Aggressive Interactions and Feeding Success of Scavenging Grasshoppers (Orthoptera: Acrididae)

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Abstract
Scavenging of arthropod tissue by grasshoppers has been hypothesized to be an important aspect of their diet selection and an important route of pathogen transmission. By placing grasshopper cadavers in the field, we determined that the frequency distributions of nymphs and adults of different species observed scavenging differed from that in the local grasshopper community. Only four of the 10 species present in sweep samples were observed scavenging grasshopper cadavers. The largest species, Melanoplus packardii Scudder tended to be present among scavengers in proportions much greater than its representation in the community. The most abundant species at the two research sites, Melanoplus sanguinipes F. and Aulocara elliotti (Thomas) tended either to be underrepresented in the scavenger samples or to be present in proportions equal to those in the community. Access to the cadavers was strongly related to success in aggressive interactions among grasshoppers congregating at feeding sites. We observed both intra- and interspecific competitive interactions among grasshoppers. Using a logistic regression model that took into account the size differences among contestants and the species involved in each interaction, we found a good match between the observed and expected number of fights won by each species/sex/developmental stage class. M. packardii and M. sanguinipes tended to win fights when they were matched against smaller opponents, but A. elliotti lost more fights than expected from their size alone. Neither sex nor status of the contestants as resident and intruder at a cadaver had a significant effect on the outcome of interactions.

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