ABSTRACT
Aggression has multiple benefits and is often coupled with other behaviors ("behavioral syndromes"). The level of aggressiveness is influenced by an adaptive benefit-cost ratio suggesting that benefits should outweigh the costs of aggression. Here, we assess if several behaviors are coupled in two behaviorally different populations (aggressive, peaceful) of the high-elevation ant Tetramorium alpestre. For three weeks, we collected colony fragments and analyzed boldness, exploring, foraging, and risk-taking behaviors. We hypothesized that the aggressive population is bolder, more explorative and risk-prone, and forages more food than the peaceful population. To test whether (a) the combination of experiments and parameters used yields a good setup, (b) populations differ behaviorally, and (c) populations display behavioral syndromes, we assessed (a) the frequency of repeatable behaviors of each experiment, (b) the behavioral means among populations, and (c) the behavioral repeatability, respectively. We found that (a) boldness and exploring were most repeatable and represent a good experimental setup, (b) the aggressive population was bolder and more explorative and risk-prone than the peaceful population, (c) boldness and exploring behaviors were highly repeatable in both populations, thus corroborating our hypothesis. The results suggest that boldness, exploring, and risk-taking but not foraging are presumably coupled with aggression and indicate the presence of behavioral syndromes in this ant. Under specific ecological conditions, aggression may be coupled with other behaviors and important for finding food. Aggression is probably adaptive in T. alpestre, possibly indicating that selection favors aggression at least partially, which may counteract the complete loss of intraspecific aggression.
ABSTRACT
Standardised assays are often used to characterise aggression in animals. In ants, such assays can be applied at several organisational levels (e.g., colony, population) and at specific times during the season. However, whether the behaviour differs at these levels and changes over a few weeks remains largely unexplored. Here, six colonies from the high-elevation ant Tetramorium alpestre were collected weekly for five weeks from two behaviourally-different populations (aggressive and peaceful in intraspecific encounters). We conducted one-on-one worker encounters at the colony and population levels. When analysing the colony combinations separately, the behaviour was peaceful and remained so within the peaceful population; initial aggression became partially peaceful within the aggressive population; and initial aggression decreased occasionally and increased in one combination but remained constant for most across-population combinations. When analysing all colony combinations together, within-population behaviour remained similar, but across-population behaviour became peaceful. The observed behavioural differences among organisational levels emphasise the relevance of assessing both levels. Moreover, the effect of decreasing aggression is discernible already over a few weeks. Compression of the vegetation period at high elevations may compress such behavioural changes. Addressing both organisational levels and seasonality is important, particularly in studies of behavioural complexity such as in this ant.
