Drop or fly? Negative genetic correlation between death-feigning intensity and flying ability as alternative anti-predator strategies.

A prey animal may have the alternative of flying away or feigning death when it encounters predators. These alternatives have a genetic base as anti-predator strategies in the adzuki bean beetle, Callosobruchus chinensis. A negative genetic correlation between death-feigning intensity and flying ability was found in C. chinensis, i.e. lower flying ability is genetically connected to escaping by dropping from a perch and then feigning death, whereas higher flying ability does not correspond to death-feigning behaviour. Two bidirectional artificial selections for death-feigning duration and flying ability were conducted independently in C. chinensis. The strains selected for shorter (longer) duration of death-feigning had higher (lower) flying ability, while the strains selected for lower (higher) flying ability showed longer (shorter) duration of death-feigning. When the two traits were compared in 21 populations of C. chinensis derived from different geographical regions, a significant negative correlation was found between death-feigning intensity and flying ability. Based on these results, the choice between alternative escaping behaviours in animals is discussed from two points of view: phenotypic plasticity, an individual with two tactics; and pleiotropic genetic correlation, different individuals with opposite strategies.