Red Wood Ants Display Natural Aversive Learning Differently Depending on Their Task Specialization

Abstract

The adaptive benefits of individual specialization and how learning abilities correlate with task performance are still far from being well-understood. Red wood ants are characterized by their huge colonies and deep professional specialization. We hypothesized that red wood ants Formica aquilonia form aversive learning after having negative encounters with hoverfly larvae differently, depending on their task specialization. We tested this hypothesis, first, by examining whether hunters and aphid milkers learn differently to avoid the nuisance of contacts with syrphid larvae, and, second, by analyzing the difference between learning in “field” and laboratory-reared (naïve) foragers. During the first interaction with the syrphid larva in their lives the naïve foragers showed a significantly higher level of aggressiveness than the members of a natural colony. Naïve foragers applied the “mortal grip,” “prolonged bites,” and “nibbling” toward the enemy with a significantly higher frequency, whereas members of both “field” groups behaved more carefully and tried to avoid encounters with the larva. The aphid milkers, who had a negative experience of interaction with the larva, being “glued” with its viscous secretion, behaved much less aggressively in the follow-up experiments after 10 min and even 3 days, thus exhibiting the shaping of both short- and long-term memories. However, both “field” hunters and naïve foragers demonstrated no signs of aversive learning. These data provide some new insights into the relationship between task specialization and learning performance in ants. Given our previous results, we speculate that scouts and aphid milkers are the most cognitively gifted specialists in red wood ants, whereas hunters and guards are rather brave than smart.

Ants’ Personality and Its Dependence on Foraging Styles: Research Perspectives

“…For example, some species exhibit age-related repertoire expansion, whereas, in others, workers of certain ages have strong tendencies to perform specific tasks (reviews in Hölldobler and Wilson, 2009;Giraldo and Traniello, 2014). In other species, task specialization among workers may be shaped by their size polymorphism, genetic background, experience, and social interactions, which is also partly influenced by age (review in Iakovlev and Reznikova, 2019). The allocation of workers to various tasks may depend on external cues, such as interactions among ants and changes in the environment (Gordon, 2016).…”

“…Experiments with other intruders, such as spiders and parasitic rove beetle, revealed a context-dependent specialization in colony defense in F. rufa: small workers were better at preventing brood predation than larger workers, and nurses and workers at nest entrances were more aggressive toward parasitic beetles than foragers (Parmentier et al, 2015). Recently, Iakovlev and Reznikova (2019) showed that in red wood ants F. aquilonia, members of various professional groups form aversive associations with different strengths and speeds. The authors examined whether hunters and aphid milkers learn to avoid the irritating encounters with their enemy (hoverfly larvae) differently.…”

“…They found striking consistent individual variation in cognitive performance among wild rodents. Carpenter ants display consistent cognitive variability linked to individual peculiarities in exploratory activity (d 'Ettorre et al, 2017); red wood ants demonstrate stable differences in their ability to form aversive learning after having negative encounters with their eternal enemy (hoverfly larvae), depending on their role in society (Iakovlev and Reznikova, 2019; see details in the next sections).…”

Regulation of Ant Foraging: A Review of the Role of Information Use and Personality

“…These individuals should also have more flexible learning abilities and rely more on personal information. Foragers who vary in their foraging strategies as in Ectatomma ruidum (McGlynn et al, 2015) or in their resource specialization as in Formica aquilonia (Iakovlev and Reznikova, 2019) should also vary in their personality traits and cognitive abilities. Since the task repertoire of individual ants changes with age, further studies are also required to understand whether personality traits of individuals remain constant across their lifetimes and how this affects their task choice and task performance at different stages of their life.…”