If you would like to meet with ACCS visitors, Jérôme Buhl and/or Audrey Dussutour, please contact Jim Hanan: jim@maths.uq.edu.au.
----------------------------------
'Seminar: Thursday 23 November, 10:30 Morning Tea, 11:00am seminar
Place: Room 621/622, GP South (Building 78)
Speaker: Audrey Dussutour, Postdoctoral Fellow, School of
Biological Sciences, University of Sydney
www.audrey-dussutour.net/CVaudrey-dussutour.html
Title: "Moving in the crowd: Ants hold the key to
traffic chaos."
Abstract:
The collective displacement of assemblies of organisms is
certainly one of the most spectacular phenomena one can
observe in nature. A column of army ants, a swarm of
locusts, a herd of migrating wildebeests, a flock of birds
or a shoal of fish can sometimes comprise several millions
of individuals. Collective displacements are characterized
by a high degree of coordination among individuals. A higher
proximity between individuals is generally beneficial,
because it promotes cooperation by facilitating the
exchanges of information that is essential for the
maintenance of group cohesion. Too much proximity however
can lead to a high concentration of individuals. Detrimental
effects may then occur and lead to a failure in the
functioning of the group, which will affect the individuals
in turn. In extreme cases, a high density may even lead to a
total standstill of group activity.
Ants provide an excellent model for the study of collective
movement because of their highly social organization that
functions in a completely decentralized manner.
My work deals with the organization of collective movements
in ants in presence of environmental heterogeneities,
particularly in situations involving crowding. We chose two
species of ants, characterized by different degrees of
polymorphism, as well as by their mode of food transport.
Our aim is to identify the link between the behavioral rules
observed at the scale of the individual and the spatio-temporal
organization observed at the scale of the group.
Independently of the species, we found that the regulation
of traffic in crowding situations depends both on
interattraction processes, via the communication through the
chemical trail, and on dispersion phenomena. These latter
vary as a function of the size of the individuals and of the
task they achieve, but give rise to comparable organisations
in the species studied. The originality of this work lies in
the fact that it shows that the mechanisms of dispersion
allowing the regulation of the traffic and the prevention of
crowding are a by-product of the interattraction processes.
-----------------------------------
Seminar: Wednesday 22 November. 3:30 Afternoon Tea, 4:00pm
seminar
Place: Room 621/622, GP South (Building 78)
Speaker, Jerome Buhl, Postdoctoral Fellow, School of
Biological Sciences, The University of Sydney
Title: From disorder to order in animal collective
motion
Abstract: Despite the huge difference in the scale of animal
aggregations and the cognitive abilities of group members,
the similarities in the patterns they produce have suggested
that general principles may underlie collective motion.
Recent models of "Self-Propelled Particles" have predicted
that mass migrating animal groups may share group-level
properties irrespective of the type of animals in the group.
One key prediction is that as the density of animals in the
group increases, a rapid transition occurs from disordered
movement of individuals within the group to highly aligned
collective motion. Understanding such a transition is
crucial to the prediction and control of mobile swarming
insect pests such as the desert locust in which the
formation of cohesive marching groups of wingless nymphs can
lead to disastrous outbreaks. By studying locust groups in
the laboratory experiments, we were able confirm the
prediction of a rapid transition from disordered to ordered
movement and identify a critical density for the onset of
coordinated marching in locust nymphs. Since SPP models
underlie many theoretical predictions about how groups form
complex patterns, avoid predators, forage, and make
decisions, these results have fundamental implications for
how we understand all aspects of the motion of animal
groups.
Research interests:
Collective behaviour in animal societies with a particular
interest on collective movements, aggregation and
synchronisation; self-organisation; evolution of sociality;
mathematical biology and modelling
