Biomedical subjects

G Theraulaz

Publications and source records attributed to G Theraulaz.

7 recordsLinked to original sources

PubMed2005

A new test of random walks in heterogeneous environments.

Environmental heterogeneities can change animal movement in two different manners. First, they can modify movement characteristics (move lengths or turning angles), in which case the movement remains of the diffusive kind. Second, they can bias displacement towards a particular direction in which case it becomes non-diffusive. We propose in this paper a simple method that only requires computing the mean length of a sample of trajectories in some bounded area to distinguish between these two kinds of movement. We show through simulations that the method allows to detect the presence of heterogeneities that orient animal movement. We apply it to experimental trajectories of Messor sancta ants engaged in corpse aggregation to show that their displacement is oriented at the contact of the formed corpse piles and that their trajectories become non-diffusive.

Animals↗

PubMed2001

Model of droplet dynamics in the Argentine ant Linepithema Humile (Mayr).

The formation of droplets of ants Linepithema humile (Mayr) is observed under certain experimental conditions: a fluctuating aggregate forms at the end of a rod and a droplet containing up to 40 ants eventually falls down. When the flux of incoming ants is sufficient, this process can continue for several hours, leading to the formation and fall of tens of droplets. Previous work indicates that the time series of drop-to-drop intervals may result from a nonlinear low-dimensional dynamics, and the interdrop increments exhibit long-range anticorrelations. A model of aggregation and droplet formation, based on experimental observations, is introduced and shown to reproduce these properties.

Animals↗

PubMed2000

Inspiration for optimization from social insect behaviour.

Research in social insect behaviour has provided computer scientists with powerful methods for designing distributed control and optimization algorithms. These techniques are being applied successfully to a variety of scientific and engineering problems. In addition to achieving good performance on a wide spectrum of 'static' problems, such techniques tend to exhibit a high degree of flexibility and robustness in a dynamic environment.

Algorithms↗

PubMed2000

Three-dimensional architectures grown by simple 'stigmergic' agents.

A simple model of multi-agent three-dimensional construction is presented. The properties of this model are investigated. Based on these properties, a fitness function is defined to characterize the structured patterns that can be generated by the model. The fitness function assigns a value to each pattern. The choice of the fitness function is validated by the fact that human observers tend to view patterns with high (resp. low) fitness as structured (resp. unstructured). A genetic algorithm based on this fitness function is used to explore the space of possible patterns. The genetic algorithm is able to make use of sub-modules of existing patterns and recombine them to produce novel patterns, but strong epistatic interactions among genes make the fitness landscape rugged and prevent more complex patterns from being produced.

Algorithms↗

PubMed1999

A brief history of stigmergy.

Stigmergy is a class of mechanisms that mediate animal-animal interactions. Its introduction in 1959 by Pierre-Paul Grassé made it possible to explain what had been until then considered paradoxical observations: In an insect society individuals work as if they were alone while their collective activities appear to be coordinated. In this article we describe the history of stigmergy in the context of social insects and discuss the general properties of two distinct stigmergic mechanisms: quantitative stigmergy and qualitative stigmergy.

Animals↗

PubMed1998

Group and mass recruitment in ant colonies: the influence of contact rates

The influence of contact rates on the efficiency (the ability to exploit a profitable environment) and flexibility (the ability to track down a changing environment) of foraging in ants is studied theoretically in the case where foraging relies on a mixture of group and mass recruitment. It is shown that a combination of efficiency and flexibility can be reached across a range of group sizes if (1) mass recruitment is combined with a low level of group recruitment, and (2) contact rates are weakly regulated. These results are discussed in relation to empirical work. Copyright 1998 Academic Press

Journal Article↗

PubMed1998

The synchronization of recruitment-based activities in ants.

A simple model of recruitment-based foraging in ants illustrates the idea that synchronized patterns of activity can endow a colony with the ability to forage more efficiently when a minimal number of active individuals is required to establish and maintain food source exploitation. This model, which can be extended to other activities that involve recruitment, may help explain why bursts of synchronization have been observed in several species of ants.

Animals↗