Invasive species have the capacity to cause catastrophic impacts on wildlife.In the US, the recent discovery of the now infamous ‘murder hornets’ have beencausing havoc among bee populations.
In Australia, a new study on invasive European wasps ( Vespula germanica )shows our country is occupied by an insect that swarms decaying corpses,decapitates its prey and picks fights with dingoes.
The study led by Emma Spencer, a PhD student in the Global Ecology Lab in theSchool of Life and Environmental Sciences, looked at European wasps and theirrole as a scavenger.
“These wasps are absolutely ruthless,” Ms Spencer said. “When they see acarcass, it becomes a feeding frenzy for a colony and the wasps will stop atnothing to defend their food.”
During the study, the researchers monitored 20 kangaroo carcasses located in amix of grassland and forest habitats in Kosciuszko National Park. Waspscongregated in large numbers around every carcass. They attacked any blowfliesthat attempted to approach. This wasn’t just evident in the data collected –the researchers sat next to carcasses and saw fly after fly taken to theground by wasps.
Many of these flies showed signs of mutilation.
“To our surprise, some were even missing their heads,” Ms Spencer said. “In aneffort to protect ‘their’ carcass, the European wasps were decapitating flies.This may have simply been defensive behaviour, but they could have also beentaking bits of flies back to their nest for larvae to feed on.”
“We also found that the wasps were bothering animals much larger in size,” MsSpencer said. “Our camera trap images showed dingoes snapping at wasps. Manyof these animals retreated without feeding on the carcasses, presumablybecause the wasps were stinging them.”
This study is just the start of investigations into European wasp impacts inKosciuszko National Park. But it has raised important points on the fate ofcarcasses dominated by wasps. For one, it seems that blowflies and dingoes aresometimes prevented from doing their job of ‘cleaning up’ carcasses in thelandscape. Flies are also major pollinators and decapitation isn’t much goodfor pollen transfer.
If wasp numbers are supported by prevalent carcass resources (such as largenumbers being available to them via culling) it may suggest the need toundertake culls of pest species when wasps are not active, such as during thecoldest times of the year.
How do wasps compare to murder hornets?
Like the European wasp, the murder hornet also threatens insect pollinators.The hornets raised alarms in the USA, as they are known to decimatepopulations of honeybees.
Alarms were also raised because people fear the nasty sting associated withthe hornet. In Australia there is also a focus on the impacts of Europeanwasps on human health. But as in the USA, this focus is largely misguided.
“While both insects have painful stings that can result in severe allergicreactions, fatalities are rare,” Ms Spencer said. “We would do well toredirect our concern towards the impacts that they are having on ourecosystems.”
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