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Pratt, S. C.

Publications and source records attributed to Pratt, S. C..

8 recordsLinked to original sources
bioRxiv2022

Cryptic functional diversity in ant tandem runs

Ants have evolved diverse recruitment methods to guide colony members to valuable resources, such as food or nest sites. One of these methods, tandem running, consists of an informed leader directly guiding a naive follower every step of the way from nest to resource. Although this behavior appears superficially similar in the different ant taxa in which it has independently evolved, this similarity could conceal underlying functional and mechanistic differences. Here we present a combined network and information-theoretic analysis, which reveals fundamental differences in the tandem recruitment between two distantly related ant genera, Temnothorax and Diacamma. Temnothorax uses tandem running to recruit additional recruiters, whereas Diacamma uses it principally to move the passive majority of the colony, a task that Temnothorax accomplishes with a different behavior, social carrying. Accordingly, the structure of the tandem run recruitment networks of Diacamma was different from those of Temnothorax, with Diacamma networks more closely resembling the social carrying networks of Temnothorax. Furthermore, an information-theoretic analysis of the spatial trajectories of leaders and followers revealed that Diacamma tandem runs lack bidirectional information flow, the signature of route-learning in Temnothorax tandem runs. These results suggest that Diacamma uses tandem runs not to share information, but to transport nestmates. By quantifying the cryptic diversity of communication behavior, this study increases the resolution of our understanding of animal societies.

animal behavior and cognition↗
bioRxiv2022

Weaver ants regulate the rate of prey delivery during collective vertical transport

The collective transport of massive food items by ant teams is a striking example of biological cooperation, but it remains unclear how these decentralized teams coordinate to overcome the various challenges associated with transport. Previous research has focused on transport across horizontal surfaces and very shallow inclines, disregarding the complexity of natural foraging environments. In the ant Oecophylla smaragdina, prey are routinely carried up tree trunks to arboreal nests. Using this species, we induce collective transport over a variety of angled surfaces with varying prey masses to investigate how ants respond to inclines. We found that weight and incline pose qualitatively different challenges during transport. Prey were carried over vertical inclines faster than across horizontal surfaces even though inclines were associated with longer routes and a higher probability of dropping the load. This additional speed is associated with more transporters being allocated to vertical loads and not from the persistence of individual ants. Ant teams also regulated a stable "prey delivery rate" (rate of return per transporter) across all treatments. Our proposed constrained optimization model explains these results: prey intake rate at the colony level is maximized when the allocation of transporters yields a similar prey delivery rate across loads.

animal behavior and cognition↗
bioRxiv2021

Naïve individuals promote collective exploration in homing pigeons

Group-living animals that rely on stable foraging or migratory routes can develop behavioural traditions to pass route information down to inexperienced individuals. Striking a balance between exploitation of social information and exploration for better alternatives is essential to prevent the spread of maladaptive traditions. We investigated this balance during cumulative route development in the homing pigeon Columba livia. We quantified information transfer within pairs of birds in a transmission-chain experiment and determined how birds with different levels of experience contributed to the exploration- exploitation trade-off. Newly introduced naive individuals were initially more likely to initiate exploration than experienced birds, but the pair soon settled into a pattern of alternating leadership with both birds contributing equally. Experimental pairs showed an oscillating pattern of exploration over generations that might facilitate the discovery of more efficient routes. Our results introduce a new perspective on the roles of leadership and information pooling in the context of collective learning.

animal behavior and cognition↗
bioRxiv2021

Coordination of movement via complementary interactions of leaders and followers in termite mating pairs

Leadership of animal group movements depends on social feedback, hence leaders signals and followers responses should be attuned to each other. However, leader and follower roles are difficult to disentangle in species with high levels of coordination. To overcome this challenge, we investigated a simple case of movement coordination: termite pairs in which a female leads a male as they search for a nest site. To tease apart leader and follower roles, we created conspecific and heterospecific pairs of Coptotermes gestroi and C. formosanus, which share a pairing pheromone so that males follow females of either species. Conspecific pairs were stable for both species, even though C. gestroi females produce less pheromone than C. formosanus. Heterospecific pairs with C. gestroi males were also stable, but not those with C. formosanus males. We attributed this difference to the C. gestroi males unique capacity to follow females that release small amounts of pheromone; C. formosanus males cannot follow or reject C. gestroi females as unsuitable. This conclusion was supported by an information-theoretic analysis that detected information flow from C. formosanus females to C. gestroi males as in conspecific pairs, but not from C. gestroi females to C. formosanus males. Despite their following ability, C. gestroi males lost to C. formosanus males in competitions to follow C. formosanus females. Thus, partner selection has shaped the species-specific association of mating pairs. Our results demonstrate that a similar level of coordination can emerge from distinct sets of complementary sender-receiver interactions.

animal behavior and cognition↗
bioRxiv2020

A Comprehensive and Predictive Agent-based Model for Collective House-Hunting in Ant Colonies

The decentralized cognition of animal groups is both a challenging biological problem and a potential basis for bio-inspired design. The understanding of these systems and their application can benefit from modeling and analysis of the underlying algorithms. In this study, we define a modeling framework that can be used to formally represent all components of such algorithms. As an example application of the framework, we adapt to it the much-studied house-hunting algorithm used by emigrating colonies of Temnothorax ants to reach consensus on a new nest. We provide a Python simulator that encodes accurate individual behavior rules and produces simulated behaviors consistent with empirical observations, on both the individual and group levels. Critically, through multiple simulated experiments, our results highlight the value of individual sensitivity to site population in ensuring consensus. With the help of this social information, our model successfully reproduces experimental results showing the high cognitive capacity of colonies and their rational time investment during decision-making, and also predicts the pros and cons of social information with regard to the colonies ability to avoid and repair splits. Additionally, we use the model to make new predictions about several unstudied aspects of emigration behavior. Our results indicate a more complex relationship between individual behavior and the speed/accuracy trade-off than previously appreciated. The model proved relatively weak at resolving colony divisions among multiple sites, suggesting either limits to the ants ability to reach consensus, or an aspect of their behavior not captured in our model. It is our hope that these insights and predictions can inspire further research from both the biology and computer science community.

animal behavior and cognition↗
bioRxiv2019

Parameter tuning facilitates the evolution of diverse tunneling patterns in termites

The nest structures built by social insects are complex group-level patterns that emerge from interactions among individuals following simple behavioral rules. The theory of complex systems predicts that there is no simple one-to-one relationship between variations in collective patterns and variation in individual behaviors; therefore, it is essential to know how actual behavior evolves to change pattern formation. Here we demonstrate that the evolutionary divergence of termite tunneling patterns is achieved by quantitative tuning of shared behavioral rules, rather than the acquisition of novel behaviors. We compared tunnel formation between two closely related species, Reticulitermes tibialis and Heterotermes aureus, and found that H. aureus builds more highly branched tunnels than R. tibialis. Our behavioral analysis and data-based modeling revealed that these species share the same behavioral repertoire, but a quantitative difference in the probability of sidewall excavation leads to diverse tunneling patterns. In contrast, we also found that Paraneotermes simplicicornis, which evolved tunneling independently, possesses a distinct behavioral repertoire, but shows convergence of branching patterns with R. tibialis. These results elucidate the complex relationship between individual behavior and group-level patterns; in some cases, distinct behavioral rules can produce similar group-level patterns, but in others, a common rule set can yield distinct patterns via parameter tuning. The evolutionary process of collective behavior is flexible and much more complex than we can infer from group-level patterns alone.

animal behavior and cognition↗
bioRxiv2019

Division of labor promotes the spread of information in colony emigrations by the ant Temnothorax rugatulus

The fitness of group-living animals often depends on how well members share information needed for collective decision-making. Theoretical studies have shown that collective choices can emerge in a homogeneous group of individuals following identical rules, but real animals show much evidence for heterogeneity in the degree and nature of their contribution to group decisions. In social insects, for example, the transmission and processing of information is influenced by a well-organized division of labour. Studies that accurately quantify how this behavioural heterogeneity affects the spread of information among group members are still lacking. In this paper, we look at nest choices during colony emigrations of the ant Temnothorax rugatulus and quantify the degree of behavioural heterogeneity of workers. Using methods from both machine learning and network analysis, we identify and characterize four behavioural castes of workers - primary, secondary, passive, and wandering - covering distinct roles in the spread of information during each emigration. This detailed characterization of the contribution of each worker can improve models of collective decision-making in this species and promises a deeper understanding of behavioural variation at the colony level.

animal behavior and cognition↗
bioRxiv2019

Ants acknowledge information to control its rate of transfer

Behavioral correlations stretching over time are an essential but often neglected aspect of interactions among animals. These correlations pose a challenge to current behavioral-analysis methods that lack effective means to analyze complex series of interactions. Here we show that non-invasive information-theoretic tools can be used to reveal communication protocols that guide complex social interactions by measuring simultaneous flows of different types of information between subjects. We demonstrate this approach by showing that the tandem-running behavior of the ant Temnothorax rugatulus and that of the termites Coptotermes formosanus and Reticulitermes speratus are governed by different communication protocols. Our discovery reconciles the diverse ultimate causes of tandem running across these two taxa with their apparently similar signaling mechanisms. We show that bidirectional flow of information is present only in ants and is consistent with the use of acknowledgement signals to regulate the flow of directional information.

animal behavior and cognition↗