Impaired escape flight ability in butterflies due to low flight muscle ratio prior to hibernation

Abstract

SUMMARYFor an animal to escape an attacking predator, speed and manoeuvrability are likely to be crucial factors. Previous studies on reptiles and birds have revealed that gaining weight, due to for instance egg load or lipid accumulation, leads to impaired escape ability and possibly increases the risk of being caught by predators. Here we tested whether the flight performance of an insect, the small tortoiseshell butterfly (Aglais urticae), is affected by variations in body mass due to feeding by comparing flight performance parameters between individuals that (i) took flight spontaneously or after being subjected to a simulated predator attack and (ii) varied in flight muscle ratio (FMR: thorax mass/total body mass). The results show that butterflies that were subjected to a simulated predator attack flew at higher velocities and straighter than butterflies that were allowed to take off spontaneously. Furthermore, our study suggests, for the first time, that butterflies may experience impaired escape ability after feeding, which directly leads to a decrease in FMR; a reduction from 0.5 to 0.3 reduced escape flight velocity by about 37% at 0.5·m from the start. Finally, this study shows that FMR affects take-off angle and sinuosity, with steeper angles and more turning in butterflies with low FMR.

Weight Loading and Reproductive Status Affect the Flight Performance of Pieris napi Butterflies

“…Decreased flight activity after mating in male boll-weevils has been suggested to reflect lower motivation to search for females compared to unmated males (Rankin et al 1994). Although the attack by a model predator in this study should encourage males to perform closer to maximum regardless of mating status (Almbro and Kullberg 2008) it cannot be ruled out that also butterflies adjust flight activity when mating has recently taken place. Females tested after oviposition were significantly older than the females in the other two groups, but an average age of 6.7 days did not negatively affect their flight ability, a result consistent with observations by Åhman and Karlsson (2009).…”

“…Room temperature was held at 21±1°C. Because butterflies are known to perform closer to their maximum capacity when under simulated attack (Almbro and Kullberg 2008), a 10 cm rubber lizard on a stick was used as a model predator and manually pushed towards the butterfly to induce flight. Butterflies were allowed a minimum of 3, and a maximum of 5 min, to warm up before an attack was simulated.…”

“…For every individual, velocity and take-off angle were determined using the coordinates provided by the Trackit 3D camera system and Track 3d (software analysing space-time data; Ulf Norberg, Stockholm University). Flight parameters were calculated (as described in Almbro and Kullberg 2008) at 0.1; 0.2; 0.3; 0.4 and 0.5 m distance from the take-off point.…”

Linking biomechanics and ecology through predator–prey interactions: flight performance of dragonflies and their prey

“…Several studies have quantified the escape performance of flying insects but this behavior is usually motivated by artificial or atypical stimuli (e.g. Yager and May, 1990;Srygley and Kingsolver, 2000;Almbro and Kullberg, 2008;Jantzen and Eisner, 2008;Combes et al, 2010), or rarely by a trained predator in pursuit (Srygley and Dudley, 1993). The flight performance of a predator and prey each flying alone under laboratory conditions has been compared (McLachlan et al, 2003), and the flight paths of predators and their prey have been reconstructed to assess interception strategy (Olberg et al, 2000;Ghose et al, 2006;Ghose et al, 2009) but studies of the simultaneous flight mechanics of both participants during natural predatory encounters are virtually non-existent.…”

Energetics of Insect Diapause

“…3. At the molecular level, the regulatory pathways used by insects for accumulating reserves and for regulating the utilization of those reserves as diapause progresses remain largely unknown.…”