Factors that affect the occupancy, activity and distribution patterns of Grammostola vachoni, an endemic tarantula from the austral mountains of Argentina

Abstract

Activity and occupancy dynamics of spiders are topics that have received little attention and are compounded by anecdotal field data, especially in Theraphosidae that are generally nocturnal. Due to potential vulnerability outside their burrows, it is expected that individuals remain in the safety of their shelters most of the time and because their limited dispersal mechanism, usually by walking over short distances. Grammostola vachoni is an endemic tarantula from Argentina listed as Vulnerable specie by the IUCN. Changes in natural habitat of G. vachoni are detrimental for their survivorship. However, little is known about whether their occupancy dynamics and spatial distribution pattern are affected by different disturbances. In this study we evaluated whether disturbances in the natural habitat of G. vachoni affected the distribution patterns and adults abundance in different populations and determined activity patterns and refuge fidelity. It was observed that the spiders emerged after 9:30 pm and showed an exploratory behavior; females exhibited high refuge fidelity. Results showed that in disturbed habitats the spiders presented an aggregated distribution, whereas in undisturbed habitats spiders remained in settlements with greater distances between neighbors. Therefore, it can be concluded that the distribution patterns of G. vachoni are influenced by environmental disturbances to their natural habitat. These aspects are particularly important due to the conservation status of the spider, since the continual regression of mountain grassland in Argentina puts species viability at risk; especially in species with limited dispersal capability, a longer life cycle and sedentary habits such as G. vachoni.