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NZ Biology: The Big Friendly Giants - The Giant Weta

Big Friendly Giants - The Giant Weta!

This mini unit looks at the giant weta and makes use of Mahoenui Giant Weta an episode on your Meet the Locals DVD.  Students will find out how the weta evolved, why it's threatened and how we are protecting this ancient insect.

You'll find links to websites and learning tools which provide practical activities to develop your students' knowledge and skills. Background information is also provided within the learning activities.

Years: 7, 8 and 9
Levels: 3 and 4

Achievement objectives
Living world

Students will:
Explain how living things are suited to their particular habitat and how they respond to environmental changes both natural and human induced.

Appreciate that some living things in New Zealand are quite different from living things in other areas of the world.

Duration: About a week.

Learning outcomes
1. Sort factors on a T chart that show why weta have survived for so long and factors which are leading to their demise.
2. Research and publish concise information in a bio-box that shows why the giant weta is so unique.
3. Discuss and consider alternatives for successful recovery plans.
4. Devise and publish a recovery plan for the giant weta that has good chance of success.

Teaching and Learning Activities

1  What's an insect?
Here's a quick activity to check your students' prior knowledge about insects.

2 In days gone by
Students consider why New Zealand has creatures living here that are different to anywhere else in the world. They look at factors that helped the giant weta survive and factors that are now leading to its demise.

In days gone by uses the information below and can be done in pairs or groups.

Giant weta are one of our most ancient types of land animals.

Their design is virtually the same as fossil weta found in Queensland and they date back 190 million years - long before Australia and New Zealand parted company during the split - up of Gondwana.

Weta have flourished and diversified during New Zealand's last 80 million years of isolation and more than 70 endemic species have evolved.

Some reached a gigantic size and without mammals the giants came to occupy the same sort of night-living niche that rodents occupied in other countries.

When rats and mice started living here most giant weta species couldn't compete. Their food was eaten and they became food for rodents. Numbers plummeted.

Weta grow and breed slowly. Wetapunga, the biggest of the giant weta, take around 18 months to reach maturity and they only breed towards the end of their two years of life.

3 Life's essentials
Bio boxes can quickly profile almost any person, place or animal. They're tightly written giving background information at a glance. They answer essential questions like:

  • Weight?
  • Length?
  • Food?
  • Habitat?
  • Threats

A picture adds value.

Get your students to design a bio box for the giant weta and find out a few essential facts at the same time.

Useful link is:
NZ Ecology Gigantism in Insects  

Useful life cycle information for the bio box is:

  • The eggs are oval-shaped and 7 mm long and 2.5 mm wide. They're laid 50 mm deep in the soil.
  • The nymphs start off as mini - weta about 5 mm long.
  • They moult (grow out of their skin) ten times before beginning adult life.
  • Adults are about 70-80 mm long but females grow bigger than males.

4 Good place for a giant
Hardly any giant weta remain on the mainland because they've fallen prey to cats, rats, stoats, ferrets and weasels. They only survive in places where they can be protected from these predators.

Protection and recovery programmes can prove tricky too. Share this story with your students and discuss in class whether they would have approached the problem in a different way.

The wetapunga, the biggest of the giant weta has to share Little Barrier Island with the kiore, the Polynesian rat. In the past it was thought that kiore were reluctant to climb the trees that wetapunga lived in so they didn't have huge impact this giant weta's population.

DOC rangers eliminated the feral cat population on the island which was great for the birds and lizards, but surprisingly, not so good for wetapunga.

Kiore were the cats' main prey and now the rat population has grown! That's bad news for wetapunga. Its numbers are dwindling.

Watch the video, Mahoenui weta It's an episode on your DVD. Get the class to focus on looking for these things and discuss them after viewing:

  • What saves these giant weta from predators?
  • What's the biggest danger for these weta?
  • Have these weta evolved any defence systems against rats that really work?
  • What feature does the female have that helps the female lay her eggs at a safe depth?
  • What else is being done to protect these giants of the insect world?

5 Saving a species
By studying endangered species of weta and gathering information on their ways of life, we can establish new populations of giant weta in safe places.

The Mahoenui giant weta, is one of Landcare Research's Conservation Flagships. It's an iconic New Zealand species so the recovery programme wants to significantly improve their management and recovery.

Scientists work out why weta populations are declining, they establish original habitat characteristics and improve the effectiveness of reintroduction and restoration techniques.

In this activity the students devise a recovery plan of their own for the protection of weta on a mainland site. This recovery guide will help them formulate a plan and gives them handy hints that may see them think of ideas like the examples below.

  • Scientists are using miniature tracking equipment, such as tags, tiny transmitters, and lights fastened to the insects' thorax, to help track weta in their haunts.
  • They collect eggs, hatch them, and raise young weta in captivity, preparing them for release back into the wild.

6. Active involvement - an optional extra.
Motels for weta

Tree weta like living in holes in trees but there really aren't that many holes. That's why they dig under stones or chew through rotten logs to make their homes. Weta motels help bring weta to your backyard. They're placed in trees, under trees and even on fence posts.

This 5 star motel is great but it takes a little while to make.

This three star weta motel is easier and a one star motel works well too - some pieces of bamboo hanging in a tree!

Weta prefer motels without windows but some people like to peer at them to see what they're up to.

Make your windows from perspex or plastic from a bottle. You need to be able to remove them for cleaning because they go mouldy and they need shutters.

Weta will live in motels with windows as long as their gallery is deep.

Weta adapt well to living in a modified habitat. The females lay 100 -300 eggs so if you build a home they like, then weta will live there and numbers will grow!

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