Spatial distribution, mobility, gregariousness, and defensive behaviour in a Brazilian cave harvestman Goniosoma albiscriptum (Arachnida, Opiliones, Gonyleptidae)

This study provides information on population dynamics and behaviour (gregariousness and defensive tactics) of the Brazilian cave harvestman Goniosoma albiscriptum (Goniosomatinae). Through a mark-recapture study, we observed that this species regularly uses the cave during the day, leaving it to forage on the vegetation after dusk (i. e., a trogloxene species). There were nine groups within the cave, composed of females and males, the latter being the only sex that moved from one group to another (although rarely). Distinct groups used distinct openings of the cave to leave the shelter after dusk. Goniosoma albiscriptum showed a variety of mechanical defensive behaviours, and also exuded scent gland secretions. During dryer and colder months (between April and August), adult and subadult harvestmen aggregated on the cave walls. The individuals that composed the aggregations were not always the same ones. Reproductive activity (detected by the presence of egg batches) was negatively correlated with formation of aggregations. We suggest that intolerance towards conspecifics during the reproductive period may inhibit the formation of aggregations.