The walking male: activity, locomotor performance and influence of climate in movement of males of an endangered tarantula (Grammostola vachoni) over the reproductive season

Abstract

In tarantulas, the reproductive season in their natural habitat is characterized by the presence of walking males. Grammostola vachoni is a tarantula from Argentina, and previous studies have reported that the breeding season occurs only in spring. However, walking males are also observed in other months. Thus, our objectives here were to study the dynamics of G. vachoni in the reproductive season, to compare male activity with climate data and to estimate whether temperature affects male locomotor performance. Two peaks of walking male activity were found (from the end of October to December, and in March). The number of walking females registered was low and was also bimodal. No significant differences between the sexes in activity with regard to temperature and atmospheric pressure were observed, but females were more likely to be observed under the highest humidity conditions. The months of the reproductive season were very similar in their climate characteristics. Male locomotor performance was strongly affected by extreme temperatures, and the optimum experimental temperature was higher than the environmental activity temperature. This study suggests a diplochronous cycle for G. vachoni, which might be a historical constraint or might indicate selection.