Predictors of relative abundance of tree weta (Hemideina thoracica) in an urban forest remnant

Restoration of urban forest remnants is an increasing activity worldwide, but the effects of restoration efforts on local wildlife in urban remnants remain poorly understood. Understanding the benefits of restoration can also be confounded because of difficulties in monitoring the abundance of representative species, or understanding their ecological requirements. We studied tree weta (Hemideina thoracica) in an urban kahikatea (Dacrycarpus dacrydioides) forest remnant in Hamilton City: we estimated relative abundance of tree weta, and examined the relationship of weta occupancy of artificial refuges to tree size, bark depth, distance from a centrally lit path, and distance from the edge of the remnant. Estimates of tree weta abundance were comparable with those at other mainland sites. A range of tree species supported tree weta activity, but more weta were encountered on large trees, and fewer on kahikatea relative to other tree species. Occupancy records from 40 artificial refuges on kahikatea trees over 28 consecutive days revealed that tree stem diameter and proximity to the central path predicted occupancy on the dominant kahikatea trees. The data indicate constructed features of urban remnants, such as paths, can negatively affect habitat quality in urban forest remnants. Maintaining large trees in urban parks can provide critical habitat through the provision of natural cavities for weta. Erecting artificial cavities on these trees to gain estimates of tree weta density can also provide indications of ecosystem recovery, for example, after pest removal.