The adaptive significance of social information in tandem-running ants
Evolution, Anthropology
Final Report Abstract
Social learning is widespread in nature and plays an important role in the acquisition of locally adaptive behaviours in many animals. Yet, it is still poorly understood why and when social learning is more beneficial than individual learning. While social learning can provide a lowcost, low-risk strategy to acquire information, it is also prone to acquiring outdated, unreliable and even maladaptive information. In a simulation study published in Science, Rendell et al. (2010) tested the success of different learning strategies in varying environments and found that social learning leads to greater rewards than individual learning in almost all ecological situations. These results challenge the widespread believe that animals should follow mixed strategies and they contradict the assumption that a pitfall of social learning is the acquisition of low-quality information. Communication in social insects has been studied since more than a century, but only recently have insights been viewed in the light of social learning theory. Many ant species use a form of recruitment called ‘tandem running’, whereby an informed individual guides an uninformed nestmate to a resource. Tandem running is currently the only known example of ‘teaching’ in non-mammals and represents a promising behaviour to study the benefits of social information at both individual and colony level. This project tested predictions of social learning theory, in particular the prediction from the Rendell et al. (2010) model that social learning leads to better rewards than individual learning. Using Temnothorax nylanderi as a model species for laboratory experiments, we found that social learning leads to better rewards only in some environments, namely when food sources are plentiful. Individual learners were able to improve their rewards through a strategy of frequent food source switching. We used the Neotropical ponerine ant Pachycondyla harpax to study the value of social learning under field conditions in Brazil and found support for the prediction that tandem communication increases the rewards of individual ants and colonies because it allows colonies to establish a critical mass of individuals at food sources, which they can then defend against competitors. A simulation modelling approach confirmed that the spatio-temporal distribution of food sources affects the value of communication and identified colony size as a critical driver of the value of social learning. Surprisingly, only in colonies above a certain size does social learning improve colony foraging success. One reason for the finding that social learning via tandem running is not always beneficial is that tandem running has considerable time and opportunity costs, mainly because social learners, unlike individual learners, have to wait for social information. We provide further evidence that tandem runs often fail and identify body size differences between the teacher and the pupil (social learner) as a key reason for failed tandem runs. These findings improve our understanding of the adaptive value of social information in tandem running ants and help us to better understand the circumstances the favour the evolution of communication about resources in social insects.
Publications
- (2018) Ants (Temnothorax nylanderi) adjust tandem running when food source distance exposes them to greater risks. Behavioral Ecology and Sociobiology 72:40
Glaser S, Grüter C
(See online at https://doi.org/10.1007/s00265-018-2453-2) - Nascimento FS (2018) Tandem recruitment and foraging in the ponerine ant Pachycondyla harpax (Fabricius). Neotropical Entomology 47:742–749
Grüter C, Wüst M, Cipriano AP
(See online at https://doi.org/10.1007/s13744-017-0571-6) - (2021) Large body size variation is associated with low communication success in tandem running ants. Behavioral Ecology and Sociobiology 75:4.
Wagner T, Bachenberg L, Glaser SM, Oikonomou A, Linn M, Grüter C
(See online at https://doi.org/10.1007/s00265-020-02941-x) - (2021) Tandem communication improves ant foraging success in a highly competitive tropical habitat. Insect Sociaux
Glaser SM, Feitosa RM, Koch A, Goß N, do Nascimento FS, Grüter C
(See online at https://doi.org/10.1007/s00040-021-00810-y) - (2021) The adaptive value of tandem communication in ants: insights from an agent-based model. Journal of Theoretical Biology
Goy N, Glaser SM, Grüter C
(See online at https://doi.org/10.1016/j.jtbi.2021.110762)
