• The Listener
  • North & South
  • Noted
  • RNZ

How a remarkable native insect is being saved

Brachaspis robustus, the robust grasshopper, has only ever been seen in the Tekapo, Pūkākī and Ōhau river catchments in the Mackenzie Basin. Photo/Tara Murray.

Principles of bird conservation are helping to save another remarkable native you’ve never heard of.

“The truth is that we need invertebrates but they don’t need us. If human beings were to disappear tomorrow, the world would go on with little change. But if invertebrates were to disappear, I doubt that the human species could live more than a few months.”

– Biologist E. O. Wilson

We live in a world teeming with invertebrates: animals with no skeleton, bones or backbone. Many of them are insects, darting, scuttling, hopping and creeping, overhead, underfoot and out of sight.

Hold the fly spray! These are the unseen cogs of the natural world. They pollinate plants, feed animals and dispose of the dead, fertilising soil in the process. Without them, our dirt would die and be covered with animal shit – and our birds would starve. So would we.

Although it has been estimated that there are some 200 million insects for every human alive today, many species are in a spot of bother. Insects are hard to catch and count, so the truth is, hard data is often missing or imperfect. Recent claims of an “insectageddon” within the year are hyperbole. Yet many insect populations appear to be crashing – just like those of countless larger animals that are easier to study.

You have permission to worry.

In New Zealand, 12 species of invertebrate (that we know of) have followed nine species of moa, the world’s largest eagle, the world’s largest gecko, and others into oblivion.

The most recent extinction is probably that of the Eyrewell ground beetle, a shiny, black, flightless creature last seen in 2005. Despite eight years of pleading by the Department of Conservation, Ngāi Tahu Farming converted the beetle’s one known habitat – a single pine plantation called Eyrewell Forest – to dairy pasture. The last gleaming Holcaspis brevicula likely met its end in a wood shredder.

“People just don’t seem to get that insects are important,” says entomologist and conservationist Tara Murray, a senior lecturer at the University of Canterbury. “They have so many functional roles, not the least of which is being food for all those cute birds.”

The endangered Canterbury grasshopper Sigaus minutus may be among the first to benefit from strategies learned in the conservation of the robust grasshopper. Photo/Tara Murray

Murray is interested in looking after our most-threatened insects, those clinging onto life with a micropterous  (undersized) wing and a prayer. “These species may have lost their individual role as ecological service providers, but are incredibly important as they represent the tip of the mass extinction iceberg,” she says.

To battle further extinctions, Murray exploits the principles of bird conservation she learned at an early age. Her father was a ranger for the old Wildlife Service, and the family lived on the West Coast before moving to Twizel. As a child, Murray was a keen volunteer at the kakī (black stilt) captive breeding facility near Twizel.

“Most of the threats to insects are the same as those to other species – habitat fragmentation, introduced predators and weeds. Insects benefit when we remove these threats for the protection of other species, but we rarely initiate them specifically to protect insects.”

Murray didn’t have to look far for a suitable insect candidate. Close to the kakī’s Mackenzie Basin braided-river wading pools lives one of New Zealand’s most stunning insects: the robust grasshopper. Small populations, close to extinction, live in the Tekapo, Pūkākī and Ōhau river catchments. And nowhere else in the world.

“When you look at them up close, they are really quite amazing,” says Murray.  “They are like little grey tanks, all short and squat with beautiful grey or rusty red ridges.”

PHD student Jennifer Schori searching for robust grasshoppers at the Tekapo Triangle in 2015.  Photo/Courtney Hamblin.

If Game of Thrones ever needs to cast a grasshopper in fantasy armour (available in either riverstone grey, black or orange), Brachaspis robustus is a shoo-in. Murray now breeds these grasshoppers, aiming, one day, to release enough to ensure the species’ survival – the same principle that has saved the tīeke, the kakī and many other New Zealand birds.

The action takes place in Murray’s lab, – and also behind a 500m hedgehog- and stoat-proof fence within the “Tekapo Triangle”, an area of Crown land transferred to DoC last year.

Captive rearing requires a close understanding of the grasshopper’s life cycle, from sexual habits to egg laying and food preferences. B. robustus eggs, for instance, need low temperatures as a signal to hatch – a requirement, by the way, that makes them critically sensitive to a warming world. However Murray and her team have already learned enough to raise a generation of young “hoppers” to adulthood outside the lab. Although the fence cost funders Te Manahuna Aoraki (a large-scale conservation project launched last November with several sponsors) about $130,000, the insect’s size makes them relatively cheap to conserve.

The 500m hedgehog- and stoat-proof fence. Photo/Tara Murray.

Grasshopper feed doesn’t exactly break the bank. An adult female robust grasshopper – which at 38-42mm is almost twice the size of a male – gets through only a couple of leaves a day. “But if you give them a dandelion, they eat it in minutes.”

Many of the grasshoppers have been captured by Murray’s PhD students, including 26-year-old North Cantabrian Jennifer Schori. Her methods include the “grasshopper walk”: a bizarre technique requiring knee pads and a sharp eye.

“The most difficult part is spotting them, because they blend in with their surroundings so well,” she says. “We walk slowly, waving a foot low to the ground over the rocks in front before taking a step. When the foot throws a shadow over the ground it is often enough to disturb the grasshopper and make it hop. Usually you have to kneel as close as you can to the grasshopper without disturbing it – hence the knee pads – and then quickly cover it with a cupped hand.”

Newspaper reports that the robust grasshopper is a useless hopper are unfounded, says Murray. “They can actually jump, they just don’t land very well. On a hot day, an adult male can jump up to 1.5m, multiple times. Females are bulkier, so they don’t jump as far. These grasshoppers freeze as a first defence. If they do jump, it often ends as a back flop, belly flop or general ‘thock’ on the ground.”

Let’s hope Murray’s “team grasshopper” allows our handsome, dandelion-chomping belly-flopper to become a common sight on South Island river banks.

As a Canadian entomologist once said: “The world is rich in small wonders – but so poor in eyes that see them.”

PHD student Jennifer Schori giving a robust grasshopper an ID mark using a paint pen in the lab at University of Canterbury. Photo/Stephanie Galla.

Insectoids

  1. Only 1363 terrestrial insect species have been classified under the New Zealand Threat Classification System – but the total number in New Zealand is estimated to be more than 20,000, many unnamed. This means that not enough is known about 90-95% of our insect species to even assess how endangered they are.
  2. The robust grasshopper is one of 764 insects known to be threatened or at risk.
  3. DoC has only three insect specialists.
  4. All grasshoppers in New Zealand are endemic (meaning native and restricted to our shores) except the migratory locust, which is the only grasshopper in New Zealand to have wings capable of flight.
  5. Seventeen native grasshoppers have been named, seven others recognised, but many more species are likely to exist.
  6. Wētā are not grasshoppers, despite their genus name Deinacrida, literally “demon grasshopper”.
  7. Nearly all native New Zealand grasshoppers live in the South Island, are flightless – although they can hop – and silent. Many live in alpine regions.

SOURCE: University of Canterbury entomologist Tara Murray.

The hedgehog can decimate insect populations with a limited range.

The killer

The hedgehog is one of the most underrated killers of endangered native insects. “People just don’t realise how many there are out there and how many insects they hoover up,” says conservationist Tara Murray. “Our grasshoppers don’t sing like most of their international cousins. They smell. And robust grasshoppers are the insect equivalent of the kākāpō – they freeze.” The robust grasshopper has evolved superb camouflage to evade native birds swooping overhead. Unfortunately, their smell is a megaphone to introduced mammal pests such as hedgehogs. Unlike cats, hedgehogs will sweep a food patch, meaning that if they find a good resource, they will keep feeding there. This can decimate insect populations with a limited range.

This article was first published in the May 2019 issue of North & South.

Follow North & South on Twitter, Facebook, Instagram and sign up to the fortnightly email.