Category: wildlife ecology

1080 reasons for optimism
Photo overlooking Mount Summers (Jan 2022). Image by Chida Chapagain.

It’s good to be optimistic. I have always been hopeful about the future. I lived the first 11 years of my life in a refugee camp. Times were tough, but I knew things could only get better. Even as a child, I knew there was more to this world than what I had experienced.

Fast forwards a couple of years, and my family and I are living in New Zealand, happier than ever. The first 11 years in Nepal, compared to my last 11 years here in New Zealand, have been extremely different. My life changed for the better.

Sometimes I wonder what would have happened if my family had moved to America or Australia instead of New Zealand. I often catch myself saying, “maybe my life would have been even better?” Optimism combined with curiosity can be a powerful motivator, leading us to explore the unknown. But we must be realistic with our expectations. Just because we are optimistic about the unknown doesn’t mean it must be true. There will always be challenges and limitations. Nothing is, or will ever be, perfect.

The same applies to alternative pest control methods being developed in New Zealand. The pest control toxin 1080 has its concerns, as do alternative methods that have been or are being developed. 1080 is a fully developed method that has been repeatedly shown to control introduced pest mammal populations on a large scale.

The common brushtail possum (Sept 2010). Photo by Daniela Parra from Flickr.

While it may not be perfect, it is widely recognised among scientists and conservationists that 1080 is currently the best tool we have for pest control. The use of 1080 is essential in protecting our native flora and fauna. However, we should always be looking to make improvements, but until such progress is made, the use of 1080 must continue. Perhaps you’ve read other things about 1080 and don’t agree. Allow me to explain.

Bruce Warburton, Penny Fisher, Brian Hopkins, Graham Nugent, and Phil E. Cowan of Manakai Whenua Lanacare Reserach, along with James Ross of Lincoln University, outline the major areas of concern raised by 1080 and summarise the changes that have been made to the use of 1080 to address these concerns.

The main four concerns related to the use of 1080 have been:
1. the potential environmental and human health risks,
2. the limited control over where the bait lands when applied aerially,
3. the lack of species selectivity, and
4. the animal welfare impact on target and non-target species.
They explore the impacts of 1080 use for conservation and bovine tuberculosis (TB) control. They then summarise alternative toxicants and methods for mammal pest control being investigated in New Zealand. Then they address to what extent these alternative methods might be able to address the concerns raised by 1080 opponents. This article may alter your views on 1080.

1080 is the current best tool we have for our unique fauna!

Sodium fluoroacetate (1080) has been a recognised pesticide since the early 1940s. 1080 is most frequently mixed into cereal baits for possum and ship rat control. New Zealand is the world’s largest user of 1080. The extensive use of 1080 in New Zealand is made possible by our unique fauna, where we have 35 introduced mammal species and only two native terrestrial mammals (both bats).

Introduced mammals, such as rats, possums, and stoats, are widespread and have significant impacts on native biodiversity and/or agricultural production. They continue to damage and threaten native and endemic species at unacceptably high rates.

Māori believe ‘failure to act falls short of our responsibilities to our ancestors, and future generations’. Fortunately, 1080 is a very efficient method for pest control. Monitoring by the Department of Conservation (DOC) before and after aerial 1080 operations targeting possums, rodents, and stoats has repeatedly shown consistent benefits for nesting success in kiwi, kea, kaka, whio, pīwauwau, mohua, and tītitipounamu. O’Donnell and Hoare in 2012 found native bird populations to have doubled after more than 20 years of sustained predator control.

North Island Saddleback (Oct 2021). Photo by Geoff Mckay from Flickr.

Are the ‘concerns’ about 1080 fact or evidence-based?

There are concerns and opposition to the use of 1080. Some are evidence-based. 1080 does kill non-target species. According to Dave Hansford, about 12% of radio-tagged kea died after aerial 1080 operations. In 1970, there was a ministerial review of the properties, effectiveness, and regulatory control of 1080. The review supported the use of 1080 but also recommended areas for improvement. Most of these recommendations were implemented, but opposition to its use remained.

In 2006, there was another formal assessment of 1080. Once again, the use of 1080 was permitted. 1080 opponents were still outraged. This triggered another investigation by the Parliamentary Commissioner for the Environment (PCE), who is tasked with providing independent advice to the government. The PCE concluded that “not only should the use of 1080 continue, but that we should use more of it.” Justified concerns about 1080 have been thoroughly reviewed many times, and these reviews have refined the ways in which 1080 is used safely to benefit the NZ environment. The remaining strong opposition to 1080 use by some New Zealanders has required that a lot of time and money being spent on developing, testing, and registering alternatives to 1080.

What are these alternative pest control methods?

There are many alternative methods for pest control. However, many of these are not feasible for our unique situation. For example, shooting is not a viable method for small mammals like mice and rats, and it is too expensive to apply on a large scale. Trapping, similarly is not cost-effective for large-scale operations, especially in the more remote, mountainous parts of New Zealand. Although these methods can complement 1080, they cannot achieve the levels required for effective large-scale conservation. New toxins, including zinc phosphide, sodium nitrate, coumatetrayl, and diphacinone, have also been registered for use. However, none have been developed for aerial use.

Genetic methods have the potential to drastically reduce the population of mammalian pests. There is a lot of attention on “gene drives”, which are engineered using the CRISPR/Cas9 genome editing technology. The gene drive DNA sequence, typically for reduced fertility, is then interwoven into the genome of an individual organism of the pest species, and every offspring of that individual inherits this modified DNA. One individual with this deleterious gene could potentially lead to complete eradication. This is the most promising alternative to 1080 in terms of cost and efficacy. There is, however, be significant scientific and public scrutiny to be done on this method.

In the meantime, our birds are continuing to be eaten by pest mammals.

My final thoughts

Having lived in both Nepal and New Zealand, I have been able to witness many beautiful birds. Nepal is home to the Himalayan Monal, which is my favourite. I vividly remember chasing this colourful bird around as a child. New Zealand is also home to many beautiful birds. We cherish these birds; they are part of us. However, today, many of them face the risk of extinction.

I am not an expert in pest control, but, I understand that without pest control, conservation programmes would fail. Reviews after reviews have shown that 1080 is the best current pest control method we have for introduced predatory mammals (possums, mice, rats, stoats, weasels) in New Zealand. Until we have better options, we need to continue using the best tools because our endangered endemic species cannot wait. We are lucky to have a pest control method that has proven to be so effective. It’s good to be optimistic.

The author Chida Chapagain 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.
October 3, 2022
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
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
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