Weta are incredible looking creatures. They range in size, but with their big bodies, spiny legs, and curved tusks, they are one of New Zealand's most recognisable creepy-crawlies.
Weta have become icons for invertebrate conservation in New Zealand because many species are threatened or endangered. There are more than 70 species of weta in New Zealand, 16 of which are at risk.
There are five broad groups of weta:
- Tree weta
- Ground weta
- Cave weta
- Giant weta
- Tusked weta
Diet: Weta are mainly herbivorous in the wild, but are also known to eat insects.
Habitat: They are nocturnal and live in a variety of habitats including grassland, shrub land, forests, and caves. They excavate holes under stones, rotting logs, or in trees, or occupy pre-formed burrows.
Many different species
The Giant weta / wetapunga of Little Barrier is the biggest, and the Nelson alpine weta the smallest at 7 grams.
There are tree weta, ground weta, cave weta, and three species of the spectacular looking tusked weta. These males have two tusks which they use to butt other males, or rasp together to warn off competitors.
Species of weta continue to be discovered. One of the three tusked species, the carnivorous "Jaws", was found by lizard expert Tony Whittaker on Middle Mercury Island off the Coromandel Coast 29 years ago; another of them in the Raukumara Ranges on the East Coast of the North Island as recently as 1995.
Many of the giant species now only survive on protected land and many are endangered. The Mahoenui giant weta, long considered extinct on the mainland, was rediscovered in a patch of King Country gorse in 1962. Department of Conservation staff have established a new population of these on Mahurangi Island, off the Coromandel coast. Two hundred have been transferred there and after four years they are showing signs of breeding.
The challenge of classifying weta
One feature of weta conservation is the lack of basic information on their distribution, abundance, and ecology. Furthermore, there can be a great deal of variation within individual species, despite the fact there is little genetic difference between them.
Therefore, the classification and conservation of weta is an evolving process.
A Department of Conservation Recovery Plan is currently in action. It exists as a guide that can be modified as new information and conservation priorities emerge.
Population and range
Little is known about the past distribution of weta.
Several species that were once found on mainland New Zealand are now only found on offshore islands. Very little is known about these offshore island populations.
The decline of most weta is due to three major causes:
- Predation: Weta have evolved alongside native predators such as birds, reptiles, and bats. The introduction of predators such as rats, mustelids, cats, and hedgehogs has resulted in a sharp increase in the rate of predation.
- Habitat destruction: Caused by human impacts
- Browsers: Modification of weta habitat caused by browsers.
Potential for recovery
The potential for recovery is quite high for a number of reasons:
- Invertebrates respond well to management because they have a high rate of productivity.
- Many weta adapt well to modified habitat.
- Invertebrates also require smaller areas to survive than vertebrates, and can survive in tiny fragments of original habitat.
- Weta also thrive in captive breeding programmes. This is useful, because it means that research can take place that is difficult to obtain in the field.
Past conservation efforts
Management and research to date has centred on various types of giant weta, as well as several types of tusked weta, and tree weta.
Stephens Island giant weta
DOC is currently involved in several weta translocation programmes, including one with the Mercury Island tusked weta, which is being bred by Landcare Research Ltd under contract to DOC. The idea is to produce enough individuals to start a new population on another island. Where there are already enough individuals to transfer directly, as in the case of the Mahurangi Island translocation, this is done.
In another programme to test transfer techniques, 50 common tree weta were shifted from one island to another in the Mercury group two years ago, with both the new population and the old carefully monitored to ensure the transfer caused no adverse effects. There are now plans to start a new population of the Little Barrier Island giant weta on the "open sanctuary" of Tiritiri Matangi in the Hauraki Gulf, where people could readily see them.
Recovery plan in action
The DOC threatened weta recovery plan was approved in 1998. The plan sets in place a series of steps that will promote the recovery of weta. It also outlines different management options, and a work plan.
The Long-term vision of the plan is:
Volunteer with giant weta
"To maintain all Category A, B, C species and new species which qualify as threatened, in multiple self-sustaining populations."
You can help
The Department of Conservation welcomes any comments or suggestions you may have about the conservation of weta. These can be directed to the recovery group via any DOC office, or to the Biodiversity recovery Unit.
Read the Threatened weta recovery plan (PDF, 350K)