Design and use of artificial refuges for monitoring adult tree weta, Hemideina crassidens and H. thoracica
Artificial refuges were investigated for assessing populations of tree weta (Orthoptera:Anostostomatidae) in New Zealand by testing refuge design with adult Hemideina crassidens and H. thoracica in the laboratory, in a temperature-controlled glasshouse and in the field at six forest sites covering a range of altitudes and vegetation types. In laboratory and glasshouse tests, both species preferred refuges made from aged pine (Pinus radiata) to fresh pine, and willow wood (Salix alba) to pine. Neither species of adult entered holes 10 mm in diameter, but both entered holes 16 mm or 25 mm in diameter. Adult H. crassidens preferred galleries with tapering terminations to rounded terminations, refuges without Perspex observation windows, and refuges made from willow wood over those made of concrete. Adult H. thoracica preferred refuges made from concrete to willow wood. Adult mice (Mus musculus), which are potential predators of weta, were largely excluded from galleries with entrances <= 18 mm in diameter. In the field, the number of tree weta found in artificial refuges varied amongst the six sites. Weta first appeared 1.9 months after refuges were set, and reached maximum numbers after 2.14 months. Both species usually occurred singly in galleries and most frequently in long, upturned galleries. The number of weta in refuges varied little with height above ground, but there is evidence that this was positively correlated with the number of weta in natural cavities and was higher where rodents were controlled. There was no difference between the number of weta found in refuges in the interior of a forest and near the forest edge
Print Book, English, ©2006
Science & Technical Pub., Dept. of Conservation, Wellington, N.Z., ©2006