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Diurnal and nocturnal foraging specialisation in Neotropical army ants

Abstract:

Temporal segregation of species' activity periods may lessen interspecific competition. e tested for temporal segregation among Neotropical army ants (Formicidae: Dorylinae). Co-occurring species overlap on prey resources, and regular colony movements and long-distance raiding increase interspecific interference. We hypothesised interspecific competition selects for temporal separation of species' raid periods into diurnal versus nocturnal activity. We pbkp_redicted species would differ significantly in their timing of foraging. We further pbkp_redicted timing would differ among congeners because close relatives likely overlap in resource needs. Trail walk encounter rates were used to estimate species' diurnal versus nocturnal foraging activity at four Neotropical sites. Army ant species differed significantly in foraging times. There were significantly diurnal and nocturnal specialists; some species foraged at similar rates day and night. Two genera (Eciton and Neivamyrmex) included both diurnal and nocturnal specialists. Relative eye size (a morphological indicator of above-ground activity) was positively associated with diel foraging specialisation (both diurnal and nocturnal). Temporal separation of foraging times may play a role in allowing Neotropical army ant species to occupy the same habitat. Diel specialisation may be a common mechanism for species coexistence in tropical forests where season-based phenological changes are often moderated.