Praying for time: the rise and fall of the New Zealand mantis

While the decline of the giant panda, great apes and various cetacean species have long garnered headlines, our scale prejudice has meant invertebrates have fared rather less well. Only with the worrying spread of colony collapse disorder (CCD) in bee hives have insect-themed stories gained public attention; yet most of the millions of other small critters remain on the sidelines. I've often mentioned that overlooking these small marvels could backfire on us, considering we don't know the knock-on effect their rapid decline - and possible near-future extinction - would have on the environment we rely on.

One such example here in New Zealand is our native praying mantis Orthodera novaezealandiae, which for all we know could be a key player in the pest control of our farms and gardens. Mantid species are often near the apex of invertebrate food webs, consuming the likes of mosquitoes, moth caterpillars and cockroaches. I admit that they are not exactly discriminating and will also eat useful species such as ladybirds or decorative ones like monarch butterflies. However, they are definitely preferable to pesticides, a known cause of CCD today and an acknowledged factor of insect decline since Rachel Carson's pioneering 1962 book Silent Spring.

Of course, we shouldn't just support species due to their usefulness: giant pandas aren't being conserved for any particular practical benefit. From a moral perspective it's much easier to convince the public that we should prevent their extinction than that of the rather uncuddly mantis. We still know so little about many insect species it's difficult to work out which need to be saved in order to preserve our agribusiness (versus all the others that of course should be preserved regardless). I’m not averse to careful extermination of plagues of locusts or mosquitoes, but indiscriminate destruction due to greed or stupidity is well, stupid, really.

Down but not out: the New Zealand praying mantis Orthodera novaezealandiae

Back to O. novaezealandiae. I've only seen New Zealand's sole native mantis species three times in the 'wild': twice in my garden in the past two years and once in my local reserve before that. What is particularly interesting is that since initial descriptions in the 1870's, hypotheses regarding its origin appear to have evolved due to patriotic trends as much as to factual evidence. Late Nineteenth Century accounts of its spread suggest an accidental importation from Australia by European sailing ship, since it is a clumsy, short-range flier and seabirds are unlikely to carry the insects - and certainly not their cemented oothecae (egg sacks) - on their feet.

However, some Victorian naturalists thought the insect was incorporated into Maori tradition, implying a precolonial existence. In contrast, A.W.B.Powell's 1947 book Native Animals of New Zealand refers to the native mantis as Orthodera ministralis (which today is only used to describe the Australian green mantis) and the author states it may well be a recent arrival from across the Tasman Sea. So the native species may not be particularly native after all! I find this fascinating, insomuch as it shows how little we understand about our local, smaller scale, wildlife when compared to New Zealand's birds, bats and even reptiles.

The specimens in my garden have lived up to their reputation for being feisty: they seem to size you up before launching themselves directly towards you, only for their wings to rapidly falter and force the insect into an emergency landing. After the most recent observation, I looked around the outside of the house and found three oothecae, two of which were under a window sill built in 2016. These finds are cheering, as it means that at least in my neighbourhood they must be holding their own.

Perhaps their chief enemy these days is the invasive Miomantis caffra. This inadvertently-introduced South African mantis was first seen in 1978 and is rapidly spreading throughout New Zealand's North Island. The intruder - frequently spotted in my garden - has several advantages over O. novaezealandiae: firstly, it is able to survive through winter. Second, it produces rather more nymphs per ootheca; combined with hatching over a longer period this presumably leads to a larger numbers of survivors per year. In addition, and most unfortunately, the native male appears to find the (cannibalistic) South African female more attractive than the female of its own species, frequently resulting in its own demise during mating.

Humans too have further aided the decline of the native mantis with the accidental introduction of parasitic wasps and widespread use of pesticides. After less than a century and a half of concerted effort, European settlers have managed to convert a large proportion of the best land in this corner of the Pacific into a facsimile of the English countryside - but at what cost to the local fauna and flora?

Working to the old adage that we won't save what we don't love and cannot love what we don't know, perhaps what is really required is an education piece disguised as entertainment. Promoting mammals in anthropomorphic form has long been a near-monopoly of children's literature (think Wind in the Willows) but perhaps it is about time that invertebrates had greater public exposure too. Gerald Durrell's 1956 semi-autobiographical best-seller My Family and Other Animals includes an hilarious battle in the author's childhood bedroom between Cicely the praying mantis and the slightly smaller Geronimo the gecko, with the lizard only winning after dropping its tail and receiving other injuries. Perhaps a contemporary writer telling tales in a similar vein might inspire more love for these overlooked critters before it is too late. Any takers?

Amphibian Armageddon and killed-off kauri: the worldwide battle against fighting fungi

I recently wanted to visit the Ark in the Park, an open sanctuary in the Waitakere Ranges west of Auckland that uses constant predator control to protect native plants and animals. However, I was stopped by a sign stating that Te Kawerau a Maki, the Maori of the district, have placed a rāhiu or prohibition on entering the forest. Although not legally binding, the rāhui is intended to stop people walking through the area and spreading infection, serving in place of any notice by the New Zealand Government or Auckland City Council, since the latter two bodies have failed to take action. Perhaps this inactivity is because the infection does not directly affect humans or farming. Instead a fungus-like pathogen is killing the native kauri Agathis australis, one the largest tree species on Earth.

Known to live for over a thousand years and grow to over fifty metres tall, the largest kauri are seen by Maori as the lords of New Zealand's northern forests. Yet since 2009 the microscopic water mould Phytophthora agathidicida has been causing kauri dieback at an ever-increasing rate. Surveys in the Waitakeres show that most of the infected areas are within ten metres of walking paths and therefore the mould is being spread by visitors to the lowland forests who fail to thoroughly clean their shoes with the supplied disinfectant spray. In a truly David versus Goliath battle between the miniscule mould and giant trees, introduced species such as possums and pigs are aiding the former by accidentally spreading the minute spores.

Auckland Council reported last winter that the amount of affected kauri has reached 19 percent, meaning a doubling in scale in only five years. Since there is no cure for infected kauri, some scientists are now predicting the extinction of this magnificent tree in the near future. The combination of the pathogen's microscopic size with its rain-based activation after dormancy means there are currently no methods that can prevent the infection from spreading. In a way, the rāhui may just slow down the inevitable. Considering the immense kauri are home to a unique ecosystem of epiphytes, orchids and associated symbiotic organisms, the future flora and fauna of kauri-free forests may well be markedly different from the Waitakeres as they are today.

I've previously discussed the ubiquity of the unsung fungi and how prominent they are even within totally man-made environments. It seems surprising that New Zealand's authorities, so keen to preserve native birds and reptiles, are failing to take any action to at least buy time for the kauri; perhaps they have already deemed extinction as unavoidable and not worth spending public funds on.

The kauri are far from being the only organisms currently threatened by fungi or their kin. Over the past decade more than thirty snake species in the eastern and mid-western United States have started succumbing to what has been termed Snake Fungal Disease. The culprit is thought to be a soil-based fungus called Ophidiomyces ophiodiicola, with a similar organism now also thought to be affecting snakes in the United Kingdom and mainland Europe. Research suggests that up to ninety percent of infected snakes die from the condition, so clearly if humans and their vehicles play unwitting hosts to the microscopic fungal spores, the future for the world's snake population looks depressing. Although many people might not like snakes, ecosystems without them may see an explosion in the numbers of their prey animals, including rodents; to say the least, this would not bode well for crop farmers!

Perhaps the best-known of the global fungal-caused epidemics is the amphibian-decimating Chytridiomycosis, whose affects were initially recognised twenty years ago but may have started much earlier. As its spores can live in water, the responsible Batrachochytrium fungi are ideally situated to infect about one-third of all frog, toad, newt and salamander species. Again, it is thought that man has inadvertently caused the problem, as the African clawed frog Xenopus laevis is an immune carrier of the fungus and has been exported worldwide since the 1930's.

Another contributor may be climate change, as amphibian-rich forests experience temperature variations that are ideal for the chytrid fungi to proliferate in. As a final nail in the coffin - and as with bees and Colony Collapse Disorder - pesticides may play a key role in the epidemic. Agrochemicals are shown to lower the amphibian immune response and so increase their susceptibility to infection. However, the situation isn't completely hopeless: here in New Zealand, researchers at the University of Otago have used chloramphenicol, an antibiotic eye ointment, to cure infected Archey's frogs (Leiopelma archeyi). This species is already critically endangered even without the chytrid epidemic; hopefully, the cure will prove to be the saviour of other amphibian species too. This would be just as well, considering the dangerous side effects found in other treatments such as antifungal drugs and heat therapy (the latter involving temperature-controlled environments that are lethal to the pathogen).

During the past decade, over five million North American bats have been killed by white-nose syndrome, which is caused by the fungus Pseudogymnoascus destructans. Again, humans have inadvertently spread the pathogen, in this case from Eurasia, where the bat species are immune to it, to North America, where they are most definitely susceptible. The bats are only affected during hibernation, which makes treating them difficult, although brief exposure to ultraviolet light has been shown to kill the fungus. This may prove to be a cure to infected colonies, although how the UV could be administered without disturbing the cave-roosting populations will take some figuring out.

It appears then that a combination of manmade causes (international travel, climate change and chemical pollution) is creating a field day for various tiny fungi or fungus-like organisms, at the expense of numerous species of fauna and flora. The culprits are so small and pervasive that there is a little hope of preventing their spread. Therefore if conventional cures cannot be found, the only hope for the likes of the kauri might be the use of genetic engineering to either give the victim resistance or to kill off the pathogen. This science fiction-sounding technology wouldn't be cheap and its knock-on effects unknown – and potentially disastrous. The former technique would presumably not be any use to the existing populations, only to the germ line cells of the next generation. Whatever happens, our short-sighted approach to the environment is certainly starting to have major repercussions. A world without the magnificent kauri, not to mention many amphibian, reptile and mammal species, would be a much poorer one.