Initiation and spread of escape waves within animal groups

The exceptional reactivity of animal collectives to predatory attacks is thought to be due to rapid, but local, transfer of information between group members. These groups turn together in unison and produce escape waves. However, it is not clear how escape waves are created from local interactions, nor is it understood how these patterns are shaped by natural selection. By startling schools of fish with a simulated attack in an experimental arena, we demonstrate that changes in the direction and speed by a small percentage of individuals that detect the danger initiate an escape wave. This escape wave consists of a densely packed band of individuals that causes other school members to change direction. In the majority of cases this wave passes through the entire group. We use a simulation model to demonstrate that this mechanism can, through local interactions alone, produce arbitrarily large escape waves. In the model, when we set the group density to that seen in real fish schools, we find that the risk to the members at the edge of the group is roughly equal to the risk of those within the group. Our experiments and modelling results provide a plausible explanation for how escape waves propagate in Nature without centralised control

Ergodic directional switching in mobile insect groups

We obtain a Fokker-Planck equation describing experimental data on the collective motion of locusts. The noise is of internal origin and due to the discrete character and finite number of constituents of the swarm. The stationary probability distribution shows a rich phenomenology including non-monotonic behavior of several order/disorder transition indicators in noise intensity. This complex behavior arises naturally as a result of the randomness in the system. Its counterintuitive character challenges standard interpretations of noise induced transitions and calls for an extension of this theory in order to capture the behavior of certain classes of biologically motivated models. Our results suggest that the collective switches of the group's direction of motion might be due to a random ergodic effect and, as such, they are inherent to group formation.Comment: Physical Review Focus 26, July 201

Onset of collective motion in locusts is captured by a minimal model

We present a minimal model to describe the onset of collective motion seen when a population of locusts are placed in an annular arena. At low densities motion is disordered, while at high densities locusts march in a common direction, which may reverse during the experiment. The data are well captured by an individual-based model, in which demographic noise leads to the observed density-dependent effects. By fitting the model parameters to equation-free coefficients, we give a quantitative comparison, showing time series, stationary distributions, and the mean switching times between states

Diagnóstico general y servicio prestado en la Cooperativa Agrícola Integral Unión de 4 Pinos R.L. Santiago Sacatepéquez, Guatemala C.A. y evaluación de Boscalid + Pyraclostrobin en la producción y prolongación de vida en anaquel del zucchini (Cucúrbita pepo L. subsp. pepo.)

La presente investigación se realizó en a Cooperativa Agrícola Integral Unión de 4 Pinos, R.L., Finca La Suiza, San Lucas Sacatepéquez, mediante el diagnóstico realizado en Finca La Suiza, área productora de Cooperativa Agrícola Integral Unión de 4 Pinos, determinando que la importancia de investigar el uso de nuevas tecnologías que aumenten la vida de anaquel del zucchini. La investigación consistió en la evaluación del efecto de los ingredientes activos Boscalid+Pyraclostrobin en la producción y prolongación de vida en anaquel del zucchini, para lo cual el ensayo fue dividido en dos etapas, la primera la producción en campo y la segunda el manejo postcosecha en planta empacadora. La primera parte fue realizada en Finca La Suiza, para lo cual se elaboró un plan de manejo fitosanitario, tomando como base el plan de manejo fitosanitario para el cultivo de zucchini Departamento Agrícola 2009, a la cual se incluyeron las aplicaciones de la estrobilurina (Boscalid+Pyraclostrobin) se evaluaron cuatro tratamientos, de los cuales uno era el testigo absoluto, dos tratamientos con 2 y 3 aplicaciones de la estrobilurina (Boscalid+Pyraclostrobin) en diferentes etapas fenológicas del cultivo y un cuarto tratamiento el manejo tradicional del Departamento Agrícola, asi como manejo postcosecha del producto, el cual fue sometido a un procedimiento de clasificación, lavado, desinfección, empaque y colocación en cuarto frio (4ºC) para determinar los días de vida en anaquel del zucchini

A numerical scheme for non-local aggregation with non-linear diffusion and approximations of social potential

Aggregations abound in nature, from cell formations to locust swarms. One method of modelling these aggregations is the non-local aggregation equation with the addition of degenerate diffusion. In this article we develop a finite volume based numerical scheme for this style of equation and perform an error, computation time, and convergence analysis. In addition we investigate two methods for approximating the non-local component. References A. J. Bernoff and C. M. Topaz. Nonlocal aggregation models: A primer of swarm equilibria. SIAM Rev. 55.4 (2013), pp. 709–747. doi: 10.1137/130925669 R. Bürger, D. Inzunza, P. Mulet, and L. M. Villada. Implicit-explicit methods for a class of nonlinear nonlocal gradient flow equations modelling collective behaviour. Appl. Numer. Math. 144 (2019), pp. 234–252. doi: 10.1016/j.apnum.2019.04.018 J. A. Carrillo, A. Chertock, and Y. Huang. A finite-volume method for nonlinear nonlocal equations with a gradient flow structure. In: Commun. Comput. Phys. 17.1 (2015), pp. 233–258. doi: 10.4208/cicp.160214.010814a J. R. Dormand and P. J. Prince. A family of embedded Runge–Kutta formulae. J. Comput. Appl. Math. 6.1 (1980), pp. 19–26. doi: 10.1016/0771-050X(80)90013-3 J. von zur Gathen and J. Gerhard. Modern computer algebra. 3rd ed. Cambridge University Press, 2013. doi: 10.1017/CBO9781139856065 F. Georgiou, J. Buhl, J. E. F. Green, B. Lamichhane, and N. Thamwattana. Modelling locust foraging: How and why food affects group formation. PLOS Comput. Biol. 17.7 (2021), e1008353. doi: 10.1371/journal.pcbi.1008353 F. Georgiou, B. P. Lamichhane, and N. Thamwattana. An adaptive numerical scheme for a partial integro-differential equation. Proceedings of the 18th Biennial Computational Techniques and Applications Conference, CTAC-2018. Ed. by B. Lamichhane, T. Tran, and J. Bunder. Vol. 60. ANZIAM J. 2019, pp. C187–C200. doi: 10.21914/anziamj.v60i0.14066 F. Georgiou, N. Thamwattana, and B. P. Lamichhane. Modelling cell aggregation using a modified swarm model. Proceedings of the 23rd International Congress on Modelling and Simulation, MODSIM2019. Vol. 6. 2019, pp. 22–27. doi: 10.36334/modsim.2019.a1.georgiou J. E. F. Green, S. L. Waters, J. P. Whiteley, L. Edelstein-Keshet, K. M. Shakesheff, and H. M. Byrne. Non-local models for the formation of hepatocyte–stellate cell aggregates. J. Theor. Bio. 267.1 (2010), pp. 106–120. doi: 10.1016/j.jtbi.2010.08.013 R. J. LeVeque. Finite-volume methods for hyperbolic Pproblems. Cambridge Texts in Applied Mathematics. Cambridge University Press, 2002. doi: 10.1017/CBO9780511791253 C. F. Van Loan. Introduction to Scientific Computing: A Matrix Vector Approach Using MATLAB. 1997. url: https://www.pearson.com/us/higher-education/program/Van- Loan-Introduction-to-Scientific-Computing-A-Matrix-Vector- Approach-Using-MATLAB-2nd-Edition/PGM215520.html A. Mogilner and L. Edelstein-Keshet. A non-local model for a swarm. J. Math. Bio. 38.6 (1999), pp. 534–570. doi: 10.1007/s002850050158 C. M. Topaz, A. L. Bertozzi, and M. A. Lewis. A nonlocal continuum model for biological aggregation. Bull. Math. Biol. 68 (2006), p. 1601. doi: 10.1007/s11538-006-9088-6 C. M. Topaz, M. R. D’Orsogna, L. Edelstein-Keshet, and A. J. Bernoff. Locust dynamics: Behavioral phase change and swarming. PLOS Comput. Bio. 8.8 (2012), e1002642. doi: 10.1371/journal.pcbi.100264

Information transfer in moving animal groups

Moving animal groups provide some of the most intriguing and difficult to characterise examples of collective behaviour. We review some recent (and not so recent) empirical research on the motion of animal groups, including fish, locusts and homing pigeons. An important concept which unifies our understanding of these groups is that of transfer of directional information. Individuals which change their direction of travel in response to the direction taken by their near neighbours can quickly transfer information about the presence of a predatory threat or food source. We show that such information transfer is optimised when the density of individuals in a group is close to that at which a phase transition occurs between random and ordered motion. Similarly, we show that even relatively small differences in information possessed by group members can lead to strong collective-level decisions for one of two options. By combining the use of self-propelled particle and social force models of collective motion with thinking about the evolution of flocking we aim to better understand how complexity arises within these groups.publishe

Regulation of macronutrient intake in termites: A dietary self-selection experiment

International audienceMany animals have been shown to select among nutritionally complementary foods to reach a specific balance of nutrients that optimizes key life history traits. Nutritional ecology theory, however, predicts that an animal with a diet that is very stable in its composition, and with nutritional requirements that do not vary in their balance through time, would not need to display such mechanisms of regulation. Here we use the Australian termite Nasutitermes exitiosus as a model to test this prediction for the first time. We used the nutritional geometric framework to investigate the regulation of carbohydrate and protein, as well as the effects on foraging behaviour of protein type and group caste composition and size. Our results support the prediction of nutritional ecology, as termites failed to actively defend a well-defined macronutrient ratio. Termites maintained food collection relatively constant across protein type and group composition, and only appear to vary their collection by avoiding diets too rich in protein

Tunnelling

Tunnelling activity for each nest, measured every 6 days