The ecology of the Tekapo ground wētā (Hemiandrus new sp., Orthoptera: Anostostomatidae) and recommendations for the conservation of a threatened close relative
Thesis DisciplineEnvironmental Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
At a few sites near Cromwell and Alexandra, Central Otago, there exist isolated populations of a threatened ground wētā (Hemiandrus sp.). Research was required to establish guidelines for a management programme to enhance the species' chances of long term survival. To avoid disturbance of the threatened species, a newly discovered, relatively widespread and abundant allopatric species (Hemiandrus new sp. from the Tekapo River area) was selected for study. A sixteen month sampling programme based on pitfall trapping was employed to characterise the species' distribution relative to habitat variables. By far the most important determinant of distribution was the local depth of substrate available for burrowing, wētā being most abundant where friable silty soil was deepest. Female wētā oviposit in their own burrows in late summer, and the eggs hatch in the following spring. Over two years, female nymphs develop through nine instars, and males ten. Males die soon after mating in their third summer, while females overwinter with their eggs, surviving until the following summer. Analysis of the crop contents of a sample of wētā revealed that the species is a primarily herbivorous omnivore. wētā caught in summer were significantly more herbivorous than those caught in the other seasons. Hemiandrus new sp. constructs its burrows in silty loam, and closes the top with a cap or plug. At the lower end of the burrow is a slightly enlarged chamber curved nearly horizontal. The most serious current predators of the Tekapo wētā , apart from native invertebrates, are hedgehogs and cats. It was considered reasonable to extrapolate conclusions about the Tekapo species regarding habitat requirements, life history and potential threats to the remaining populations, to the Cromwell species. Recommendations for the management of the Cromwell species (and other closely related threatened species) based on the conclusions of the research are presented, as well as suggestions for important further work.