The allee effect: an effective ally to achieve eradication of invasive species?

Posted by Hester Williams @HesterW123

The rise in biological invasion, strongly related to increasing international trade and travel, is creating global ecological and economical challenges.

The process by which biological invasions occur can be divided into three phases: arrival, establishment, and spread. Early intervention in the form of detection and eradication can be one of the most cost-efficient approaches. Eradication is the deliberate elimination of an invading species from an area, and is greatly assisted by prompt detection when the newly established population is still small and not widely spread.

Given the perceived difficulty of eliminating all individuals of a species, the practicality of eradication has often been questioned. However, recent population studies indicate that low density populations of a variety of species are governed by Allee effects and this may facilitate eradication. Allee effects may arise from a variety of mechanisms (e.g. mate-location failure, failure to overcome host defences, failure to satiate predators) and create a population threshold, below which population growth rate is negative. Consequently, eradication may not require directly eliminating all individuals in a population; instead, it may only be necessary to reduce the population below the Allee threshold, and extinction will proceed without further intervention.

The loss of habitat and fragmentation, which are detrimental to rare and endangered species, are complementary in attempts to eradicate an invasive species from an area. Although habitat loss is not a cause of an Allee effect, it can reduce population size such that the population could then become succeptible to an Allee effect. Fragmentation of an invasive species population (through management actions such as host removal /fragmentation) could result in reduced patch-to-patch dispersal as well as reducing the population densities in each fragmented patch to below the Allee threshold. Thus, sufficiently small and distant patches could lead to extinction of the population.

My studies use Neolema ogloblini, a biocontrol agent for Tradescantia fluminensis, as proxy for an invasive insect pest species (Fig 1).

Fig1

Fig 1: The leaf beetle, Neolema ogloblini, a biocontrol agent for Tradescantia fluminensis, with typical adult damage.

Experiments completed last summer have indicated that at small population sizes, establishment of this beetle is moderated by an Allee effect. This summer I will test the effectiveness of host removal as a management tool to achieve eradication by exploiting the Allee effect. I will remove a selected number of host patches within a meta-population of Neolema ogloblini, thereby fragmenting the remaining population and in turn subjecting it to Allee effects to achieve eradication (Fig 2).

Fig2

Fig 2: Host removal as management tool to achieve eradication through exploitation of the Allee effect. A selected number of host patches within a meta-population of Neolema ogloblini will be removed (denoted by white patches), fragmenting the remaining population and in turn subjecting it to Allee effects to achieve eradication.

Results of this experiment will ultimately give guidance on what eradication approaches are more or less promising for particular invasive species.

 

Hester Williams is a PhD candidate in the School of Biological Sciences, University of Auckland and is stationed with the Landcare Research Biocontrol team in Lincoln, Canterbury. She is interested in invasion processes of both insect and plant species. Hester is supervised by Darren Ward (Landcare Research/University of Auckland) and Eckehard Brockerhoff (Scion), with Mandy Barron (Landcare Research) as an advisor. Her studies are supported by a joint Ministry for Primary Industries – University of Auckland scholarship. The project is an integral part of an MBIE program “A Toolkit for the Urban Battlefield” led by Scion.

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Why do tropical rat eradications fail?

Posted by James Russell @IsldJames

The answer is self-evident: because we didn’t kill all the rats. However, the answer to the question “why didn’t we kill all the rats” is more complex. Tropical rat eradications currently fail more often than those in temperate or polar regions (16.1% vs 6.3%). If we discount operational reasons (i.e. the eradication wasn’t undertaken properly), the two prevailing biological hypotheses are that either with rats constantly breeding some pups may be able to survive and re-populate the island, or food is so abundant that not all adult rats diet switch to the poison bait.

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A radio-collared rat on Reiono Island (Photo: James Russell)

Experimental rat eradications have proven very profitable in the past for advancing the science of rat eradications, but not everyone wants to allow their rat eradication for conservation to be an experiment, particularly when this increases the risk of failure. This week a team of scientists from University of Auckland (Araceli Samaniego, Markus Gronwald, James Russell) have been undertaking an experiment in association with a tropical rat eradication on Reiono Island in French Polynesia. The 22 hectare island will be treated with poison to eradicate the rats which are widespread across the otherwise relatively pristine island dominated by Pisonia forest and native seabirds and reptiles.

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An alive 5 day old rat pup (Photo: James Russell)

The team have radio-collared over 60 female rats and will track them throughout the course of the eradication. They will monitor their nests to determine the likelihood of any baby rats surviving over the two weeks of the eradication. This intensive monitoring effort will reveal the most detailed data yet on the behaviour of rats during a tropical eradication campaign, and hopefully inform future rat eradications on tropical islands so that they may be as successful as those undertaken in temperate and polar regions around the world.

For more information see the special issue of Biological Conservation on tropical rat eradication.

Conservation in Aotearoa in 2030

Posted by Cate Macinnis-Ng @LoraxCate

The theme for this year’s University of Auckland Winter Lecture Series is Aotearoa in 2030. James Russell and I were invited to speak about conservation in Aotearoa in 2030. James covered the vision for Predator Free 2050 and I talked about some things we need to think about to make the most of the One Billion Trees policy. In short, we need to think carefully about which trees we plant where.

You can view this recording of the talk for more details.

 

Maintaining biodiversity in urban areas

Post by Anna Frances Probert @AFProbert

Urbanisation has come at a cost to greenspaces and biodiversity. Worldwide, pressures for development to sustain our growing human population has led to the loss of vast areas of natural habitats and agricultural land. The associated loss of habitats that sustain populations of native species is considered a driving force in global biodiversity declines.

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Greenspace in a very urban setting; Central Park, New York. Photo: Walkerssk Pixabay

Greenspace is a general term used to characterise vegetated areas of land, whether that be a natural ecosystem such as forest, or a park and recreation area. The benefits of greenspace are broad-reaching; greenspaces can function to increase the quality of living and well-being of residents and visitors to the area. Growing evidence supports the notion that greenspace is an important component of healthy urban living, and greenspace is now a priority area for urban planners. Furthermore, greenspaces provide habitat for biodiversity, providing pockets of refuge within the urban matrix, and allowing the movement of species across the landscape. The protection of greenspace is therefore an important priority to maintain and promote biodiversity in urban areas.

At a smaller scale, urban gardens can act as a type of greenspace, particularly when interconnected with other gardens. Urban residents can therefore play an important role in the maintenance of native biodiversity, by using their gardens and other outdoor spaces in ways that support populations of native birds and invertebrates. Promoting biodiversity in smaller pockets can build up to become part of larger habitat and movement networks that support populations throughout the landscape.

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A bug hotel provides habitat for invertebrates such as wēta. Photo: anpe Pixabay

So what can you do to help in your backyard? Well, many councils are now beginning to provide excellent online resources for community members learn about how to support local wildlife. Whether it is building a wētā hotel in your backyard or porch, planting kaihua (a native jasmine, which I have climbing inside my central Auckland apartment) and other native plants, or keeping your cat indoors and installing predator traps, there are many ways we can participate in enhancing our local environment, for both the benefit of people and biodiversity.

 

 

 

MeblogAnna Probert is a PhD student in the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is using ants as a model to assess the risk posed by exotic invertebrates to native ecosystemsShe is supervised by Margaret StanleyJacqueline Beggs, and Darren Ward.

When setting the scene, birds are the unsung heroes

Posted by Ellery McNaughton @EJ_McNaughton

There’s a lot of discriminating going on in Hollywood. You’ve probably heard of whitewashing, but what about hawk-washing? Chances are you’ve seen it in action. When some craggy mountaintop or rugged landscape appears on the screen, an eagle will fly by and give a majestic screech. Only problem is, that majestic call isn’t actually an eagle at all. It’s a red-tailed hawk. Apparently the patriotic symbol of America just doesn’t sound cool enough for the silver screen. Birds that sound cool can also nab roles from those more geographically qualified. A prime example of this is the laughing kookaburra, found only in Australasia, yet magically heard in movie jungles all over the world.

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The A-listers: Red-tailed hawk, common loon and laughing kookaburra

Inaccurate or not, these birds and others do a lot of scene setting without us even realising. An owl hooting at night is somehow instantly spooky, despite it being what owls naturally do. Nothing says wilderness like a common loon, which is apparently all the reasoning Marvel needs to stick one on an alien planet. It does make me pity American bird enthusiasts, whose suspension of disbelief in movies doesn’t have the same shiny protective coating of ignorance that mine does. I accepted the sound of a common loon as an icon of haunted wilderness way before I knew the actual bird existed. The only twinge of recognition I get is hearing bellbirds in elven woods when watching Lord of the Rings for the hundredth time.

The ability of bird calls to invoke a particular idea or emotion is something I’ve been thinking about whilst going through the dawn/dusk chorus audio data I collected for my thesis. Rugged up with a winter dressing gown and hot water bottle, I didn’t expect to feel like summer was just around the corner. And yet, thanks to Turdus merula, I did.

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Blackbird calls on a spectrogram – reminds me of impending summer. Also of Van Gogh.

Merely the recording of a blackbird singing at dusk was enough to get me dreaming of daylight savings and warm summer nights. It’s an interesting reminder of just how much meaning we unconsciously attach to bird calls, whether they be in movie soundtracks or the urban soundscapes we live in.

Ellery McNaughton is a PhD student in the Centre of Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. Her project investigates the effects of a city-wide changeover in streetlight technology on urban bird behaviour and ecosystem function. She is supervised by Margaret StanleyJacqueline BeggsKevin Gaston (University of Exeter, UK) and Darryl Jones (Griffith University, Australia).

Going for birds: my top 6 places for bird watching in New Zealand

Posted by Daria Erastova @Kuukso

My big dream was to study New Zealand native birds. To my utter happiness, I finally joined the friendly Ecology Ngātahi labgroup under the supervision of Margaret Stanley to study ecology of urban native birds. However, I have just started my PhD project and I hope to give you some insights on that later. Instead, I will share some of my experiences birdwatching in New Zealand. Birds of a feather flock together – I found this pastime quite popular in New Zealand, so today I share my top six places to find native birds!

No. 6: Dunedin Botanic Garden, Dunedin.

The famous Dunedin Botanic Garden lies within the city’s green belt and is very big. This, along with numerous old and flowering trees growing there makes this place an excellent haven for birds. Many native species scurry here and there: tui, bellbird, silvereye, fantail etc. There is also an aviary with captive kea, kaka and kakariki.

Sylvereye

Silvereye

No. 5: Point England Reserve, Auckland.

This spacious reserve connects with other coastal reserves and is maintained, allowing you to spend a whole day there. This amazing place enables you to get  a wildlife experience while staying New Zealand’s largest city. Here you would can find a variety of shore and forest birds. I counted 25 species in a day, including natives like shelduck, kereru and rare little black shag.

Kereru

Kereru

No. 4. Urupukapuka Island, Bay of Islands.

I was not keen to go there. Urupukapuka proved I was wrong as it turned out to be an outstanding place for birdwatching. In fact, I beat my personal record and identified 27 species in 3 hours! My most interesting encounters were banded rail, New Zealand dotterel, tomtit and North Island robin.

shelduck

Shelduck

No. 3. Otago Peninsula, Dunedin.

Except for the famous Royal Albatross Colony, where you can also spot Stewart Island shag, and the Penguin Place, with grumpy yellow-eyed penguins, there are other places worth visiting. For example, the Hooper Inlet, inhabited by sacred kingfisher, white-faced heron, grey teal and swamp harrier. The other place is Portobello Bay with royal spoonbill, pied oystercatcher and the cutest little shag. Finally, go to Tomahawk Lagoon for pied stilt or spur-winged plover.

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Little shag

No. 2. Tawharanui Regional Park, Auckland.

What is special about this beautiful peninsula is that it is surrounded by a pest-proof fence and has a variety of habitats, including old forests with kaka (you are highly likely to see or hear one), river thickets with spotless crake and seashores with pipits.

No. 1. Tiritiri Matangi, Hauraki Gulf.

This reserve does not need any introduction being one of the most popular tourist attractions in Auckland. After predator eradication and forest replanting the island became the bird paradise. There you all the chances to have a close encounter with species you would never or hardly ever see anywhere else, e.g. little spotted kiwi (one passed 25 cm away from me!), takahe, kokako, brown teal, stitchbird and many more.

I hope this list was useful and enjoyable for all nature lovers. It is based on my limited experience, and there are many other fantastic places, which I am eager to explore. Therefore, if you need a volunteer for your bird fieldwork or a companion on a birdwatching trip, please feel free to contact me.

 

kokako

Kokako

 

DariaphotoDaria is a PhD candidate studying the influence of garden sugar feeders on native bird behaviour and health, and whether feeders alter the contribution these birds make to pollinating indigenous plants. She is supervised by Margaret Stanley, Kristal Cain and Josie Galbraith.

 

Coevolution in exotic herbivores and weeds

Posted by Melissa Kirk @MGKir_04

Evolution and adaptation

Exotic species have the potential to adapt and rapidly evolve in their new introduced ranges. This can have multiple consequences including changes to their host preference, defence mechanisms, growth rates and biomass, climate tolerance, fecundity and phenology. These changes can lead to an increase in abundance, range expansion, and a difference in their overall impacts.

birds evoSuch adaptations are highly likely due to the multiple new selective pressures they may encounter. For example, new selection pressures may occur as they encounter new competitors, new climates and new habitats. These adaptations and trait shift changes can occur in relatively short time periods, within a few generations. The absence of competitors and natural enemies can lead to relaxed selection, and thus a change may occur through a non-adaptive shift. A non-adaptive shift may not translate to a genetic shift initially; however, such shifts can lead to reproductive isolation and subsequently speciation.

Adaptations in plant-herbivore systems

There are two key theories behind why many plant species become weeds: the ‘enemy release hypothesis’ and the ‘novel weapon hypothesis’. The theories state that either the lack of natural enemies in the new introduced area or the presence of novel defence mechanisms which allows no or low herbivory to occur in the new environment. Thus the role of coevolution between weeds and specialists herbivores has also been attributed to plants invasiveness. If a plant has escaped its specialised herbivores, there is no need to produce costly defence mechanisms and this energy and resources can be used for growth and increased competitiveness in its new introduced range. An example of this is when the wild parsnip, Pastinaca sativa invaded the US, and after many generations without its coevolved enemy the webworm, Depressaria pastinacella its levels of defence chemicals reduced. However, after the webworm became established within the US and the plant-herbivore system were reunited; rapid evolution resulted in increased levels of defence chemicals (Zangerl & Berenbaum, 2005).

Re-association: wild parsnips and webworms in New Zealand

webworm

Image source: Tarmo Lampinen, 2013

Wild parsnips also occur within New Zealand, like in the US, parsnip populations went many years without the webworms. It wasn’t until over 150 years after the establishment of the wild parsnips that the parsnip webworms were accidentally introduced into New Zealand. A previous study found that for wild parsnips in NZ, the re-association with their natural enemy the webworm did not result in an increase of defence chemicals, rather an increase in plant size (Jogesh, Stanley & Berenbaum, 2014). Therefore a switch in strategies seems to have occurred from resistance using chemical defence to tolerance via the plants size, however, whether this change is a true adaptive shift needs to be investigated.

As part of my PhD research on the ‘rapid evolution of exotic species’ I am planning on researching exotic herbivores and weed interactions, and how they can influence each other’s evolution. For this I am planning on investigating the wild parsnip and webworm interaction in NZ. I am also planning on investigating the interaction between nodding thistle and its exotic herbivores in NZ, like that of the wild parsnip it is thought that the presence of the nodding thistles natural enemies has influenced the traits and evolution of the plants growth and reproduction.

Key references:

Blossey, B., & Notzold, R. (1995). Evolution of increased competitive ability in invasive nonindigenous plants: a hypothesis. Journal of Ecology, 83(5), 887-889.

Callaway, R. M., & Ridenour, W. M. (2004). Novel weapons: invasive success and the evolution of increased competitive ability. Frontiers in Ecology and the Environment, 2(8), 436-443.

Jogesh, T., Stanley, M. C., & Berenbaum, M. R. (2014). Evolution of tolerance in an invasive weed after reassociation with its specialist herbivore. Journal of evolutionary biology, 27(11), 2334-2346.

Müller-Schärer, H., & Steinger, T. (2004). Predicting evolutionary change in invasive, exotic plants   and its consequences for plant–herbivore interactions. Genetics, evolution and biological control, 137-162.

Zangerl, A. R., & Berenbaum, M. R. (2005). Increase in toxicity of an invasive weed after    reassociation with its coevolved herbivore. Proceedings of the National Academy of Sciences, 102(43), 15529-15532.

Melissa is a PhD candidate within the Centre for Biodiversity and Biomesecurity, School of Biological Sciences at the University of Auckland. She is studying rapid evolution in exotic species, and is supervised by Darren Ward, Thomas Buckley and Quentin Paynter. Email: mkir508@aucklanduni.ac.nz

Simple Words and Storytelling: Communicating Science to a General Audience

Posted by Olivia Rooke-Devoy (BSc(Hons) Candidate)

If a tree falls in the woods and [we don’t communicate it to someone], does it make a sound?

How important is it that scientists communicate and disseminate their ideas to the wider public?

fallentree

Credit: Miri Schroeter

Scientific communities now face climate change denial, anti-vaccination movements, ‘detox’ diets and, bizarrely, a resurgence of Flat-Earth believers. In view of these challenges, it seems that science communication is just as important as the science itself. Ultimately, by educating societies, we as researchers encourage better social and political decision making.

However, science communication is challenging. David Chambers’ well-known ‘Draw a Scientist’ test (1983) demonstrates that, from a young age, people view scientists as aloof and antisocial. My own research of urban lawns in Auckland has stirred controversy. Many people have rejected the premise immediately: “I like your idea, but I won’t stop mowing my lawn!”. Preconceived notions of science and the emotive subjects we study make for critical (and often unfriendly) audiences.

Faced with these difficulties, how do we communicate complex scientific ideas, so general audiences understand? Common techniques, such as using less jargon, sound great in theory but are hard in practice. For example, the Ten Hundred Words of Science blog challenges scientists to use the 1000 most commonly used English words to describe their research. Here’s my own attempt:

“What are the impacts of varying mowing regimes on lawn species assemblages in urban lawns?” becomes “what happens if city people cut green low-growing things less?”

Have a go at the challenge yourself.

Explaining scientific ideas in a straightforward way is difficult. However, using ‘simple’ language and crafting a science narrative makes our subjects accessible. Storytelling in science, taking the form of analogies and personal stories of successes and struggles, connects many types of people. This form of communication opens science to previously-excluded groups and makes science more inclusive and diverse.

Contemporary communication is instantaneous and global. In this modern age, what is a ‘scientist’? Overall, I believe that part of what makes a scientist is the ability to communicate ideas. If a tree falls in the woods and you don’t tell me, how can I care that it made a sound?

Further Reading:

Chambers, D. W. (1983). Stereotypic images of the scientist: The draw-a-scientist test. Science Education, 67(2), 255–265. https://doi.org/10.1002/sce.3730670213

Salmon, R., & Priestley, R. (2015). A future for public engagement with science in New Zealand. Journal of the Royal Society of New Zealand, 45(2), 101–107. https://doi.org/10.1080/03036758.2015.1023320

 

Olivia is an Honours student at the School of Biological Sciences, University of Auckland. Her research is focused on encouraging low-cost, biodiverse lawns in Auckland. She is supervised by Dr Bruce Burns. For further information regarding this research, please visit https://urbanlawnsproject.weebly.com/

Selective reporting: The abuse of statistics

Posted by Andre M. Bellve (MSc Candidate)

As a quick preface – what I am talking about in this post isn’t new or revolutionary. My intent with this blog is to package some of the facts in a more digestible form and hopefully steer my fellow biologists to better practice.

When we carry out statistical significance tests (I.e. ANOVAs, t-tests, etc) there are two types of errors associated with them: False positives: falsely rejecting the null hypothesis, H0, and; False negatives: falsely accepting H0. Every test has these two errors in them and they are inversely proportionate to each other. A significance level of 0.05 means that 5% of the time we will incorrectly reject the null hypothesis. This is the basis of selective reporting, A.K.A p-hacking. Collectively, we have (for the most part) deemed a 5% cut-off as acceptable, at least when we aren’t betting on human lives, and I tend to agree.

What if the chance was higher though? If there was a 10% or 25% chance of false positive, would you still trust your results? You might be thinking: “Well that’s silly Andre – who cuts off their p-values at anything higher than 0.05? ” Well here’s the catch: if you carry out two significance tests, and both have a cut-off for significance at 5%, then the chance that there is a false positive is no longer 5% – it is much higher. This inflating of the overall error rate is the basis of p-hacking. The chance of a false positive is also increased when making pairwise/multiple comparisons!

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Credit: Statistical Statistic Memes via Facebook

Now this isn’t the end of the world – you can correct for it. The read significance level that you set as your cut-off defines the overall error rate of your experiment – both the type I and II error rates. If you are doing several tests, then you have to correct for the increased chance of a false positive. Fortunately, it’s relatively easy to do! There is the extremely conservative Bonferroni’s correction where you divide your significance level by the number of tests you are doing, which is appropriate in some cases (i.e. when it’s a case of life or death). This isn’t popular among biologists as we often deal with very noisy data and it can be hard enough to pick up a signal as it is. For this reason, the less conservative False Discovery Rate (FDR) correction works well when lives aren’t on the line, as it typically leaves at least one significant result without sacrificing the integrity of your analysis. This is not an exhaustive list and you can read more about different methods for correction here.

Selective reporting happens a lot. One recent example came out of the sensory science food labs from Cornell University: Brian Wansink, director of the Food and Brand lab at Cornell, boasted online that a volunteer research assistant of his was able to take a “failed study which had null results” and produce ‘significant’ results from it (Science of Us, 2016). However, careful investigation of the published papers yielded multiple errors and inconsistencies suggesting that the research assistant had ‘p-hacked’ the data to produce these results, although it seemed she had done so unwittingly. It is this kind of behaviour that brought about an analysis by Ioannidis (2005) which found that most published research findings are actually false. The incorrect use of these methods can put at risk the objectivity of the traditional scientific method and create issues of credibility for the scientific community. With more “fake news” and anti-science rhetoric being thrown around than ever before the last thing we need are blows to our credibility or any more fuel being added to the tangerine tire fire that is my president.

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Image Credit: politicususa.com

References

A Big Diet-Science Lab Has Been Publishing Shoddy Research — Science of Us. (n.d.). Retrieved April 8, 2017, from http://nymag.com/scienceofus/2017/02/cornells-food-and-brand-lab-has-a-major-problem.html

Ioannidis, J. P. (2005). Why most published research findings are false. PLos Med, 2(8), e124.

 

 

Don’t mention the P word

Posted by Tom Bodey

Scientists are always trying to communicate their research and ideas across a wide spectrum of media to varying degrees of success (and I can already feel the hoisting of my own petard here). Some of the difficulties arise because a researcher can apply caution and caveating to their results, whereas recipients may prefer to see a clear-cut outcome that makes for more straightforward decision-taking for example. However, scientists do not always help themselves, either by using jargon, or through the avoidance of terms because of the connotations they may imply.

For my latest research I have decided to enter one of these minefields by looking at individual variation in behavioural responses – you see, I’ve done it myself. This variation, particularly if examined across contexts, has been given a range of names within the scientific literature – behavioural syndromes, coping styles, behavioural tendencies – all of which shy away from the dreaded p word – ‘personality’. Now, of course, there are obvious reasons why a researcher may choose to avoid this word, and certainly to use it within air quotes. After all, without becoming Dr Doolittle, it’s pretty hard to get into a non-human head to actually assess their personality, and what you have instead is the examination of a handful of behaviours where individuals differ in their responses.

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Welcome to the office. Rakitu Island study site – you don’t get many laboratories with views like that.

However, even on these highly simplified ‘personality’ scales, it is becoming increasingly obvious that individual animals often differ substantially, and also consistently, in their behaviour. For example, some individuals from species as different as prawns, hyenas and albatross can be bolder, more active, or more social than others, and this variation can then affect other aspects of their lives such as how they find food. These differences are especially intriguing as the maintenance of variation stands in contrast to the movement of species towards a fitness peak. In order to maintain variation, there must be situations in which one set of behaviours are beneficial, and contrasting situations where different individuals prosper – any peak must shift through time or space.

Not content with dipping my toe into an area with such linguistic juggling, I thought I would combine this with invasive species – another area where terminology can take on unfortunately loaded connotations – by looking at individual variation across a range of niche dimensions in everyone’s favourite critter, the humble rat. The Chinese, of course, recognise the rat as the first animal within their zodiac cycle, embodying alertness, spirit and intelligence (as well as being timid, devious and gossipy to balance it out). New Zealand is ‘blessed’ with three species – all invasive and globally widespread – the Brown/Norway Rat Rattus norvegicus, Black/Ship Rat R rattus and the Pacific Rat/Kiore R exulans. I’ve been catching wild rats on offshore islands in the beautiful Hauraki Gulf, running them through behavioural trials in the field before releasing them in order to do it all again the next day, and the next.

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Taking pictures of rats in livetraps is tricky. This is a kiore.

Right now I just have a lot of home video, but ultimately this work should provide insights into ecological theory – for example, the ways in which interference competition affects niche space occupancy at individual and species levels. It should also have applied applications for invasive species management. New Zealand, like many oceanic islands, is in the position of having no native terrestrial mammals, and thus can manage invasive mammals, should they choose to do so, in relatively straightforward and robust ways. However, elsewhere management must avoid harming native mammal species. Triaging of the system, making adjustments to maximise the chances of catching the individuals with the greatest potential to cause harm, would be the most cost-effective way forward if eradication is not possible or desirable. And if eradication is the goal, then you need to know there aren’t individuals that will avoid all control mechanisms. Either way, identifying those individuals with a ‘troublemaking personality’ (as any press release might say but any scientific paper would not) is key.