Temporal variation in recognition cues: implications for the social life of weaver ants Oecophylla smaragdina

Recognition systems are involved in a range of evolutionary and biological processes, and animals use a variety of visual, auditory, tactile and olfactory cues to determine the status of others. The use of chemical cues is widespread, occurring among mammals, fish, reptiles and birds, but particularly among insects. Yet chemical cues may be influenced by diet and environment, and can change over time, potentially limiting their reliability as recognition cues. Nevertheless, they play a key role in colonymate recognition among social insects. We created colony isolates from large multinest colonies of weaver ants and asked (1) whether colony spectral profiles (determined using near-infrared spectroscopy) changed over time, (2) whether spectral profiles of colony isolates diverged from those of original colonies, and (3) whether the behaviour of original colonies towards colony isolates changed over time. Although we detected changes in the spectral profile of original colonies and colony isolates, they did not diverge significantly from each other. As far as we are aware, this is the first time that such parallel changes in colony odour have been observed. Aggression towards individuals from colony isolates did not increase, although levels of trophallaxis did. This demonstrates that colonymate recognition among weaver ants was unimpaired by temporal variation in recognition cues. We discuss the characteristics of weaver ants that might give rise to this system. We also discuss the implications for other organisms when, for example, ontogenetic changes in the expression of individual cues may hamper their usefulness as kin recognition cues.