Evol Ecol Res 6: 201-213 (2004)     Full PDF if your library subscribes.

Indirect effects of prey coloration on predation risk: pygmy grasshoppers versus lizards

Emilio Civantos,1* Jonas Ahnesjö,2 Anders Forsman,2 José Martín1 and Pilar López1

1Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales (CSIC), c/ José Gutiérrez Abascal 2, 28006 Madrid, Spain and  2Department of Biology and Environmental Science, Kalmar University, 391 82 Kalmar, Sweden

Author to whom all correspondence should be addressed.
e-mail: e.civantos@mncn.csic.es


Because body temperature influences the physiology, behaviour and performance of ectothermic organisms, thermal conditions might influence the frequency and outcome of predator–prey interactions. Furthermore, differences in colour pattern among prey individuals may indirectly influence predation risk, through effects of coloration on body temperature. We performed staged encounters between lizards (Psammodromus algirus) and grasshoppers (Tetrix subulata). We painted the dorsal surface of grasshoppers either black or grey to manipulate their body temperature and behaviour, and exposed them to predation under two different thermal conditions (sun and shade). Grasshoppers were less active in the presence of a lizard, suggesting that they modified their behaviour to avoid detection. Lizards were more active and attacked the grasshoppers more frequently in the sun than in the shade. However, the proportion of unsuccessful attacks did not differ between sun and shade, suggesting that thermal environment did not influence the relative performance of predators and prey. In the sun, black grasshoppers were more active and tended to be attacked more frequently than grey ones, albeit not significantly so. However, mortality did not differ between black and grey individuals. This suggests that an elevated activity need not translate into increased predation if accompanied by enhanced escape performance. Conversely, individuals may compensate for a poor escape performance associated with low body temperatures by reducing activity. Our findings suggest that selection imposed by predators may favour certain combinations of prey coloration and behaviour, and that colour polymorphism in ectotherms may be influenced also by indirect effects of coloration on predation risk. Counter to intuition, the existence of such indirect effects raises the possibility that the evolution of prey coloration may be governed by selection imposed also by colour-blind or even totally blind predators.

Keywords: activity, coloration, grasshoppers, lizards, predation, prey, temperature.

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