Christmas is just around the corner and for many this means that it is time to head to the sea. Beach holidays have long been a tradition for kiwi summers. I was no different while growing up and through my adult life. We spent a lot of time at the little beach village of Kaka Point, at the far northern end of the Catlins, in South Otago.
Not a lot deterred us from hitting the waves. The weather could be a little iffy and the water a little cool but that didn’t matter. You might have a to share the surf with a few other hardy swimmers and the occasional seal but it was bliss. But now I find that I may have been sharing my waves with something slightly more sinister!
Marlene terrorises us by showing that these spiders are all over the world. No beach is safe! She does reassure us that these water arachnids only make up 0.3% of all spiders (although that still seems too many). She reviews the work that has been done to show how spiders, usually very terrestrial, can survive in such a damp environment.
Some have hairs that trap air bubbles around themselves, other can use webs to close off empty shells to keep the air in. Some can go into a coma where they reduce the amount of oxygen required. Inter-tidal species can run away from incoming tides. These traits allow spiders to exploit a habitat that would otherwise be forbidden for them.
The aquatic Dolomedes.
It’s all very fascinating. Spiders have had to change the way they eat, avoid predators, reproduce, move, accommodate extreme temperatures, and cope with water pressure. Marlene summarises the adaptations. It’s a great read.
However, spiders in the sea is not really what you want to think about when you are rushing into the waves, boggie-board in hand. It’s almost a Gollum moment (as the Nazgul fly over him he shouts in horror “Wraiths! Wraiths on wings!”)
“Spiders! Spiders under water!”
Have a great Christmas holiday at the beach!
Adrian Paterson is a lecturer in Pest-Management and Conservation at Lincoln University. He generally likes spiders, but only when he can see them!
Imagine the Canterbury Plains blanketed in tall trees interwoven with small hardwoods. This beautiful, unique landscape is then singed into dry grassland with the arrival of Māori. Continue to imagine European settlers introduce weedy exotics that infest the landscapes, once again modifying the region. Now, picture the current landscape – a monotonous cover of dairy farms. Which of these images would you think is best for our native and endemic species?
Prior to humans or today? (Think from an insect’s perspective)
The plains have been a dynamic landscape ever since humans stepped foot in our vulnerable country. They will continue to experience dramatic changes in the future with the ever growing population leading to climate change, urban expansion and agriculture intensification.
The 1940s saw the commencement of irrigation on the plains so that farmers could have a reliable water source to enhance the production of pasture and crops. Water facilitated the development of dairying from sheep farming, into the landscape we see today. Between 2002 and 2012, the Canterbury herd increased by 115%, accounting for 13.5% of the Aotearoa dairy herd.
These drastic landscape changes have been detrimental to many of our precious native species by creating unfavourable conditions and habitats, species such as the bellbird (Anthornis melanura) have suffered. Some species, such as paradise shelducks (Tadorna variegata), have exploded in population numbers due to the favorable wet conditions caused from irrigating.
Within the Canterbury Plains, less than 0.5% of this area is still the original remnant forest. Canterbury has been described as the most biological deprived and most modified environment in Aotearoa due to the intensification of agriculture. However, agriculture is a big portion of the country’s economy, bringing in approximately $10.6 billion (5%) of the country’s Gross Domestic Product (GDP).
The food and fiber sector are major employer, providing jobs to over 359,000 people. Not only does it feed New Zealanders, it is also a big player in the global food market. in order to come to terms with this environmental dilemma, farms need to incorporate more sustainable agricultural practices, to feed the world and to support biodiversity. Currently through education and awareness this is already becoming a point of discussion.
There has been a push to introduce native vegetation into farming systems. Several studies have examined the impacts of intensive dairy farming on soil health, vegetation, and life below ground. Farmers are now starting to see the benefits of even simple things, such as planting native vegetation. Such plantings not only positively impact farms, but also our are good for our native species, from small bugs to cryptic skinks and chatty birds.
Mike Bowie from Lincoln University, like me, grew up on a family farm, and went on to tertiary education in ecology. This brings a helpful perspective to topics around the interaction of agriculture and ecology. It led Bowie to check out the biodiversity in the Bankside dryland remnant that is surrounded by an intensive dairy farming landscape. The Bankside Scientific Reserve in a 2.6-hectare area established in 1969. Mike wanted to know how adjacent agricultural land impacts the soil composition and fauna in this reserve area.
Aerial photograph of the Bankside Scientific Reserve with kānuka and matagouri dotted throughout. (From Bowie et al., 2015)
In 1970, an initial vegetation survey was conducted by Molloy within the new reserve. Bowie’s survey in 2015 found that only 31% of plants that Molloy surveyed still remained and that 27 new exotic species were present. The fauna found in the remnant were different to that of the neighbouring agricultural land. Bowie discovered the presence of four native earthworm species along with six exotic species. The number of the exotic worm species decreased with distance into the reserve.
Bowie and his fellow researchers found 112 specimens of invertebrates, including many beetles as well as a significant native species, the ground weta! Soil pH, nitrate, and phosphate levels were all lower in the reserve compared to the surrounding paddocks.
These observations highlight the need to retain existing dryland remnants and to establish other reserves throughout the plains. A diverse landscape will support a diverse range of species. I think farmers and the community are now starting to see the value of incorporating native vegetation and agroecological principles into their system, such as mixed species pasture systems.
We don’t all need to put three hectares away into a reserve. Even small steps, such as planting a row of diverse natives along a fence line or waterway, will make a huge difference, if many farms join in.
One thing that is highlighted in this study is the need for continued maintenance of restoration and remnant projects. It is not a plant and leave situation (no pun was intended…). Weed and pest control should be continually applied in these areas to prevent exotic weeds and animals from becoming established and smothering and displacing the natives.
An example of this is in practice Te Ara Kakariki group that is establishing green dots (tiny native areas) from the Southern Alps to Lake Ellesmere/Te Waihora on private properties. This increases the connectivity of native planting, further increasing the power that these small areas can make overall. Animals and invertebrates will be able to spread throughout these dots and over the region.
Farming has transformed the landscape of the Canterbury Plains. Image from Adrian Paterson.
Farmers are becoming more aware of sustainable principles through education from organisations such as Te Ara Kakariki, DairyNZ, Landcare trust, and councils. Through education, ecology is becoming more interwoven into their practices. It will be a trick balancing the need for feeding the world and protecting the environment. Ecology is an excellent way to find this balance in agriculture, it can be adapted to any farming system to suit their needs and desires.
Mike wants to help bridge this gap, not only in this study, but also others that he has conducted throughout his time at Lincoln University. Mike has examined how native plantings encourage native and beneficial invertebrates on Canterbury dairy farms, plus many more. I too believe that ecology and agriculture can work together to create a more sustainable agriculture sector that can efficiently produce food and improve food security, whilst supporting the health of the soil, water and biodiversity.
This article was prepared by Master of Science postgraduate student Sam Fitzgerald as part of her ECOL608 Research Methods in Ecology course.
Hambach. You are in Germany right now, halfway between Cologne and the Belgian border. I’d like to warmly welcome you to the Hambach forest – an ancient forest that is dominated by oak and hornbeam, representing a rare forest type in modern Germany. The Hambach forest is the last remnant of a forest that ranged over wide flat plains since the end of the last ice age around 12,000 years ago. Regrettably, it has become famous for being gradually absorbed by a vast hole!
The Hambach forest used to range over an area of around 5 500 ha. During the past four decades, around 90 percent has already vanished. What remains today is not a normal forest anymore – idyllic, undisturbed, and peaceful. The forest is not only threatened by further sliding into the hole. In 2018, the Hambach forest also became the stage for one of the largest major police operations, owing to another curiosity about the Hambach forest: it is inhabited by people, living in tree houses. Occupying the forest, they want to protect what is left of it and demonstrate against the further expansion of the hole. However, since the forest is privately owned by the company that sacrifices it for the hole, activists were forced out of the forest with the help of police power – before occupying it again.
Growing up close to the Hambach forest, that received international attention in the environmental and climate movement, I’ve been concerned about one question for a very long time: How can we replace an ancient forest that is destroyed for mining purposes?
“If we are moving several villages, people, and a motorway for the open-cast coal mining, why don’t we also move the forest?” That is how people in my region would have addressed this question in the past. Believe me or not, that’s exactly what has been done. At one end of the gigantic hole, the largest artifical hill worldwide was created and recultivated with trees. It serves the region now as a recreation area, comprising an about 70km network of hiking trails. “Forest is forest. There is no difference”, people say in my region. So why be concerned?
But is it really that easy? Are humans really able to shape a new forest within a few years as a replacement for a destroyed ancient forest, that has the same value for biodiversity and people? And will the planted trees provide an appropriate habitat for all mammals, birds, insects, spiders, herbs, lichens and other important life forms that used to inhabit the lost forest?
In many countries around the world, there are nowadays regulations regarding compensation and restoration measures that mining and other companies have to fulfil when their activities destroy land. However, in reality, is it always possible to restore an ecosystem that has undergone complete degradation from a natural forest to a mining site, back to its original state and biodiversity value? Otherwise, it is possible to shape a new ecosystem with the same values at another site – like it was aimed with the planted artifical hill as a compensation for the destruction of the Hambach forest? Fortunately, there are ecologists who have learned the answers to these questions. Closely monitoring the process of ecosystem restoration they can tell how successful undertaken restoration efforts are for biodiversity.
So, now that we’ve already practiced thinking in great dimensions, let’s undertake a great jump to another mined forest – we’re jumping off Germany, over Italy and the Mediterranean Sea, crossing the Arabian Peninsula and the Indian Ocean, passing Australia and are finally landing in… Auckland! Well done! We’re standing here at the Hunua Quarry site, near Papakura in South Auckland. It is part of the Hunua ranges that consist of over 20 000 ha of native forest, comprising tawa, podocarp, kauri–hard beech, and taraire forest as main vegetation types.
The Hunua Quarry is managed by Winston Aggregates, New Zealand’s largest aggregates provider. As a restoration measure, in six years over 140 000 plants have been planted in this highly modified habitat after quarrying. The aim is to provide a new forest as a replacement of the forest area destroyed. Next to the restoration area, you can still recognize unrestored areas of exotic grassland that have established after quarrying, as well as undisturbed mature native forest.
Researchers from Lincoln University (Mike Bowie and colleagues) studied the invertebrate communities at Hunua Quarry, including wetas, beetles, cockroaches, crickets, spiders, centipedes, earthworms, ants, flies, mites, moths, slugs and snails, amongst many others. Although rather small animals, invertebrates are essential for the functioning and health of ecosystems, thereby making an important contribution to biodiversity. The objective of their study was to develop a better technique for the assessment of restoration success after mining, using invertebrates as bioindicators.Bioindicators are species that react sensitively to changes in their environment so that they can be used to assess the quality of an ecosystem.
The researchers collected invertebrates in the undisturbed mature forest, in restored areas, as well as in the unrestored exotic grassland. They compared how many and which invertebrates were living in the respective areas. Interestingly, the undisturbed mature forest, the restored areas, and the unrestored exotic grassland were characterized by very different invertebrate communities. The invertebrates found in the six-year-old restored areas were mostly still very unlike those found in the undisturbed mature forest. For instance, the researchers were able to collect eight times more cave weta in their pitfall traps in the undisturbed mature forest than in the restored areas. In addition to cave wetas, the mature forest also harboured many spiders and beetles. Hence, if the forest restoration process is successful, it is expected that more cave weta, spiders and beetles typical for mature forest will inhabit the restored sites in the next years. At the same time, fewer exotic snails, slugs and earthworms that were found to be characteristic for the unrestored exotic grasslands are expected.
All in all, the study showed that invertebrates might tell us more about the quality of a forest than you would easily see yourself. Hence, studying invertebrates as bioindicators has great potential for making better decisions in ecosystem management and for restoration projects. I hope that research about restoration will also raise public awareness for the complexity of biodiversity and the needs for appropriate habitats. Perhaps, I will hear many people around the Hambach forest region in Germany say: “Forest is not like forest. We need to consider old natural forests as valuable habitats and save them from vanishing, not only for the sake of spiders and beetles.”
“Captain, we’re losing ground! The phosphate is encroaching.”
“Retreat to higher ground! It’s safer up there.”
“Send in the spiders and beetles! Earthworms, you stay here.”
“Defend the Buffer!!!” [insert battle cry]
If the plants and insects at Bankside Scientific Reserve could talk, they would probably sound something like that. While this 2.6 ha protected area is home to important communities of native species, it is under threat of phosphate intrusion and the breaking-up of the local habitat. Humans have greatly altered the lowland Canterbury Plains of Aotearoa/New Zealand. With the recent switch to irrigated dairy farming, very few patches of undisturbed native dryland vegetation are left in the region. This change in land-use has led to a higher reliance on fertilizers as well as water for irrigation, which has come with its own set of challenges.
Aggressive introduced weeds, pasture grasses and forbs, have also begun to dramatically alter the functioning of native plant communities. Remnant areas are both vulnerable and essential to maintaining native ecosystems (hence the need to defend the buffer). Mike Bowie and his team investigated one of these remnant areas, looking at soil chemistry, plant distribution, and soil invertebrates along transects at the Bankside Scientific Reserve. Their study identified the current conservation value of the reserve, assessed how persistence of native biodiversity changed along the pasture-reserve gradient, and evaluated the effects of the likely infringement of irrigation water and nutrients from adjacent farmland.
The vegetation of Bankside Scientific Reserve had been studied previously by Malloy (1970), who provided a detailed catalogue of the flora, listing 66 native vascular plant species. Jenson & Shanks (2005 – unpublished DOC Report) also completed a one-day reassessment of the site, but recorded only 14 native species. Today, the vegetation at the reserve can be described as a patchwork of native woody shrubs, made up mainly of makahikatoa, matagouri, and dry grassland. As Mike and his team point out, the modified soil conditions seem to have made the reserve not as well suited for native species, and better for the invasion by exotic plants. Compared with detailed surveys prior to the dairy conversion, only 31% of the original 65 native vascular plant species were found in the current study, and 27 new exotic species had arrived since the original survey.
As for the underground conditions, soil nutrient concentrations and pH were lower in the reserve than in the surrounding farmland, with peaks of nitrate and ammonium being recorded at the boundary. Meanwhile, soil phosphate was higher in lower-lying areas within the reserve. Four species of endemic (Megasolecidae) earthworms were found in the reserve, but not in the neighbouring pasture.
Other cool finds included ground wētā (Hemiandrus sp.) and trap door spider (Cantuaria dendyi). A 2011 survey by Emberson et al. (2011) also found the large rare rove beetle, Hadrotes wakefieldi, and several species of long-horn beetles. As opposed to the earthworms, the diversity and abundance of beetles and spiders in the reserve was similar to that recorded at least 10 m into surrounding farmland.
Another interesting take-away from this research, is the importance of areas of higher elevation. Although elevational differences between highest and lowest contours were <5 m in the study, the higher areas were very important in avoiding environmental change from agricultural drainage and effluents. They helped to maintain environmental conditions that were closest to the original habitat, providing the best-suited habitat for native plants and animals.
Image created by Catherine Priemer
The work of Mike Bowie and his team, along with previous studies, points out the significance of small remnant reserves for the conservation of indigenous invertebrates found in these rare dryland ecosystems. Their findings also suggest that lime and phosphate fertilisers may represent the main threats to dryland nature reserves in irrigated dairy landscapes. Above all, their research underlines the importance of the soil environment in sustaining the variety of plant, animal, and insect life in this unique environment.
Taking the team’s findings into consideration, the maintenance of a buffer zone – a protected zone established around sensitive or critical areas – could be beneficial in lessening the impacts of human activity and land disturbance around remnants, such as Bankside Scientific Reserve. To do this, native species can be planted between agricultural and conservation areas, to help protect sensitive habitat. The key take-away: Defend the Buffer!
Although I was vaguely aware of dung beetles and their role in the ecosystem, I finally became interested in them while participating in giraffe research in South Africa. I’ll never forget the time when I was finishing up my giraffe work for the day and I stopped to watch a couple of dung beetles who were squabbling over a single ball of dung (poop). What I had perceived to be a relatively gentle disagreement escalated quickly when I watched one demolish the other with a long-time favourite move from the World Wrestling Foundation, the Brainbuster. You know the one.
Dung beetles play an essential role in the environment. However, they fly a bit under the radar, which is why they are often called nature’s “unsung heroes.” There are over 100 species of dung beetle, each choosing one of three strategies: rolling, tunneling, or dwelling in dung. Not only do they eat and live in animal dung, but they increase the freak by reproducing in it and burying it. This ensures their offspring have plenty of food for when they hatch.
As gross as it is, this burying behavior strongly limits the growth of vertebrate parasites, which is tremendously helpful to the rest of the ecosystem. They help remove animal dung from the surface environment with incredible efficiency and speed. In some places, the beetles can eliminate a pile of dung in less than 10 minutes, where the ground would otherwise be carpeted with it.
Dung beetles are very widespread, found in many different habitats across all continents except Antarctica. Like many species, dung beetles appear to be harmed by the break-up of natural environments. This fragmentation reduces the size of undisturbed, or core, habitat in the centre and creates isolated habitat patches. The environment along the edge of a habitat is usually quite different from the core. In forests, for example, it’s typically windier and sunnier at the edge of the forest than in the centre.
Edges are not only susceptible to environmental challenges, but also to human impacts. They are more vulnerable to fire, as well as illegal harvesting or collecting of plants or animals by humans, simply because they are more easily accessible. Some of these impacts along the edges don’t stay localized, but can radiate into the core habitat as well.
Edges are in fact an important habitat, because they support species that like transitions between different habitats. However, as humans continue to break up large habitats, with roads or communities for example, the amount of edge habitat increases, while core habitat shrinks. This challenges the animals that rely on core habitat. Additionally, the edges of habitats typically support fewer species than the core. We don’t want to consistently change habitats around the world to ones that support similar and fewer species.
Buffer zones are areas around a sensitive, often legally protected, environment that are typically managed to reduce edge impacts on the borders of a sensitive area. Sometimes buffer zones have methods to exclude humans or livestock, such as fences. Sometimes they are simply designated areas without active protection measures. Relatively little is understood about how effective buffer zones actually are for some species.
Back to dung beetles, we typically see fewer individuals and a less diverse group of dung beetles along habitat edges than in the core, because they are a group that tends to be quite affected by human activities. For example, because they are in constant contact with dung, they are exposed to pesticides that livestock ingest, which has been causing population declines. But how do buffer zones impact dung beetle diversity and density along the edge of protected habitats?
Andrew Barnes and his colleagues, including the late Rowan Emberson from Lincoln University, decided to find out. The montane rainforests in Sub-Saharan Africa are shrinking rapidly, largely due to deforestation for agriculture and grazing. There is also nearby habitat decline that often comes with agriculture. The Ngel Nyaki forest reserve in Nigeria is a heavily fragmented area. To test how dung beetles would respond to increasing edge effects, the researchers applied experimental habitat restoration treatments to certain areas along the edges. For the restoration, researchers excluded livestock with fencing, created and maintained firebreaks to help block fire, and allowed passive natural regrowth of the floral community. This combined restoration occurred in 200 metre buffer zones over the course of three years.
The impact of these buffer zones was remarkable. In the forest next to the restoration area, the dung beetle population size increased by over 50% compared to the unrestored areas. Perhaps more important was the difference between dung beetle populations in the edge and habitats. Before the restoration, there were many more species of dung beetles in the habitat core and relatively few in the edge. After the restoration, that difference disappeared, meaning that the buffer zones successfully mitigated the challenges that are typical of edges for dung beetles. The restoration also led to the return of certain species that had previously locally disappeared in the degraded habitat.
These changes are incredibly pronounced and occurred after only three years and with small levels of restoration. While firebreaks do require active maintenance, it is encouraging that even relatively minor land-use changes around protected areas can make a world of difference for many species. Relatively few studies have been completed about the effectiveness of buffer zones, so this is a single, but vital, drop in a much larger pot of conservation decisions.
After all, we want all dung beetle species to survive, no matter how gross or freaky, to tidy up after vertebrates and perhaps to get more inspiration for wrestling moves.
One of the many great fascinations of New Zealand is the absurd number of bugs found here that are found no where else on Earth. What’s a bug, you might ask? They’re the six-legged creepy crawlies you find everywhere. They are a part of your life, from the obnoxious house fly in your room to the big, bold beetle in the garden! Well, technically, I mislead you with the name bug. Bugs are a single group of piercing-sucking insects; the correct term to describe errant creepy crawlies is insects.
Aside from being a nuisance in the home, what do New Zealand’s insects do? They provide excellent services to our ecosystem, whether churning up dirt, pollinating flowers, or controlling noxious weeds. They also serve as an essential part of the food web and are a key to the survival of many birds and lizards.
A friendly, Robust grasshopper says hello! This photo I took in the Mackenzie district shows one of our largest grasshoppers. They’re excellent grazers of lichens and mosses. Historically they provided great nutrition for many birds and lizards.
Despite their abundance, insects are massively understudied both globally and in New Zealand. We must understand how our insects contribute to our ecosystems and what might happen when new insect species arrive in our country. Species not previously found in New Zealand (nonindigenous creatures) have been a massive threat to New Zealand’s native biodiversity over the past 200 years.
Of the non-indigenous species in New Zealand, much of the focus has been on mammals, like stoats, and plants, like wilding pines. This work is essential because these sorts of species have huge impacts on our environment and our economy. But what effects do the over 2000 introduced insect species have on New Zealand? A study by Brockerhoff (in 2009) featuring Lincoln University’s Dr Cor Vink, attempts to determine the threat of new insects to New Zealand’s ecosystems.
The threat of introduced insects was recognised soon after European arrival. From what we know few of these species are capable of affecting native ecosystems aside from the well-studied Vespula wasp.
The currently accepted view is that new insects do not generally hurt our ecosystems. However, as New Zealand’s ecosystems are often so understudied there is little way for us to measure the effects of new insects on the environment. Across most of the world, the arrival of new insects can be a catastrophe with substantial environmental and economic impacts.
A photo by Will Frost of a typical Mackenzie Basin floodplain grassland. A habitat type threatened by new species of weevils and the expansion of dairy farming.
So far New Zealand has avoided such a catastrophic invasion. Brockerhoff (2009) suggests that perhaps our intact native ecosystems repel insect invasions well compared to other parts of the world. While our forests have repelled invaders so far, the threat of climate change may alter the balance in the war of plants and insects.
Brockerhoff (2009) aimed to investigate the effects of insect invaders across a range of New Zealand’s habitats. It was found that over 200 insects capable of damaging forests have been found in New Zealand but have had minimal impact on our native ecosystems. Several generalist moth species and a passion vine hopper have had minor effects without significant damage. In grasslands, several weevil species have been found all over New Zealand, even as high as 2800 metres, but their impact on the surrounding environment so far seems to be minor. These results suggest that all is well for New Zealand’s ecosystems. However, with rising temperatures creating more optimal conditions for invaders there could be an increase in foreign insect invaders.
When species reach more significant numbers, their effects can start to worsen. Vespula wasps are well documented for their disruptive effects in beech forests. They feed on honey sap and compete with native birds for this resource. Worse still, these wasps predate on many native insects, some requiring a 90% reduction in Vespula wasps to survive.
The Argentine ant spreading through New Zealand and is also of grave concern. In large numbers this ant has the ability to displace native ants and often eradicate many other native insects in the soil ecosystem.
A photo by Will Frost showing a honey-dew beech forest from Craigieburn Forest Park which is threatened by Vespula wasps.
So far many of the more harmful insect species are isolated to human-altered habitats. And insects which make it to intact ecosystems fail to make an impact. As these insect’s populations build over time and more begin to enter the country as temperatures warm the threat of invasion into native forests may increase.
Many insects are selective of the plants they consume due to plant defences and palatability. This is true even for generalist insects that specialise on many plants. This likely explains why so far our plants have provided protection from so many would-be insect invaders.
Honey dew being produced by scale insects. A rich food source for wasps. Photo from Adrian Paterson
Brockerhoff (2009) suggests that for these reasons the greatest risks to our ecosystems now are from generalist insects, especially those which don’t rely upon plants. Generalist predators, like Vespula wasps, threaten the whole ecosystem’s natural processes. Due to their ability to consume the sugar produced by scale insects. These wasps prey on the majority of native fauna in beech forests to provide food for their young. When in huge abundances the composition of insects in the forest and availability of sugar sap is hugely reduced. If more generalist insect species with no natural predators were to arrive within New Zealand the impacts would be even greater.
To reduce the threats to our ecosystems in future, introduction of more insects for biocontrol should not be taken lightly. We are fortunate that few exotic insects have been established in New Zealand’s native habitats. However, many of the subtle effects caused by invasive insects are not yet known, more study is needed to grasp how these effects are impacting the ecosystem.
In the future, climate change and habitat disturbance could allow new insects to arrive and threaten our native ecosystems. We know enough now to say our environment is safe from hugely adverse effects; however, the future is uncertain. Developing a greater understanding of how these creepy crawlies subtly affect our ecosystems is paramount.
This article was prepared by Master of Science postgraduate student Will Frost as part of the ECOL608 Research Methods in Ecology course.
Brockerhoff, E. G., Barratt, B. I. P., Beggs, J. R., Fagan, L. L., (Nod) Kay, M.,K., Phillips, C. B., & Vink, C. J. (2010). Impacts of exotic invertebrates on new zealand’s indigenous species and ecosystems. New Zealand Journal of Ecology, Suppl.Special Issue: Feathers to Fur, 34(1), 158-174. https://newzealandecology.org/nzje/2916
This past year I have been reading a lot of papers about mantids because I will be doing my Masters thesis on the New Zealand mantis. They are very interesting animals that fill the niche of a top predator in many habitats.
New Zealand only has one native species of mantid which is called te whē/rō in te reo Māori. Te whē/rō is a name shared with the stick insect. This relates to a tradition that Māori have where, depending on which of these insect species lands on you, this will indicate which gender your child will be. Maybe New Zealanders could bring it back for some niche (and traditional) gender reveals?
Image from Ken Vernon
The New Zealand mantis isn’t the only mantid species in New Zealand though. Since the 1970s we have had a second species in our country. Spreading from Auckland and across the North Island, the South African mantis quickly established itself in New Zealand. This South African invader is also well established in Nelson on the South Island.
These invasive mantids have caused the decline of our native mantis on the North Island. This impact is likely driven by the female South African mantis that eat our native mantis males. These males follow their noses to the exotic female only to find out that it is a dinner date, and they are on the menu.
NZ ootheca (Jon Sullivan)
The native mantis is more of a gentle species, where the females are unlikely to try and eat their mate. They don’t live for very long, perhaps six months in the wild. Mantids need a way to survive the winter and ootheca (little mantid egg cartons) protect their eggs while they develop. Both mantid species in NZ have ootheca, though they can easily be told apart. The South African mantis has a puffy white ootheca, which looks like a small meringue, while the New Zealand mantis has a brown ootheca that is smaller and more geometric.
The Bowies found that the New Zealand mantis preferred kowhai, native broom, lancewood, and cabbage tree, which together had 78% of the oothecae. Over half of the ootheca were found on smaller branches, predominantly non-shaded. They found that these spots were warmer and brighter than other parts of the trees and this would help with development.
Oothecae were also centred on true north, which works with most New Zealand houses and fences since most properties are also facing true north. Ootheca are attached to houses and fences that face north, maximising their sunlight. This allows developing mantids to grow quickly.
The Bowies also found that there was a size difference between ootheca in Lincoln compared to those in Palmerston North. The Lincoln oothecae were significantly larger than the egg cases up north. There could be a few reasons for this and one of them is that a larger size helps them handle the colder temperatures down here. This size difference also allowed the southern population to fit a few more eggs in their ootheca giving them a bit of an advantage.
South African ootheca (Jon Sullivan).
The study shows that our mantis has various adaptions that allow them to survive the New Zealand winters, especially by using the modified habitat we have created in New Zealand. Despite this, the New Zealand mantis is in decline. The South African mantis lay their ootheca in more sheltered spaces and produce oothecae that are larger than the locals, giving them advantages. They can even lay an ootheca without mating and it will hatch successfully.
Just like those male mantids, we’ll be praying for a happy ending!
This article was prepared by Master of Science postgraduate student George Gibbs as part of the ECOL608 Research Methods in Ecology course.
Bowie, M. K.; Bowie, Michael H. 2003. Where does the New Zealand praying mantis, Orthodera novaezealandiae (Colenso) (Mantodea: Mantidae), deposit its oothecae? New Zealand Entomologist 26(1): 3–5. (https://doi.org/10.1080/00779962.2003.9722103)
