A small number of workers with specific personality traits perform tool use in ants

Do They Know What They Are Doing? Cognitive Aspects of Rescue Behaviour Directed by Workers of the Red Wood Ant Formica polyctena to Nestmate Victims Entrapped in Artificial Snares

Ant rescue behaviour belongs to the most interesting subcategories of prosocial and altruistic behaviour encountered in the animal world. Several studies suggested that ants are able to identify what exactly restrains the movements of another individual and to direct their rescue behaviour precisely to that object. To shed more light on the question of how precise the identification of the source of restraint of another ant is, we investigated rescue behaviour of red wood ant Formica polyctena workers, using a new version of an artificial snare bioassay in which a nestmate victim bore two wire loops on its body, one (acting as a snare) placed on its petiole and an additional one on its leg. The tested ants did not preferentially direct their rescue behaviour towards the snare. Moreover, the overall strategy adopted by the most active rescuers was not limited to precisely targeted rescue attempts directed towards the snare, but consisted of frequent switching between various subcategories of rescue behaviour. These findings highlight the importance of precise identification of cognitive processes and overall behavioural strategies for better understanding of causal factors underlying animal helping behaviour in light of new facts discovered by testing of various successive research hypotheses.

Group phenotypic composition drives task performances in ants

Differences in individual behaviour within a group can give rise to functional dissimilarities between groups, particularly in social animals. However, how individual behavioural phenotypes translate into the group phenotype remains unclear. Here, we investigate whether individual behavioural type affects group performance in a eusocial species, the ant Aphaenogaster senilis. We measured individual behavioural traits and created groups of workers with similar behavioural type, either high-exploratory or low-exploratory workers. We tested these groups in four different, ecologically relevant, tasks: reaction to an intruder, prey retrieval from a maze, nest relocation and tool use. We show that, compared to groups of low-exploratory workers, groups of high-exploratory workers were more aggressive towards intruders, more efficient in collecting prey, faster in nest relocation and more likely to perform tool use. Our results demonstrate a strong link between individual and collective behaviour in ants. This supports the 'behavioural type hypothesis' for group dynamics, which suggests that an individual's behaviour in a social environment reflects its own behavioural type. The average behavioural phenotype of a group can therefore be predicted from the behavioural types of individual group members.

Object use in insects

Insects are the most diverse group of organisms in the animal kingdom, and some species exhibit complex social behaviors. Although research on insect object use is still in its early stages, insects have already been shown to display rich object-use behaviors. This review focuses on patterns and behavioral flexibility in insect object-use behavior, and the role of cultural evolution in the development of object-use behaviors. Object use in insects is not widespread but has been documented in a diverse set of taxa. Some insects can use objects flexibly and display various object-use patterns. Like mammals and birds, insects use objects in diverse activities, including foraging, predator defense, courtship, and play. Intelligence, pre-existing manipulative behaviors, and anatomical structure affect innovations in object use. In addition, learning and imitation are the main mechanisms underlying the spread of object-use behaviors within populations. Given that insects are one of the major animal groups engaging in object use, studies of insect object use could provide general insights into object use in the animal kingdom.

Ants combine object affordance with latent learning to make efficient foraging decisions

The affordance of an object refers to its functional properties. For example, a bowl has the affordance of holding water, but a sieve does not. Here, we report that ants learn the affordance of a novel object without this attribute being rewarded, and use the memory of this affordance to avoid predicted, but never experienced, crowding. Ants were trained to feeders, which could support either only one ant or many. Two feeders were encountered, each of identical design but differently scented. After training, on the outward journey, half the ants encounter nestmates, which had fed on food matching one of the training feeders. Encountering returning nestmates reduced preference for the feeder matching the scent of the encountered nestmates, but only for ants trained on a limited-access feeder; ants trained on an unlimited feeder were unaffected. In other words, only if ants know that the food access is limited, and receive information that this feeder is heavily visited, do they reduce their preference for this feeder. To achieve this, the ants had to combine memories of the feeders' affordance with the presence of nestmates. Then they had to use semantic knowledge that restricted food access combined with nestmate presence predicts a likelihood of crowding, or a rule such as "if the food is restricted and there are nestmates on the path, go to another food source." Regardless of the mechanism, these results demonstrate that ants latently learn the affordance of their surroundings, an unexpected cognitive ability for an invertebrate.

What is really social about social insect cognition?

It is often assumed that social life imposes specific cognitive demands for animals to communicate, cooperate and compete, ultimately requiring larger brains. The “social brain” hypothesis is supported by data in primates and some other vertebrates, but doubts have been raised over its applicability to other taxa, and in particular insects. Here, we review recent advances in insect cognition research and ask whether we can identify cognitive capacities that are specific to social species. One difficulty involved in testing the social brain hypothesis in insects is that many of the model species used in cognition studies are highly social (eusocial), and comparatively little work has been done in insects that live in less integrated social structures or that are solitary. As more species are studied, it is becoming clear that insects share a rich cognitive repertoire and that these abilities are not directly related to their level of social complexity. Moreover, some of the cognitive mechanisms involved in many social interactions may not differ from those involved in non-social behaviors. We discuss the need for a more comparative and neurobiologically grounded research agenda to better understand the evolution of insect brains and cognition.

Behavioral variation across the days and lives of honey bees

In honey bee colonies, workers generally change tasks with age (from brood care, to nest work, to foraging). While these trends are well established, our understanding of how individuals distribute tasks during a day, and how individuals differ in their lifetime behavioral trajectories, is limited. Here, we use automated tracking to obtain long-term data on 4,100+ bees tracked continuously at 3 Hz, across an entire summer, and use behavioral metrics to compare behavior at different timescales. Considering single days, we describe how bees differ in space use, detection, and movement. Analyzing the behavior exhibited across their entire lives, we find consistent inter-individual differences in the movement characteristics of individuals. Bees also differ in how quickly they transition through behavioral space to ultimately become foragers, with fast-transitioning bees living the shortest lives. Our analysis framework provides a quantitative approach to describe individual behavioral variation within a colony from single days to entire lifetimes.

Surfactant affects the tool use behavior of foraging ants

Surfactants are commonly used in detergents, soaps and agrichemical products. After use, the residual surfactants can be dispersed into environmental compartments, directly or indirectly affecting aquatic and terrestrial organisms. Ants are one of the few insects that are able to make and use tools when foraging for liquid food. However, this unique behavior of ants may be greatly affected by environmental pollutants. Here, we hypothesized that surfactants have adversarial impacts on ant foraging behavior, and tested this hypothesis by investigating the effect of TWEEN 80 (a common nonionic surfactant) on the tool use behavior of black imported fire ants (Solenopsis richteri) when foraging for liquid food (sugar water). Natural pine needles and man-made sponges were provided as tools for ants. The results revealed increasing surfactant concentration induced ants to deposit more tools and caused a higher drowning rate of ants. S. richteri tended to deposit more pine needles and tools of smaller size when exposed to surfactant. Interactions between tool type and surfactant concentration showed significant effects on tool deposition and drowning rate of ants. Addition of surfactant into sugar water increased the drowning rate and reduced the foraging activity and food collection of ant workers, suggesting that surfactant in liquid food can affect the foraging efficiency of ants. However, availability of tools reduced drowning rate and increased sugar water collected compared to without tools. Our results demonstrated that ants can adjust their tool use strategies to manage the foraging risk caused by environmental surfactant, such as increasing the amount and selecting appropriate size of the tools and assembling tools of different structures. Therefore, long-term exposure to surfactants may alter foraging behavior of ants and contribute to evolve new foraging strategy.

When and Why Did Human Brains Decrease in Size? A New Change-Point Analysis and Insights From Brain Evolution in Ants

Human brain size nearly quadrupled in the six million years since Homo last shared a common ancestor with chimpanzees, but human brains are thought to have decreased in volume since the end of the last Ice Age. The timing and reason for this decrease is enigmatic. Here we use change-point analysis to estimate the timing of changes in the rate of hominin brain evolution. We find that hominin brains experienced positive rate changes at 2.1 and 1.5 million years ago, coincident with the early evolution of Homo and technological innovations evident in the archeological record. But we also find that human brain size reduction was surprisingly recent, occurring in the last 3,000 years. Our dating does not support hypotheses concerning brain size reduction as a by-product of body size reduction, a result of a shift to an agricultural diet, or a consequence of self-domestication. We suggest our analysis supports the hypothesis that the recent decrease in brain size may instead result from the externalization of knowledge and advantages of group-level decision-making due in part to the advent of social systems of distributed cognition and the storage and sharing of information. Humans live in social groups in which multiple brains contribute to the emergence of collective intelligence. Although difficult to study in the deep history of Homo, the impacts of group size, social organization, collective intelligence and other potential selective forces on brain evolution can be elucidated using ants as models. The remarkable ecological diversity of ants and their species richness encompasses forms convergent in aspects of human sociality, including large group size, agrarian life histories, division of labor, and collective cognition. Ants provide a wide range of social systems to generate and test hypotheses concerning brain size enlargement or reduction and aid in interpreting patterns of brain evolution identified in humans. Although humans and ants represent very different routes in social and cognitive evolution, the insights ants offer can broadly inform us of the selective forces that influence brain size.

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

The paper is devoted to analyzing consistent individual differences in behavior, also known as “personalities,” in the context of a vital ant task—the detection and transportation of food. I am trying to elucidate the extent to which collective cognition is individual-based and whether a single individual’s actions can suffice to direct the entire colony or colony units. The review analyzes personalities in various insects with different life cycles and provides new insights into the role of individuals in directing group actions in ants. Although it is widely accepted that, in eusocial insects, colony personality emerges from the workers’ personalities, there are only a few examples of investigations of personality at the individual level. The central question of the review is how the distribution of behavioral types and cognitive responsibilities within ant colonies depends on a species’ foraging style. In the context of how workers’ behavioral traits display during foraging, a crucial question is what makes an ant a scout that discovers a new food source and mobilizes its nestmates. In mass recruiting, tandem-running, and even in group-recruiting species displaying leadership, the division of labor between scouts and recruits appears to be ephemeral. There is only little, if any, evidence of ants’ careers and behavioral consistency as leaders. Personal traits characterize groups of individuals at the colony level but not performers of functional roles during foraging. The leader-scouting seems to be the only known system that is based on a consistent personal difference between scouting and foraging individuals.