Mechanisms of Interference and Foraging Among Colonies of the Harvester ant Pogonomyrmex Californicus in the Mojave Desert

Publisher: John Wiley & Sons Inc

E-ISSN: 1939-9170|60|4|729-737

ISSN: 0012-9658

Source: Ecology, Vol.60, Iss.4, 1979-08, pp. : 729-737

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Abstract

This report examines patterns of competition and foraging dynamics among colonies of the harvester ant Pogonomyrmex californicus. Two components of harvesting efficiency are defined: total harvesting efficiency (i.e., all food items considered) and seed harvesting efficiency (only seeds considered). Throughout the summer, total harvesting efficiency remained constant, whereas seed—harvesting efficiency exhibited an increase as a result of changes in the relative availability of the dominant seed crop, Erodium cicutarium. Several aspects of interference were studied. Colonies were uniformly spaced, and nest relocations significantly increased nearest—neighbor distance. Of encounters between ants from different colonies, 81% resulted in some form of aggression and 7% were fatal to one or both foragers. In a particular study, forager mortality rate was estimated at 0.06 deaths per ant foraging hour, thus indicating that such aggression may have a substantial impact on colony size. Furthermore, following an encounter involving physical struggle, ants returned to and remained in their nests for an extended period of time, thereby reducing seed input to the colony. The above—mentioned components of interference are examined to their potential effects on colony density, distribution, and size.