Territory Size and Population Limits in Mangrove Termites

Abstract

(1) We examined territory size in the termites Nasutitermes nigriceps and N. corniger in mangrove forests on the Atlantic coast of Panama. Foraging areas in these species were defended intra- and interspecifically. (2) Habitat structure strongly affected territory size. Where prop roots of the red mangrove, Rhizophora mangle, provided connections between trees, territories could grow to enormous sizes (range: 1-1750 m2), and many colonies bordered neighbours along the perimeters of their foraging areas. Large battles occasionally broke out at points of contact. (3) Where R. mangle was absent, lack of connections between trees limited territory area, in mapped plots, to one or two trees (range: 1-110 m2), and many apparently suitable areas remained unoccupied. Colonies given artificial connections to neighbouring trees were more likely to expand than unmanipulated controls. (4) In forests with R. mangle, territory size and nest volume were highly correlated. The relationship was nearly linear, suggesting that the biomass of termites supported per unit area of forest was independent of territory size. An increase of one litre in nest volume was associated with an increase of 3.77 m2 in foraging area. (5) The effects of territoriality in populations of social insects are contrasted with those in populations of solitary, mobile animals. In populations of social insects, territorial aggression mediates the growth of colonies at the expense of neighbours. The limit to population growth imposed is not a maximum density of colonies, but is instead a combined function of colony biomass and density.