Abstract
Across taxa, evolutionary tradeoffs between fecundity and locomotory performance exist. Previous studies have suggested that the maximum jumping ability of gravid grasshoppers is reduced by their egg masses. In gravid American locusts (Schistocera americana), the egg mass is approximately twenty percent of the animals' body mass. To address the cost of added mass during jumping, weights equal to 20% of body mass were attached to female grasshoppers (n=8). The mean maximum jumping distances for the unweighted control group (100±7 cm) and 20% weighted group (105±10 cm) were not significantly different. To determine if males could also compensate for increased weight during jumping, weights equal to 20%, 40%, or 80% of body mass were attached to male grasshoppers (n=8). Maximum jump distance showed an inverse relationship with additional weight in male grasshoppers: unweighted control males jumped 123±9cm, 20% weight males jumped 97.0±4.9 cm, 40% weight males jumped 85.5±10.4 cm, and 80% weight males jumped 83.6±7.3 cm. Gravid females may be capable of compensating for their relatively larger mass by increasing jump energy production. For example, high‐speed video analysis of maximum jump performance showed that gravid females produced greater take‐off velocities (2.88±0.09 m/s) and accelerations (237±18 m/s2) during jumping than non‐gravid females (2.46±0.21 m/s) and (214±22 m/s2), respectively. Future experiments will involve attaching greater amounts of weights to females and analyzing high‐speed video to determine possible mechanisms gravid grasshoppers utilize to mitigate the effects of increased mass on jumping performance.
Published Version
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