca Wheatley

Bit of a teaser for the rest of my project. Image credit: Amanda Niehaus.