Foraging Behavior of Competing Africanized Honeybees and Stingless Bees

Abstract

The colonizing success and potential influence of immigrant Africanized honeybees in the neotropics depends on their foraging style and competitive ability. Experiments were performed to compare the foraging tactics of this invading species to those of its most abundant competitors, highly social stingless bees of the genera Melipona and Trigona. In an area containing a rich assemblage of stingless bees in French Guiana, Africanized honeybees were significantly more abundant on honey—water feeders during a high "nectar flow" period than combined stingless bee and wasp species. During the last 15 min of the experiments, when bait was not replenished on feeders, Africanized honeybees abandoned the feeders but native foragers continued to arrive. None of the stingless bees, including four aggressive Trigona, displaced from the feeders the foragers of several (two to seven) colonies of Africanized honeybees. The cost of attacking Africanized honeybees at feeders apparently exceeded the benefit for large, aggressive Trigona williana and T. hyalinata branneri. These bees abandoned feeders visited by nonaggressive Africanized honeybees. Single, small Africanized honeybee colonies were displaced from feeders by aggressive foragers of T. Pallens pallens and T. h. branneri. In one instance Africanized honeybeeys shifted almost immediately to a floral resource, while abandonment of the feeders by T. williana was not followed by a shift to a natural food source. Reduction of competitive interaction with Africanized honeybees was accomplished by foragers of T. clavipes and T. p. pallens that partitioned four feeders by visiting only two, leaving the other to Africanized bees. Interspecific displacement was never absolute; a few foragers from a displaced colony always visited the feeders. Africanized honeybees and Melipona fulva foraged nonaggressively both at feeders and flowers, but Africanized bees at feeders exhibited low levels of aggression toward Melipona and polybiine wasps on one occasion. Unlike other aggressive Trigona, T. clavipes was at times unaggressive. Colonies of T. h. branneri and Africanized honeybees, the bees most successful in displacing other species from feeders, were comprised of many more workers than colonies of the other bees. The combined advantages of (1) the ability to communicate the distance and direction of a food source from the nest, (2) large forager size, and (3) large colony size provide Africanized honeybee colonies with a competitive ability superior to that of stingless bees at rich, compact resources.