Habitat use by the wolf spider Lycosa hilaris (Lycosidae, Araneae) in Canterbury farmland, New Zealand

Abstract

Knowledge of the abundance and distribution of spider populations will contribute to a better understanding of the potential use of invertebrates as biological indicators in arable agroecosystems. The investigation of arthropod populations in typical farmland will clarify and encourage the conservation value of these communities and will also contribute towards the development of more sustainable agricultural practices.

The habitat preferences of Lycosa hilaris Koch (Lycosidae) and some of the environmental factors that may influence this species have been studied. Lycosa hilaris was chosen for this study as it has been reported as having a wide distribution in many natural ecosystems in New Zealand. Pitfall trapping was carried out over a period of four months (September 1999 to December 1999) to sample L. hilaris from four different habitats on a typical sheep farm in Canterbury, New Zealand. A total of 1549 spiders were captured. Adult male spiders were the most abundant, followed by females and juveniles (78.4, 18.6, and 3 percent, respectively). The total number of spiders caught in pitfall traps was lowest in September and December. Habitat preference was studied by examining, a) temporal variables (i.e., rainfall and temperature), and b) spatial variables (i.e., percentage vegetation cover, height and dry weight, and soil pH). Habitat associations were analysed using multivariate analysis, and one-way or two-way ANOVA. The distribution of L. hilaris was found to be influenced by vegetation cover, vegetation height and temperature within each habitat. An analysis of activity patterns during spring and summer found that L. hilaris was aseasonal. The number of spiders caught was too low and the duration of the study was too short to comment further on their seasonality.

A mark-recapture trial was carried out to identify some behavioural characteristics of male L. hilaris. Of the total number of adult male wolf spiders recaptured (110 individuals, 9% of the total marked male L. hilaris population), the largest recaptures occurred in the months of November and December. The highest number of recaptured male L. hilaris occurred in the pasture paddocks, while the lowest number occurred in the shelterbelts. It was suggested that the high activity and locomotor pattern of male L. hilaris is associated with the maturity stage and season. The methods employed in this study were evaluated and their utility considered for future studies on habitat preference analysis by spider communities. The potential of lycosids as biological indicators is discussed.