Temporal and spatial patterns of foraging in two syntopic ant species, Manica yessensis and Formica lemani, on Mount Fuji, Japan

Spatiotemporal characteristics of terrestrial foraging were studied in two ant species, Manica yessensis and Formica lemani, in a volcanic desert on the southeast slope of Mount Fuji, Gotenba, Japan. Both ants are common in this habitat, and they construct underground nests in this dry area with sparse vegetation. Nests of M. yessensis have multiple nest-openings on the surface, whereas nests of F. lemani have very few openings, but their nesting and foraging areas overlap completely. A “mark-and-observe” method applied to M. yessensis demonstrated that worker ants of this species move between openings more than 3 m away. A study plot (6 m × 12 m quadrat) was set up, in which all nest-openings of both species were mapped. Day-long observations on numbers of foragers in this plot revealed that foraging M. yessensis are active in morning and evening, while F. lemani continues foraging all day, but both species cease activity at night. Associations between locations of foragers and nest-openings differed significantly between the two species, that is, surface foraging of M. yessensis workers was largely confined to the vicinity of their nest-openings, whereas foragers of F. lemani travelled far from their nest-openings. The function of multiple nest-openings in M. yessensis is discussed.