Category: student blog

Fishing for possum DNA

When I was a child, I was fixated on animals. In fact, 5-year-old me would go around telling all the primary school mums that I wanted to be a Palaeontologist. This was often met with some strange looks, quite possibly because they didn’t even know what a Palaeontologist was themselves. Since then, I have been less focused on digging up dead animals and more interested in protecting the ones that are still alive.

In New Zealand, tourism and agriculture are arguably the biggest money-maker industries. People flood from overseas to check out the clean green image being advertised in their home countries for themselves. The ‘Great Walks’ lead tourists through the rugged bush that New Zealand has to offer. Along the way they might even see some of our diverse flora and fauna, of which most can not be found elsewhere on Earth.

On the other hand, the dairy, sheep and beef industries in New Zealand, earn large amounts of overseas revenue. This all started when Samuel Marsden introduced shorthorn dairy cattle to New Zealand from New South Wales and the rest is history.

https://www.australiangeographic.com.au/topics/wildlife/2017/04/killer-possums/

This brings me to the devious, but very cute looking, Brushtail Possum, Trichosurus vulpecula. In Australia, the Brushtail Possum is a protected species. In New Zealand they are a serious threat to our homegrown species. Possums compete with our native bird species for food and inhabit the same areas. These fluff balls are omnivores. In addition to eating the leaves off trees, they rob the nests of birds and eat the chicks and eggs.

Bovine tuberculosis is a disease that affects many farm animal species. Possums are the biggest carriers of tuberculosis and can infect herds of dairy cows, causing serious illness to the animals and a large vet bill for the farmer. Due to these factors, New Zealand tries incredibly hard to get rid of these furry mammals. One important thing that we need to know is where these possums are present and and in what numbers. For a nocturnal and relatively cryptid species, this is a lot harder to do than simply call a roll!

The use of trace DNA to monitor animals, such as possums, is a relatively new concept. However, a trial was held in Canterbury where researchers collected DNA from saliva left on WaxTags and Chewcards to determine the number of possums in an area and check whether these individuals were Tuberculosis carriers. From the initial field study, it was found that multiple possums would bite the WaxTag and Chew cards which made it difficult for the lab team to isolate certain animals. A new device to collect data was needed.

A mechanical collection device was created which would remove the bait after one animal had bitten into it, which protected the saliva and therefore the individual DNA could be distinguished. The device was a bit like a fishing line, catching its prey and then reeling in the DNA! Researchers found that the mechanical device allowed the DNA to be collected and more easily sequenced. They also found that the genetic material was more easily recovered from covered WaxTags than on the uncovered WaxTags.

Mechanical device created to protect DNA sample on the WaxTag.
Image from: A New Non-Invasive Method for Collecting DNA From Small Mammals in the Field, and Its Application in Simultaneous Vector and Disease Monitoring in Brushtail Possums

Cameras used in the field trials picked up that the possums interacted with the new WaxTags, and 87% of the devices were triggered after the first interaction. This is a positive point because in order for a monitoring device to be useful, the target has to interact with it.

This new way of collecting trace DNA samples was a success. DNA from Brushtail Possums was able to be amplified for genetic identification and was able to detect if diseases were present. The combination of the device being interesting enough for the targets to interact with, and the subsequent DNA extracted being protected until collection, means that it is ever more likely that technology like this can be used for other pest species to determine their disease risk.

The current study is the first to collect trace amounts of possum DNA and keep it protected from the elements until genetic analysis has taken place. This is a pretty big step for DNA collection methods. However, transmission of infectious diseases by vectors, such as possums, is density dependant. More collection devices need to be installed in these areas being studied to create ‘encounter’ history for individuals to determine population density and to calculate the likeliness for for transmission of these vector carried diseases.

This research suggests that there are new ways for non-invasive monitoring pest populations. The road to New Zealand being predator free by 2050 is a long one, but is shortened by the impressive new technologies being developed in the pest management space. This technology is key for determining the populations of pests in their area and how likely their livestock are to contracting devastating diseases such as Bovine Tuberculosis.

Dealing with pests may not be the most fun thing to do week to week, however, determining where populations are and where the risks lie can help experienced personal to more effectively manage pest populations and get New Zealand back to where we should be, mammal predator free.

This article was prepared by postgraduate student Rebecca Anderson as part of the ECOL608 Research Methods in Ecology course.

Emami-Khoyi A, Agnew TW, Adair MG, Murphy EC, Benmazouz I, Monsanto DM, Parbhu SP, Main DC, Le Roux R, Golla TR, Schnelle C, Alizadeh H, Csányi S, Heltai M, Jansen van Vuuren B, Paterson AM, Teske PR and Ross JG (2021) A New Non-invasive Method for Collecting DNA From Small Mammals in the Field, and Its Application in Simultaneous Vector and Disease Monitoring in Brushtail Possums. Front. Environ. Sci. 9:701033. https://doi.org/10.3389/fenvs.2021.701033

September 19, 2022
Māori environmental values and assessments of ecological effects

A resprouted pūriri tree. Photo/Paula Godfrey, December 2021

I never imagined as a small child that growing up I’d be an ecologist, deciding the fate of trees we drove past, and maybe one day, the very trees I climbed. One of my favorite trees is a silver ponga (Cyathea dealbata) near our whare (house). The photograph below shows me as an 8-year-old sitting in my ponga tree. For several months a year, I couldn’t climb the ponga while it grew its new fronds. We were strictly not allowed to cause any tree to die without good reason and a blessing from Papatūānuku. As a child, my whānau and I spent a lot of time up trees and exploring the the lush bush of north Auckland.

Sitting in my favourite ponga, 2002.

As an ecologist working in botany, I get asked all the time what my favourite tree/plant is, and the answer changes depending on what’s looking particularly beautiful that week. Are the kōwhai (Sophora spp.) flowering? Have the kauri (Agathis australis) got new growth? Have the māhoe (Melicytus ramiflorus) produced another bumper crop? These are the factors that influence my answer.

Take for example the pūriri tree (Vitex lucens). Pūriri has significant ecological value in its own right and is often my favorite tree. It produces flowers almost all-year round for tuī to feed on. It allows kereru to eat its berries and it even hosts NZ’s largest moth species (the massive green pūriri moths, Aenetus virescens).

These trees are impossible to age, as the old specimens have hollow trunks and twisted hard wood, making traditional ageing techniques very difficult. It’s thought that pūriri are the longest living plant in NZ. As part of pūriri tree’s life cycle, they typically start looking sick, fall over and ‘resprout’ by producing roots along their trunk that sink into the ground. By doing so they form large areas of canopy from a single trunk, as now their trunk is prostrate. The photo above shows a pūriri tree which has been cut down and resprouted. The hollow trunk is visible on the right of the photo.

Pūriri holds ecological values but also holds significant tangata whenua values. For me, as a Ngāpuhi (Northland iwi within the pūriri distribution area), I have a strong emotional connection to pūriri that is intertwined with its ecological value. How can that be?

Well, pūriri is used as an infusion to wash the bodies of our tūpāpaku (deceased) and adorned with pūriri leaves as they decomposed. The bones are later gathered up and scraped clean, then placed within the pūriri tree in a kete. These days, we simply adorn our tūpāpaku with pūriri and lay them to rest within Papatūānuku. This is what my brothers, myself and Māmā did with our Pāpā. Learn more about this practice here.

Cutting down a pūriri tree is like digging up a church cemetery without exhuming the bodies first, and in many cases, even today, this would happen without notification to the tīpuna (ancestors) of those who lay there.

Laying Pāpa to rest. I am middle left. Note the pūriri leaves surrounding the body. Photo/ John Malcom, 2006.

The issue of Māori values and the environment was brought to media attention (again) last year with the new marina works in Pūtiki bay, Waiheke Island, and the 2020 protests over Ihumātao, the historic stonefields in Auckland en-route to become a major housing development. Although Ihumātao was not a specific environmental issue, environment and ecology is undeniably intertwined.

As an ecologist working for a private consultancy, or even a government organisation, such as Waka Kotahi, or a local council, you’ll come across new developments (or redevelopments) seeking resource consent. To gain resource consent you need to demonstrate as an ecologist that the environment is not going to be degraded, and that post-development you’ll end up with a ‘net ecological gain’. This is called an Assessment of Environmental Effects (AEE).

There is a recommendation to include tangata whenua rights in AEE’s (as per the Section 8 of the Resource Management Act 1991). In practice they are kept as separate documents, with no cross-over between cultural effects and environmental effects. How can AEE’s integrate tangata whenua rights as part of an ecological assessment and fulfil the principles of the Treaty of Waitangi?

A sign at the Ihumātao protests. Photo/ RNZ, Dan Cook, March 2019.

In 1998 Stuart Waddel thought about the same question. He undertook a study to recognise the indigenous rights in AEE’s and how to integrate them. He found that applicants for resource consents have no statutory requirements to contact tangata whenua when proposing a new development, it is only ‘good practice’ to do so. The AEE’s are used to inform the consentingauthority (local councils) on the potential effects that the activity will have on the environment. Therefore, the contact with tangata whenua needs to be prior to the AEE being produced, not after. One good example of intergrating tangata whenua into an AEE is on the MacKays to Peka Peka Project by NZTA.

Recognition of kaitiakitanga (guardianship) in the AEE’s is when it comes to identification of potential environmental impacts as important for achieving better environmental outcomes for all. The environmental values are interconnected with the mauri (essence/life force) of the area, and links spiritual, genealogical, cultural and physical values. Recognition of kaitiakitanga in AEE’s (because it’s respected within tikanga Māori (cultural practice)), cannot be defined by local councils or government as that would mean they are speaking for kaitiakitanga, which is reserved for tangata whenua to speak to.

Waddel noted that Pākehā and Māori have long held differing views on the values of our environment, which has lead to contentious issues throughout the colonising history of NZ. Māori value the earth as a precious gift and follow strict rules on kaitiakitanga through kaitiaki (looking after) our environment in order to receive the life giving resources it provides. Māori also value different food sources to Pākehā, such as kahikatea berries. Pākehā tend to view the whenua (land) as a resource ripe for exploitation.
Ensuring that the proposed development area will be able to be sustainably used for future generations and for mahinga kai (food gathering) is a meaningful environmental outcome that demonstrates that the environment will retain its mauri.

Shaking the kahikatea berries down for eating, 2005.

It is more important than ever to carry out pre-project consultation with tangata whenua groups (iwi, hapu, rūnanga) and listen to what they have to say. The real environmental outcomes are achieved when the korero (conversation) is received by the development team with a learning mindset, and tangata whenua recommendations are implemented early in the project. If you’re a bit stuck on where to start, the Bay of Plenty Regional Council has a good resource for iwi engagement on their website.

Iwi engagement in AEE’s are beneficial for all. If AEE’s are done right, those hundred year-old pūriri trees would be here to stay and not replaced with a car park. If cultural considerations were implemented decades ago, we would have a much more natural environment, greater climate change resilience and many more trees to climb in our neighbourhoods.

If you want to gain a deeper understanding of kaitiakitanga, I highly recommend reading the book Braiding Sweetgrass by Robin Wall Kimmerer who shares a Native American perspective which is similar to te ao Māori worldviews.

Citation: Waddel, S. R. (1998). Restoring Kaitiakitanga: evaluating the recognition of indigenous rights in assessment of environmental effects (Doctoral dissertation, Lincoln University).

The author Paula Godfrey is a postgraduate student in the Postgraduate Diploma in Applied Science taught at Lincoln University. This article was written as an assessment for ECOL 608 Research Methods in Ecology.

August 22, 2022
Nosy predators check out the competition

Growing up in New Zealand, I had a great passion for animals. Viewing everything through a child’s eyes, I believed that all wildlife should be free to thrive anywhere they wanted. Today I see the realities of the world were all animals are cherished, but some are out of place and others are vulnerable. I am not alone in realising the endangerment and damage that pest species can cause to our native species. This awareness has me seeking to understand the appropriateness of eliminating certain species from particular locations in order to protect others.

The flora and fauna within New Zealand are some of the most remarkable in the world. A large majority of the animals and plants (and fungi) are endemic, or unique, to New Zealand. Over the years, many species have been introduced to New Zealand, such as ferrets, stoats, hedgehogs and ship rats, that have put these unique animals and plants at risk. It has become vital that monitoring and control of these predators is implemented to allow our native species a greater chance of survival.

Research to improve strategies and techniques to monitor and remove these predator species has been underway for many years now. One method used to monitor these predators is through deploying food-based lures that attract the target animals to traps or cameras. This allows for observations to be made in order to determine the density of these species in the surrounding area, as well as to increase the chances of trapping and removing these animals.

One way to attract these predators is to use odours from more dominant predators to attract the target species to the traps or cameras. This technique is based on the observation that mammals, like stoats and rats, use scent as their primary sense to forage for food and detect dominant species (higher ranking species than themselves). Dominant species directly influence the behaviour of mesopredators (mid ranking predators) by either attracting them or repelling them away from the odour. A dominant predator’s odour may provoke the subordinate (lower ranking predator) into preforming eavesdropping behaviour. This behaviour is used by species to inspect the location where the dominant predator has roamed. If the location is good enough for the big, tough predator then maybe it is a good place for the subordinate as well.

Researchers from Lincoln University, University of Auckland and Landcare Research chose to test ferret odour verses fresh rabbit meat (a traditional lure) for stoats, hedgehogs and ship rats. This study took place at Toronui station, a 1500 hectare sheep and beef farm located in Northern Hawkes Bay. It lasted for 64 days trial.

From left to right; Stoat (Mustela erminea), Hedgehog (Erinaceus europaeus), Ship Rat (Rattus rattus) and Ferret (Mustela putorius furo), all mammalian predators introduced to New Zealand. Charlie Marshall, (CC BY 2.0), https://www.flickr.com/photos/100915417@N07/49407663736; Jesus Duarte, (CC BY-NC-ND 2.0), https://www.flickr.com/photos/26795194@N00/8897432606; Amanda and William Explore, (CC BY-NC 4.0), https://www.inaturalist.org/observations/120567285; Max Moreau, (CC BY 2.0), https://www.flickr.com/photos/9426349@N07/6085681724.

The results from this trial confirmed that the ferret odour was the best for attraction, at least for stoats and hedgehogs, while rats avoided the ferret odour. Other studies have also found that rats avoid fresh odours. Stoats showed the strongest attraction to the ferret odour, with double the number of stoats being observed at the monitoring stations compared to fresh rabbit meat. These results can lead to exciting new possibilities to improve the monitoring and management of these species, especially in places where they are predicted to be rare.

One surprising result that was found was that the population of stoats at Toronui station before the study began was estimated to be rare. After the study was completed, the stoat population was predicted to be widespread. This makes you wonder just how underestimated the population of stoats in New Zealand really is.

Studies like this are important as New Zealand. With very limited native mammals, the native species, such as birds and insects, within New Zealand have had no need to adapt to mammalian predators. As a consequence when predator mammals were introduced into New Zealand they caused devastating damage to the endemic species.

Ferret odour lures were found to last longer than the fresh rabbit meat lures. This means that the ferret odour lures can be left out in the field for a longer period of time and still work just as well. Rabbit meat lures become ineffective faster leading to underestimates of pest populations.

The finding of the effectiveness of ferret odour as an attractant, especially in stoats, introduces a new tool and opportunity for pest management and conservation. It opens up many paths for future research to develop and learn more about this type of monitoring and the positive effects that it could have on our native species. More recent work has reported similar outcomes.

Mammalian predators are a major threat to the unique biodiversity that we have in New Zealand. New discoveries, such as the use of dominant predator odour in predator removal, gives me hope that there is a future for our taonga, native species.

The author Stacey Lewthwaite is a postgraduate student in the Master of International Nature Conservation taught at Lincoln University. This article was written as an assessment for ECOL 608 Research Methods in Ecology.

Garvey, P. M., Glen, A. S., Clout, M. N., Wyse, S. V., Nichols, M., & Pech, R. P. (2017). Exploiting interspecific olfactory communication to monitor predators. Ecological Applications, 27(2), 389-402.

August 18, 2022
Can mushrooms save our planet from burping cows?

Ever since I was a small child, I have listened to people talk about global warming and climate change. Back then I had no idea what it meant. Was our planet going to catch on fire? Were we all going to die? And why did no one seem to agree if it was fact or fiction?

I come from a family of old school sheep and beef farmers that believed it to be a myth, or at least an over-exaggerations by scientists. As I grew up, I became increasingly more inquisitive, always asking how could something as large as our planet be warming? And what could be the cause?

Burning earth globe west hemisphere. By Boris Ryaposov. © Adobe Stock #45170848, used with license

Many of my questions were left unanswered until I started high school and discovered science. Straight away I fell in love with its explanations for how everything functioned. Everything from the stars in the sky right down to the soil beneath our feet (and even further down to the centre of the earth).

Global warming quickly became a topic that piqued my interest. The more I learnt, the more obvious it became that it was a very real, very serious problem. What exactly is global warming? Thankfully, the planet isn’t going to literally catch on fire like I once thought (although fires will be more likely). The temperature of our planet is slowly increasing each year due to ‘dirty industries‘ pumping pollutants, called greenhouse gases (GHGs), into the atmosphere.

These gasses end up trapping heat from the sun, rather than it being reflected back into space. This heat warms the atmosphere, resulting in extreme weather events becoming more frequent . This means more forest fires, droughts, floods and heatwaves, which combined have disastrous effects on the environment and negatively affect many peoples’ lives.

Methane emissions! 牛のゲップ、メタンガス排出のイラスト. By MAYUK0. © Adobe Stock #488498751, used with license.

Studying environmental science at university has taught me all of the main contributors to this problem. A major issue for New Zealand (NZ) is the gas methane. Methane makes up the majority of NZ’s agricultural GHG emissions, and it often comes from farm animals, such as sheep and cows. These animals produce methane during their digestive process and release it into the air by burping! Scientists have estimated that 40% of the total warming effect generated by human activities is due to methane.

Under the Climate Change Act, NZ must reduce methane emissions from agriculture by 10% by 2030, and within the range of 24-47% reduction by 2050 (NIWA). Hence finding methods to reduce the amount of methane produced by animals is particularly important.

The paper by K.T. Rangubhet and colleagues in the Journal Animal Feed Science and Technology found that by adding spent mushroom substrate (SMS) to cow food, that their methane emissions were significantly reduced.

Mushroom substrate refers to the waste generated from mushroom production and is usually found in abundance after a mushroom harvesting period. The chemical composition of the mushrooms affects an animal’s fermentation and ecology. A useful byproduct of this is reduced amounts of methane burped into the atmosphere. Applying SMS to the feed of dairy cows could reduce the amount of emissions that animals contribute to greenhouse gases.

Fungi – an image by Adrian Paterson

Adding spent mushroom substrate uses diet and nutrition as a method to reduce GHG emissions throughout NZ. It is an approach that could allow our country to achieve the reduction goal set by the climate change act. Since this is in the next 8 years, SMS may be able to help NZ achieve these goals, especially as it is cost-effective and easy to apply. Other approaches are herd management, where animal breeds are selected that can utilise food more efficiently, and emit less methane. The strategy also includes reducing the number of unproductive animals in a herd to improve profitability.

If these methods continue to show promise by substantially reducing methane emissions from dairy cows, this could be applied to farms throughout NZ. SMS could make a real difference to this country’s effort to prevent climate change due to GHG. This could then be part of a global solution to help to mitigate climate change and slow down our planet’s increasing temperature.

The author Polly Cavanagh is a postgraduate student in the Master of Science -Environmental Science taught at Lincoln University. This article was written as an assessment for ECOL 608 Research Methods in Ecology.

August 9, 2022
The spitfire: a sure-fire way to eradicate stoats?

Stoat! Look out, the RAF (Really Awesome Field-research) is coming! Photo CC BY-NC 2.0 Stuart Smith, Flickr

Stoats, weasels and ferrets: the terrifying trio. If New Zealand’s native birds could speak, I’m sure that’s how they would refer to them as they swap stories of escape and near misses. Widespread, wily and lethal, the stoat is considered the greatest threat to the survival of many endangered and threatened native birds on the mainland, such as the takahe, orange-fronted parakeet, and Leonardo DiCaprio’s favourite, the kakī (black stilt).

Here are the cold, hard facts. Humans introduced stoats from Europe to control rabbits in the 1880’s, against the advice of ecologists at the time. They have since run rampant over our native bird species, throwing many populations into a drastic decline. Like clever little kleptomaniacs, they sleep on beds of feathers stolen from our most treasured and rare birds.

We must eradicate stoats from areas of New Zealand if we are to have an extant bird as our national icon. The prevailing question is, how?

Photo CC BY-NC-ND 2.0 Shellie Evans, Flickr

Never fear, the Spitfire is here! Unless you are a stoat then, yes, be afraid. The Spitfire is a re-setting toxin delivery device which was trialled in the Blue Mountains of Otago in 2013. 65 Spitfire devices were set up for approximately six weeks. Each device was capable of delivering 100 lethal doses of the stoat killing toxin PAPP (para-aminopropiophenone).

The stoat population was monitored in the area during this time using trail cameras and tracking tunnels in order to measure the Spitfire’s effects.

The project was carried out by Elaine Murphy, Tim Sjoberg and James Ross from Lincoln University, along with researchers from Wildlands, the Department of Conservation and Connovation. They found that the Spitfire knocked down 62% of the stoat population in the trial area.

The Spitfire is a very picky individual, only delivering the lethal dose of poison to a suitor of the right body size and shape. The device is able to do this due to its dual sensors. Cameras trained on the Spitfire devices during the trial in Otago recorded no instances of non-target species, such as rifleman, receiving any of the poison. PAPP has been registered for use in stoat control since 2011, but is mostly available for use in fresh meat lures, which are labour intensive to produce and expire quickly.

The 2013 trial was a success for the Spitfire and PAPP, but it was not without it’s issues. It was a trial after all! Many of the devices malfunctioned before the end of the six week trial due to design faults in weather proofing and circuitry. The conclusion was that the Spitfire showed promise, but lacked in stamina and sturdiness.

Kereru in Kawakawa, Photo CC BY 2.0 Geoff McKay, Flickr

All was not lost! In 2016 the New Zealand Government announced its goal to become predator (rats, mustelids and possums) free by 2050, which led to a funding initiative called ‘Products to Purchase‘ from PF2050 Ltd. Five products were selected, based on their expected contribution to the cause, to receive funding to fast track their development to a marketable level.

In 2019, the first five successful applicants were named, and who should be among them but our voracious Spitfire. A Tauranga based start-up called Envico Technologies Ltd (ECT) went back to the drawing board with the device. They re-engineered and re-invigorated the design and produced a prototype they could now commercialise, all with the help of the funding from PF2050 Ltd.

The Spitfire was back in the game, with the new design finalised in 2020. The latest model promises a longer lifespan of one year, during which no maintenance or refills are required. It’s widely known that the main cost in stoat control is in the field hours with bait station and trap operations, so this hands-free option is looking like an economical as well as an effective choice.

Also on the toolbelt of the new Spitfire model is a bluetooth data logger, which records the date and time of trigger events. ECT envisions this feature being highly beneficial for monitoring pest populations and assisting with re-invasion events in eradicated areas. Because of it’s long field life, the Spitfire becomes an attractive option for use in more remote areas where previously the only viable option has been aerial 1080 drops. If you have a ‘Ban 1080’ bumper sticker, this product may be for you.

Brushtail possum and her joey at Tārerekautuku Yarrs Lagoon, Photo Katherine Turton.

Just when you think it can’t get any better, a distinct advantage of the Spitfire is that there are few issues with alternative food sources or bait shyness. Stoats don’t have to bite, pull, stand on a treadle, or count backwards from 100 to receive a lethal dose. They are simply drawn in by an automatic lure dispenser that keeps a delicious mayonnaise paste coming all year-round.

The Spitfire is an intellectual. It has smart capacitive sensors that can detect and measure anything that is conductive. It can tell the difference between the long sausage body of a stoat and a little compact rifleman, preventing our inquisitive native species from receiving the toxin. When the Spitfire senses a stoat it launches a lethal splurge of toxin onto the abdomen, after which the animals are instinctually driven to groom off the mess.

ECT joined forces with the Department of Conservation and Boffa Miskell to conduct field trials from 2020-2022. Alongside the stoat design, a model specifically for our Australian foes, the brushtail possum, was also trialled using a Diphacinone and Cholicalciferol toxin instead of PAPP.

Field trials are about to conclude for the Spitfire and ECT are expecting to roll out the finished product at $200 a piece. There is also talk that a rat specific Spitfire is now in the works! This innovative technology is paving the way for more effective pest control not just here in New Zealand but worldwide. Conservation groups get your wallets ready and watch this space!

For more information, see the article on the Sptifire trial in Otago and follow ECT to keep up with their latest technological solutions for conservation!

This article was prepared by postgraduate student Katherine Turton as part of the ECOL 608 Research Methods in Ecology course in her Master of Pest Management degree.

August 1, 2022
Blow-torching plants for hot evolutionary insights into flammability

Who would have thought that it is possible to get funding to torch dried plants on a grill, for science! The results are now in a scientific journal, contributing insights regarding the evolution of flammability in plants.

My 8-year-old self would have been delighted, that is for sure. Then I was already very interested in biology. I also had some ‘slightly’ pyromaniac tendencies. I conducted my own ‘research’ on the flammability of various household materials, such as cardboard, candles and scrap wood from my dad’s workshop in the basement.

My parents were probably a little too tolerant in this regard. They provided me with a relatively safe ‘lab’ environment that basically consisted of an inflammable tray, made of aluminium. This I could deploy in the garden to conduct my rather opportunistic experiments. My parents watched cautiously with a bucket of water in reach.

Luckily, everything turned out well, I did not burn down our house or anything of significance and instead grew up to focus on Biodiversity, Ecology and now Nature Conservation during my time at school and university. The only relic of my childhood experiments is a propensity to seek out excuses to (safely) ignite a campfire while hiking, to hone my caveman skills and to ‘impress’ my friends.

Dracophyllum rosmarinifolium, the inaka or common grass tree, Photo CC0 1.0 by Leon Billows, iNaturalist NZ

This brings us to the recent publication of Xinglei Cui et al., that was published earlier this year in Forest Ecosystems. Xinglei is a former PhD student on plant flammability at Lincoln University – now working at Sichuan Agricultural University, in Chengdu, China. He worked in collaboration with other researchers from China and New Zealand, among them LU’s Adrian Paterson, Kate Marshall and Tim Curran.

Xinglei wanted to solve the question of whether the presence of different environmental conditions (for example altitude above sea level) could explain differences in the flammability among individuals of the common grass tree or inaka (Dracophyllum rosmarinifolium). This plant was chosen since it occurs throughout the South Island and can live in very different habitats, from rocky slopes to plateaus and valley floors. Inaka also shows diverse shapes and sizes – a lot of variability among the same species.

Previous research, mostly focused on relating flammability of plants to fire frequency in their natural range, showed that species like gorse become more flammable when there are more fires. This has inspired macabre sounding hypotheses such as ‘kill thy neighbour’ or ‘born to burn’, and other good death metal sounding titles! While this might sound contradictory, some plants take an evolutionary advantage from being highly flammable, if being flammable kills your neighbours and provides open space for your pyromaniac offspring.

Coming back to our grass tree, we are not sure how flammability evolves without the regular presence of wildfires, like in New Zealand. This question becomes especially relevant considering rising temperatures and weather that becomes more and more unstable through climate change. Areas of the world are now burning where fire used to be rare. Answering this question could help to understand where and why the risk of wildfires could be higher in regions of New Zealand that experience increasing periods of ‘wildfire weather’ conditions.

Grill similar to the one used for the project, Photo CC BY 2.0 by Liz West, Flickr

Photo CC BY-NC 2.0 by Duncan C, Flickr

To test this, the researchers had the chance to use a device that looks suspiciously like it could be used for a nice barbecue after finishing the scientific experiments. Not only does it feature a regular gas burner, but also an awe-inspiring blow torch, based on the design of an older publication and adapted to New Zealand safety standards by Sarah Wyse in 2016. Shoot samples from eight different South Island locations, each with different environmental and habitat conditions, were tested regarding their burning qualities. After 24 hours of air drying, they were preheated for 2 minutes before trying to set them on fire. Then, duration, temperatures and the amount of the plant that got burned in the process were measured – what a task!

Flammability among plants from the eight locations varied a lot, although every single sample caught fire. The sample from Mt Arthur in the north of the South Island was most flammable, while individuals from the Homer Tunnel in Fiordland were least flammable. However, the influence of the habitat conditions from those eight sampling conditions turned out not to be related to the flammability of the grass tree.

What do these results tell us about the evolution of flammability in the common grass tree, if environmental conditions don’t seem to have an effect on it? Xinglei and his colleagues concluded that flammability of this plant is more likely to be a by-product, an indirect result in the evolution of other characteristics of this plant, since it grows – in areas without a natural wild fire regime.

In any case, the authors highlight that it is important to continue this type of research to understand and manage the risk of wildfires in light of climate change. This may help us to understand where wildfires are likely to occur in New Zealand and to react and plan accordingly. Many further questions have to be solved. For example, is the current flammability of the grass tree passed directly on to the next generation and why are flammability traits so different among individuals of the same species.

There are many more projects to come and more importantly, many chances to safely live out your pyromaniac tendencies! I’m keen, and I have my own tray!

This article was prepared by postgraduate student Jan-Niklas Trei as part of the ECOL 608 Research Methods in Ecology course in her Master of International Nature Conservation degree.

July 31, 2022
Flooding causes greenhouse gas emissions to spike! …Liming to the rescue?

Climate change, greenhouse gas emissions, nitrate leaching… a climate crisis! With the frequency of how these phrases are used today, it does not require a vast imagination to connect the dots and find some sort of a global catastrophe lurking around the corner. And who could be blamed when just last year, the World Health Organisation labelled climate change as the “single biggest threat facing humanity”. They frequently used terms like ‘crisis’, ‘catastrophe’, and perhaps most daunting, ‘inevitable’ within their annual review.

While this is all clearly alarming, a big question that we must ask is how this will affect New Zealand?

Climate change has been felt throughout the world, and New Zealand is no exception. The current New Zealand government declared a climate emergency in 2020. While some may consider its declaration to be reactionary, it is nonetheless a powerful statement.

In the face of climate change, the single biggest challenge is how to sustainably and effectively reduce global greenhouse gas emissions. Everyone seems to be trying to find an answer while simultaneously passing the blame onto someone else. Delving into the rabbit hole of climate change mismanagement, I found a tangled mess of political bureaucracy, tied up with industrial and economic intrigue. But most importantly, I discerned that the question on how to best solve climate change is much too hard to answer within this short blog post.

Flooded pastureland

Since a significant proportion of greenhouse gas emissions is owed to increases in agriculture, reducing agricultural emissions can help alleviate this issue. Let’s look at one tiny corner of agriculture. As climate change triggers higher rainfall and more flooding events, an increase in nitrous oxide (N₂O) emissions will occur, due to the loss of oxygen in the soil.

N₂O has been estimated as having 300 times more global warming potential than carbon dioxide (CO₂), and yet has been largely ignored as a greenhouse gas. Agricultural soils, being highly fertile with a high nitrogen content, contribute massively to the amount of N₂O produced annually throughout the world. Understanding how to control and limit N₂O production from agricultural land could result in major reductions of greenhouse gas emissions globally each year.

With this in mind, researchers from the University of Copenhagen in Denmark and Lincoln University in New Zealand examined the relationship between flooding events and N₂O emissions on fertile farmland. The study occurred in Canterbury New Zealand and found periodic flooding resulted in greater N₂O emissions while the amount of gas released could be reduced if liming had occurred recently. Liming is the process where crushed limestone is applied as a soil additive to directly increase soil pH and occurs frequently throughout the world. The significance of this result is not be understated and results in at least two implications for the future of agriculture and climate change as a whole.

Drainage Ditches

Firstly, since flooding can cause N₂O production to spike, areas of high flooding risk in low lying areas should have reduced fertiliser inputs during wetter months to prevent N₂O from being produced. Secondly, regular liming of agricultural land, particularly before high rainfall events, could help maintain pH levels limiting N₂O production.

This research shows the importance of having good drainage in agricultural areas, but also represents concern for the future as high rainfall events become more common, particularly in wetter areas of New Zealand.

Are we going to experience greater N₂O emissions in the future as climate change results in more extreme weather events? Will liming be sufficient at reducing N₂O emissions from farmland? Research seems to always create more questions than answers, but as I said earlier, this is much too hard to answer in a blog post.

What can be concluded is that since N₂O emissions appears to reduce by regularly applying agricultural lime to farmland, this could allow New Zealand to lower its global climate change impact. But perhaps most importantly, it shows us that if we are going to solve the issue of climate change, proactive research followed by successful implementation is often the best answer.

For additional details regarding this article, please refer to the research paper below:
Flooding-induced N₂O emission bursts controlled by pH and nitrate in agricultural soils.

Hansen, M., Clough, T. J., & Elberling, B. (2014). Flooding-induced N2O emission bursts controlled by pH and nitrate in agricultural soils. Soil Biology and Biochemistry, 69, 17-24.

The author Cameron Hilliard is a postgraduate student in the Master of Science taught at Lincoln University. This article was written as an assessment for ECOL 608 Research Methods in Ecology.

July 27, 2022
Is your house cat a ‘super-predator’?

A bell on a collar is commonly used by cat owners to try to protect local wildlife. Or at least to avoid dead carcasses being presented inside the home. A study of domestic cat behaviour at the Ōruapaeroa/Travis Wetland, Christchurch, suggests that this approach may not be as effective as you might expect.

Collar-bell warning devices are likely to be largely ineffective at reducing hunting success. This conclusion was drawn after a 12-month study of 88 domestic cats living close to the 119 ha wetland reserve. This is consistent with most (but not all) similar New Zealand and overseas studies. An explanation for such a confounding outcome may be due to a cat’s tenacity and ability to easily learn to compensate for the bell. Couple this also with the likelihood that birds don’t necessarily associate a bell warning with danger.

Photo credit: CC BY-SA 2.0 Brandon O’Connor, Flickr

Cat night curfew, another wildlife protection strategy required of responsible owners in Australia and promoted in New Zealand, may even be counterproductive. Many of our native species of birds and reptiles are mostly active during daylight. They hunker down and hide during night hours.

Mice and rats prefer the evening for their foraging explorations. These rodents are invasive pests that do immeasurable damage to New Zealand natives species, including birds. Since cats, by cultural convention and scientific study, are known to prey on rodents, it might seem detrimental to lock them inside at night.

Travis Wetland, is the last large freshwater wetland in Christchurch and is home to 53 species of birds. It has an estimated diversity of 700-900 invertebrate (mainly insect) species, many endemic to New Zealand. The urban cat research project at the wetland site was conducted by masters student Shelley Morgan, from Lincoln University. The study concluded that house cats in urban settings, bordering sensitive nature reserves like Travis Wetlands, do roam and incorporate these wildlands into their home ranges. There they target mostly rodent pests, but sometimes more precious native animals, like lizards and birds. Cats with bells were not any less effective in bringing home prey!

On balance, you might think that domestic cats provide beneficial services to bird populations by controlling mice and rats. This view is widely debated, with some recent studies arguing that cat predation has an overwhelming negative impact on native wildlife especially in wetlands, braided rivers and along shorelines. Furthermore, it seems likely that just a few of the moggies are particularly troublesome. Some cats are ’super-predators’, exhibiting a high tendency towards hunting, often focusing on a favoured prey. It appears that this little clowder of cats may have a disproportionate impact on threatened native species. As confronting as these uncomfortable facts are, they need to be acknowledged and solutions sought.

Photo credit: CC BY-SA 2.0 Niels Hartvig, Flickr

New Zealand has one of the highest levels of cat ownership in the world, with over half of households supporting at least a single cat. The social benefit of pet ownership, and the passion that we hold for our cats, should not be underestimated. A social licence to restrict ownership or cat movements will be difficult to achieve. Nevertheless, almost certainly within the community of cat lovers will be a myriad of ideas for limiting the danger to treasured native species.

One option is to seek agreement for a suitably sized cat-free buffer zone between urban and nature reserves. Although a risk remains that the absence of domestic cats in a halo around a wetland reserve might just encourage remaining cats in the district to prowl further and expand their hunting range.

The Royal New Zealand Society for the Prevention of Cruelty to Animals (RSPCA NZ) classifies cats into companion, stray and feral types in a recently published white paper. The organisation acknowledges the impact of free roaming cats on native biodiversity, but stresses the need to protect cat welfare and manage them humanely. The RSPCS promotes the need for cat owner self reflection, community debate and appropriate council bylaws. In the meantime, if you suspect that your beloved companion is a ‘super-predator’, perhaps consider a ‘Birdsbesafe‘ collar cover. Unlike a bell, the ‘birdsbesafe’ collar offers a colourful warning of a cat’s presence and alerts prey with good colour vision (birds and lizards).

Morgan, S. A., Hansen, C. M., Ross, J. G., Hickling, G. J., Ogilvie, S. C., & Paterson, A. M. (2009). Urban cat (Felis catus) movement and predation activity associated with a wetland reserve in New Zealand. Wildlife Research, 36(7), 574-580. https://doi.org/10.1071/WR09023

This article was prepared by postgraduate student Andrew Wells as part of the ECOL 608 Research Methods in Ecology course in his Master of Pest Management degree.

July 25, 2022
Seduced by the Stoat Stench

As a child who was raised next to the ocean, I suppose it’s only fitting that the beach is my attractant. Something about the sand between my toes takes me back to when I was 6. My talents were at a peak as I managed to take the win in multiple sandcastle competitions. The sea gives me a sense of security and allows my mind to reset, clearing all worrying thoughts. And of course, it is the foundation behind most of my hobbies; fishing, diving, swimming (and sandcastle building). The beach has always been a part of my upbringing, a place where I enjoy the company of family and friends.

Beach Day – CC BY-NC-ND Image by Anna Meban

One of the things I found most interesting after a trip down to the beach was how my little jack russell paid far more interest in me when I returned home. Now maybe this had something to do with us neglecting to take him with us, but he would always sidle up to me, frantically sniffing and then stare at me longingly, as though I had betrayed him. He knew I’d made friends with a passing puppy on the beach and he knew that whoever had left these hairs entwined in my clothing was not him.

It’s important to remember that these attractants differ, especially when they include scents such as urine, scats and bedding odours. Yes, you read that right, these are the types of odours that Lincoln University’s Elaine Murphy and James Ross, along with their fellow colleagues, investigated in terms of the power of attraction in stoats (Mustela erminea). More specifically their study discussed whether body odours of reproductively fertile (oestrous) stoats have the potential to be used as lures for pest trapping.

Their study, published in the journal Animals, tested these lures in a series of lab and field trials. Lab trials were undertaken at Lincoln University and involved wild-caught stoats. The experiment was set out in a way where each odour sample was placed in a metal mesh tea ball, allowing stoats to smell but not interact. As well as this, a control sample was used, consisting of unscented Dacron, allowing stoats to choose between scented and unscented chambers.

The field trials differed slightly, with the lure stations providing a menu selection of stoat odours and more traditional lures consisting of hens eggs and dried rabbit meat. The field trials took place in a range of New Zealand’s well-known locations, Abel Tasman, Lake Rotoiti (Tasman) and the Coromandel.

Exploratory Stoat – CC BY 2.0 Charlie Marshall (Flickr)

This got me thinking about how important scents are as an attraction method for animals, even for humans themselves. It may be the scent of home-cooked meals in the kitchen. The strong scent of cologne as your crush walks by. The smell of salty air drawing me to the ocean and reminding me of home. Everyone has something they are attracted to but these things differ depending on the person… or species.

In Abel Tasman and Lake Rotoiti, the trials compared fertile female stoat bedding odours to a dried rabbit meat block formulation. In the Lake Rotoiti trials, they also tested a combination of both lures together. It was the Coromandel trial that grabbed my attention, as this focused on whether male odours had the same charm as females. The trial was divided into two stages, first the male stoat bedding odour was partnered with either dried rabbit or hen eggs, and second, the male bedding odour was trialled on its own.

The lab and field trials both showed very promising outcomes for the control of stoats. In the captive animal trials, stoats had greater interaction times with stoat odours than with the control dacron. Stoat odours were just as much preferred by stoats as the hen eggs and dried rabbit meat. Male odours were also equally effective attractants for both males and females showing interest in the scent of the opposite sex.

So what can we do with these alluring aromas?

Well, it is becoming increasingly more evident that food lures in the wild are not always the most effective way of targeting stoats when using kill traps and bait stations. Although these are the best techniques at the moment, conservation workers still struggle to catch stoats in many locations. Elaine and her colleagues mention how this is likely due to every individual having different preferences (basically a personality), as well as stoats being spoilt for choice in terms of food sources in certain areas.

With all pest control there will be some animals that manage to dodge the bullet. The use of odour as a lure adds another technique into the mix. This new tool may be just what we need to increase chances of stoat capture rates in areas where food is abundant.

Stinky Stoat – CC BY-SA 2.0 Airwolfhound (Flickr)

What’s even better is that, as stoat populations begin to decline, this scent lures method will only become more effective! As desperation sets in and survivors scramble to find mating opportunities, they will lead themselves right into their own funky smelling fate.

But wait, there’s more…

From the results gathered within this study, it is thought that these stinky stoat odours may have even more potential than just capturing stoats. In conjunction with traditional lures, these odours also captured the attention of ferrets and rats. With the looming deadline of ‘Predator free 2050‘, this research could be the next step in trying to reduce these sneaky (and stinky!) pests.

More research is now needed to figure out which chemicals are driving the attraction and how to produce these lures in a form that can be utilised nationwide, Elaine, James and their colleagues are on the trail of a breakthrough scent that has the potential to revolutionise predator trapping methods. Something to think about next time I’m at the beach.

The author Anna Meban is a postgraduate student in the Master of Science – Conservation and Ecology taught at Lincoln University. This article was written for an assessment for ECOL 608 Research Methods in Ecology.

April 18, 2022