Biology subjects

Fourcassie, V.

Publications and source records attributed to Fourcassie, V..

4 recordsLinked to original sources

bioRxiv2025

Discovering search behaviour in black garden ant trajectories

Exploration of space plays an important role in many animals, in particular for social insects who have to feed and protect a whole colony. In a laboratory study, Khuong et al (2013) studied how the workers of the black garden ant Lasius niger move around in an unknown environment. They assumed that, in a homogeneous arena with no visual cues, ants had no information about their position in space. Based on this hypothesis, they modelled their ants in a Boltzmann Walker framework which describes an ants random walk as a series of straight segments separated by reorientation events. They assumed that on plain horizontal surfaces the ants direction of movement would not influence their average speed, segment lengths and reorientation decisions, thus leading to diffusive trajectories. However, published experiments indicate that L. niger ants are not completely devoid of directional information even in standard laboratory setups with no obvious landmarks. Moreover, many ant species are known to develop specific search strategies when they want to find a particular place in space, a situation that may apply to the analysed data. We re-analyze Khuong et al s data on non-inclined surfaces, this time taking into account the ants orientation in relation to its starting point in the arena. We discovered that, with this information taken into account, the ants trajectory is biased towards its starting point (biased random walk), revealing an advecto-diffusive process. In fact, the distributions of segment lengths and reorientation angles turned out to be modulated by the ants orientation in relation to its starting point. By simulating these biased trajectories, we show that this modulation halves the time it takes for an ant to come back towards its starting point. We conclude that not taking into account the animals cognitive abilities in data analysis may lead to incomplete or biased conclusions. The discovered search behaviour in L. niger can play a significant role in the colonys exploration and foraging ecology.

animal behavior and cognition↗

bioRxiv2021

Biomechanical effects of the addition of a precision constraint on a collective load carriage task

1Team lifting is a complex and collective motor task that possesses both motor and cognitive components. The purpose of this study was to investigate to what extent the biomechanics of a collective load carriage is affected when a dyad of individuals is performing a carrying task with an additional accuracy constraint. Ten dyads performed a first condition in which they collectively transported a load (CC), and a second one in which they transported the same load while maintaining a ball in a target position on its top (PC). The recovery-rate, amplitude, and period of the center-of-mass (COM) trajectory were computed for the whole system (dyad + table = PACS). We analyzed the forces and moments exerted at each joint of the upper limbs of the subjects. We observed a decrease in the overall performance of the dyads when the Precision task was added, i.e., i) the velocity and amplitude of CoMPACS decreased by 1,7% and 5,8%, respectively, ii) inter-subject variability of the Moment-Cost-Function decreased by 95% and recovery rate decreased by 19,2% during PC. A kinetic synergy analysis showed that the subjects reorganized their coordination in the PC. Our results demonstrate that adding a precision task affects the economy of collective load carriage. Notwithstanding, the joint moments at the upper-limbs are better balanced and co-vary more across the paired subjects during the precision task. Our study results may find applications in domains such as Ergonomics, Robotics-developments, and Rehabilitation.

bioengineering↗

bioRxiv2019

Walking kinematics in the polymorphic seed harvester ant Messor barbarus: influence of ant size and load carriage

Ants are famous in the animal kingdom for their amazing load carriage performances. Yet, the mechanisms that allow these insects to maintain their stability when carrying heavy loads have been poorly investigated. Here we present a study of the kinematics of loaded locomotion in the polymorphic seed-harvesting ant Messor barbarus. In this species big ants have larger heads relative to their size than small ants. Hence, their center of mass is shifted forward, and the more so when they are carrying a load in their mandibles. We tested the hypothesis that this could lead to big ants being less statically stable than small ants, thus explaining their lower load carriage performances. When walking unloaded we found that big ants were indeed less statically stable than small ants but that they were nonetheless able to adjust their stepping pattern to partly compensate for this instability. When ants were walking loaded on the other hand, there was no evidence of different locomotor behaviors in individuals of different sizes. Loaded ants, whatever their size, move too slowly to maintain their balance through dynamic stability. Rather, they seem to do so by clinging to the ground with their hind legs during part of a stride. We show through a straightforward model that allometric relationships have a minor role in explaining the differences in load carriage performances between big ants and small ants and that a simple scale effect is sufficient to explain these differences.

animal behavior and cognition↗

bioRxiv2017

Investigating termite nest thermodynamics using a quick-look method and the heat equation

Termite mounds are often cited as an example of efficient thermoregulated structures. Nest thermal stability can be critical for insects that are particularly sensitive to heat and desiccation. Few studies have measured internal temperature of termite nests with respect to environmental parameters, especially in Neotropical species. In this study, we analyzed the thermal profiles of different parts of Procornitermes araujoi nests, a neotropical mound-building termite of the Brazilian cerrado. To read into our dataset we first used rasterization, a method that allows a quick-look assessment of time-series. Our results show that nest architecture efficiently buffers against environmental temperature fluctuations while at the same time maintaining a relatively high internal temperature in the core. This rather stable internal climate follows nevertheless the external temperature long-term averages. Using a novel numerical scheme, we further show that the heat transfer dynamics are well described by the classical heat equation, with an additional heat source whose origin is discussed.

ecology↗