Invasive European wasps alter scavenging dynamics around carrion

Abstract

European wasps (Vespula germanica) have invaded parts of North and South America, Australia and New Zealand. They are opportunistic predators and scavengers that can disrupt food webs and species interactions, but their role in food webs associated with carrion is poorly understood. In this study we examined wasp abundance at 20 vertebrate carcasses in south-eastern Australia. We also collected data on the abundance of blowflies and the occurrence and behavior of vertebrate scavengers at the same carcasses. Wasps arrived within minutes of deploying fresh carcasses and were approximately 4.3 times more abundant in forest compared with grassland habitats. Wasps killed and mutilated native blowflies and may have prevented them from ovipositing on carcasses, as we subsequently found that these carcasses were devoid of fly larvae. European wasps also appeared to interfere with dingoes (Canis dingo) feeding on carcasses, based on observations from cameras showing dingoes snapping their heads in the air and then retreating from the carcasses suddenly. The other major vertebrate scavenger in the system, feral pigs (Sus scrofa), did not show similar behavioral responses. Although we observed European wasps feeding on carcasses, carcass mass loss was slow. This could be a direct result of European wasps suppressing flies and potentially excluding dingoes from accessing carcasses. We conclude that European wasps may alter the way energy flows through scavenging food webs, which could have cascading impacts on ecosystem dynamics and services, although manipulative experiments would help to further evaluate these possibilities.