There are two families of wētā in New Zealand. The Anostostomatidae are wētā we often associate with heavy bodies, spiky legs and curved tusks – the giant, tusked, tree and ground wētā species. The Rhaphidophoridae – cave wētā – are the athletes that can jump up to 3 metres in a single leap!
There are over 50 species of cave wētā in New Zealand. Like all of our wētā species, cave wētā are endemic. However, similar creatures live in many other parts of the world. In Australia, they are called camel crickets. In other places (the Americas, Europe, Asia and South Africa), they are called long-legged cave crickets. Scientists believe the wide distribution of wētā-like creatures is due to their ancient existence on Gondwana.
Nature of science
Cave wētā are part of a very ancient group of insects. They have not changed much over the centuries, according to their long fossil history. Scientists use fossil history as evidence to back up these claims.
Cave wētā have many defining characteristics. They have distinctive humped backs, and their antennae meet quite close to the centre of their heads. Unlike other wētā, they do not have ears or gripping pads on their feet. Cave wētā are not aggressive. They do not kick, bite, hiss or scratch. When threatened, cave wētā quickly leap away.
Cave wētā vary in size, depending on the species. Bush-dwelling cave wētā are just a few centimetres in length and have short legs. The largest species have bodies that span 40 centimetres from antennae tips to hind legs! In general, cave wētā bodies tend to be small in comparison to their long antennae and long, slender legs.
When you are covered in a suit of armour that even extends inside your mouth, you lose touch with the outside world. To restore the sensations of taste, smell and hearing, wētā are covered with special hairs. They have special functions and are concentrated on the antennae. At night, the antennae sweep through the air to pick up the smells of the forest and the presence of friends or enemies. They keep the wētā informed about its environment when it is dark.Entomologist George Gibbs
Habitat and diet
While cave wētā are abundant in caves, they also live under rocks, loose bark and in dark damp places in the forest and open country.
Cave wētā are nocturnal scavengers. They feed on fungi, tree foliage, other invertebrates and animal remains. Wētā living near cave entrances or in smaller caves leave the caves at night to rummage in the bush for food.
It is common to see cave wētā clustered in groups near cave entrances. If space permits it, the numbers can be quite large. The groups consist of males, females, juveniles and elders. Cave wētā are not aggressive towards each other and do tend to be solitary. This differs to tree wētā, who live in social groups but only have one male per group.
Under threat from predators and habitat loss
Cave wētā – like many species of wētā in New Zealand – are threatened or endangered. This is primarily due to the introduction of numerous predator species – cats, rats, hedgehogs, possums and other predators. Cave wētā have not evolved to be able to defend themselves against these introduced species. Destruction of habitat is also endangering wētā as humans cut down forests and modify the environment.
The Department of Conservation (DOC) has multiple translocation programmes. The aim of these programmes is to breed enough wētā to start new populations in new locations. There is further good news. As wētā are invertebrates, they do not require large areas to survive. Wētā are also very good at breeding in captivity, allowing research to take place in conditions more beneficial than in the field.
Cave wētā are also able to adapt to some modified environments. For example, when humans install lighting in cave systems, wētā eat the vegetation that grows around the lights!
This Victoria University of Wellington article discusses cave wētā in detail.
Professor Steve Trewick, Danilo Hegg and Mary Morgan-Richards of the Wildlife and Ecology Group at Massey University have described and named seven new species of South Island cave wētā. Read about their work in this Stuff article.
Isobel Pickering produced this article as part of a Queen Scout project.