I’ve worked on a number of projects investigating the behavioral and ecological mechanisms underlying migratory band formation and movement in the Mormon cricket, Anabrus simplex (Tettigoniidae). Mormon crickets can form huge migratory bands in the western U.S. consisting of millions of individuals that travel en masse up to 2 km/day and can devastate agricultural areas (see photo and video above). Despite the obvious similarities between migratory bands of Mormon crickets and those of locusts, my laboratory work on Mormon cricket behavior demonstrated that the behavioral mechanisms underlying band formation and movement are quite different in the two groups (Sword, 2005).
In collaboration with Pat Lorch (Kent State university), Darryl Gwynne (University of Toronto, Mississauga), and Bob Srygley (USDA-ARS) we used radiotelemetry, GPS, and GIS to examine the landscape-scale movement patterns of individual Mormon crickets within migratory bands. To date, we have tested hypotheses about differences between the movement patterns of individuals in outbreak and non-outbreak populations (Lorch et al. 2005), and also examined the effects of various environmental and social cues on migratory band movement patterns (Sword et al. 2008; Srygley et al. 2009).
We also performed a key manipulative experiment with Mormon crickets demonstrating for the first time that migratory bands function as part of an anti-predator strategy (Sword et al., 2005). However, once these groups form, individuals in the group must contend with increased competition for resources as well as the threat cannibalism. In a really neat set of experiments conducted with Steve Simpson (University of Sydney) and Iain Couzin (Princeton), we demonstrated that Mormon crickets in migratory bands move for two reasons: 1) to exploit new nutritional resources, namely protein and salt, and 2) to avoid being eaten by hungry conspecifics approaching from the rear (Simpson et al. 2006). These findings provided a unique demonstration of the nutritional basis of mass movement and a novel perspective on the mechanisms underlying collective animal movement patterns. In short, Mormon cricket migratory band movement is a forced march driven by cannibalism. Run!!!
Below is a video put together for a story that ran in New Scientist magazine. It features my video of marching crickets above as well as some of the actual data videos used in the Simpson et al. (2006) study to quantify the nutritional state of Mormon crickets while marching in migratory bands.
Cresswell, K.A., Satterthwaite W.H. & Sword, G.A. (2011) Understanding the evolution of migration through empirical examples. In: Fryxell, J., Milner-Gulland, E.J. & Sinclair, A.R.E. (eds.) Migration – A Synthesis. Oxford University Press, Oxford, pp 7-16.
Bazazi, S., Ioannou, C., Simpson, S.J., Sword, G.A., Tourney, C. Lorch, P.D. & Couzin, I.D. (2010) The social context of cannibalism in migratory bands of the Mormon cricket. PLoS ONE 5, e15118.
Srygley, R.B., Lorch, P.D., Simpson, S.J. & Sword, G.A. (2009) Immediate protein dietary effects on movement and the generalized immunocompetence of migrating Mormon crickets Anabrus simplex (Orthoptera: Tettigoniidae). Ecological Entomology 34:633-688.
Sword, G.A. (2008) Gregarious behaviour in insects. In: Capinera, J. (ed.) Encyclopedia of Entomology. Springer, Netherlands, pp. 1733-1740.
Beekman, M., Sword, G.A. & Simpson, S.J. (2008) Biological foundations of swarm intelligence. In: Blum, C. & Merkle, D. (eds.) Swarm Intelligence – Introduction and applications. Springer, Netherlands, pp. 3-41.
Sword, G.A., Lorch, P.D. & Gwynne, D.T. (2008) A radiotelemetric analysis of the effects of prevailing wind direction on Mormon cricket migratory band movement direction. Environmental Entomology 37:889-896.
Simpson, S.J.*, Sword, G.A.*, Lorch, P.D. & Couzin, I.D. (2006) Cannibal crickets on a forced march for protein and salt. Proceedings of the National Academy of Science USA 103:4152-4156. (* equal contributors)
Sword, G.A. (2005) Local population density and the activation of movement in migratory band-forming Mormon crickets. Animal Behaviour 69(2):437-444.
Sword, G.A., Lorch, P.D. & Gwynne, D.T. (2005) Migratory bands give crickets protection. Nature 433:703.
Lorch, P.D., Sword, G.A., Gwynne, D.T. & Anderson, G.L. (2005) Radiotelemetry reveals differences in individual movement patterns between outbreak and non-outbreak Mormon cricket populations. Ecological Entomology 30:548-555.