Weak negative responses of spider diversity to short-term ‘kraaling’

Abstract

The influence of short-duration, concentrated kraaling (enclosure) has been documented for plants, wildlife, and macro-invertebrates. However, limited information is available on its impact on ground-dwelling spiders. The purpose of this study was to assess the effect of short-duration kraaling, time since cattle removal, and microhabitat variables on spider assemblages in Matabeleland North Province, Zimbabwe. We used a matched-pair and space for time design (inside vs outside previously kraaled inclusions) across 11 sites, using four cattle herds (H1, H6, H7 and HNguni). Spiders were sampled in the early and late rainy season with pitfall traps left open for 14-day sampling periods and emptied twice in each period. We captured 634 spiders, comprising 63 species in 44 genera and 18 families. The most abundant family was Lycosidae (37%; 16 spp.), followed by Gnaphosidae (15%; 10 spp.) and Salticidae (14.5%; 7 spp.). Generalised linear mixed models showed that generic richness was greater in sites with more bare ground. However, this effect was reversed in previously kraaled sites, and was particularly evident for spider abundance that responded negatively relative to unkraaled sites. Furthermore, with a U-shaped recovery, generic richness increased with time since kraaling. Model-based multivariate models showed that short-duration kraaling had a significant impact on spider assemblage structure, but this impact was relatively small compared with the effect of seasonality. Most of the species that made significant contributions to this multivariate response were less abundant in kraaled sites. Spider diversity, therefore, had a weak negative response to short-term kraaling. However, these impacts should also be assessed at broader scales, including areas where cattle go to graze during the day.