Measurement of spatial behavior: methodology applied to rhesus monkeys, neon tetras, communal and solitary spiders, cockroaches, and gnats in open fields

Abstract

The comparison of spacing patterns between animal groups is made possible by a methodology which uses the following steps: Members of a group are photographed from above, animal position coordinates are extracted from photographs, and 10 objective measures of distance or distribution are computed. Six group-living species with different life-styles were compared in replicate groups: rhesus monkeys, neon tetra fish, communal spiders Mallos gregalis , funnel web spiders Agelenopsis utahena , American cockroaches, and eye gnats. Groups of 25 individuals were released into open-field arenas scaled to the animals' size. Photographic intervals were computed according to the motility of each species. Spacing measures were contrasted between replicate groups and each species was compared to an inanimate control model. Every species showed significant active spatial behavior in three or more measures. Replicates adhered to general species patterns and some group-typical spacing values were found. Three general patterns of spacing were present: spatial subgroups of 3–4 members in monkeys and communal spiders (most interactive groups); more homogeneous, significant aggregation in neon tetras and cockroaches (less interactive groups); and uniform distance spacing in funnel web spiders and eye gnats (predominantly solitary life-style). Applications for future studies, behavioral mechanisms, and group spacing theory are discussed.