Two foragers of the invasive wasp Vespula vulgaris on a beech tree in a New Zealand forest.
Credit: Julien Grangier
SYDNEY: An invasive wasp species in New Zealand has been observed picking up native ants that compete for protein-rich food supplies and flying them away from the resource, video footage from a new study reveals.
This interference tactic, employed by the common wasp (Vespula vulgaris), represents a novel behaviour that could help researchers understand the negative impact that introduced species have on native populations.
“We have never seen this before – where a flying competitor carries a non-flying competitor away,” said lead author Julien Grangier, a biologist from Victoria University of Wellington in New Zealand. “This is a behaviour aimed to physically prevent the competitor from accessing the disputed resource.”
Ant toss: an effective interference
While it is well documented that social insects such as ants and wasps use interference behaviours to secure food supplies, researchers say this is one of the first accounts of direct physical interference between members of these two groups.
According to the study published in Biology Letters more than 60 interactions were observed in which individual wasps physically removed the competition, carrying the two millimetre Prolasius advenus ant upwards of eight centimetres before dropping them down, relatively unharmed.
“The human equivalent would be about half the length of a football field,” said Grangier, adding that the behaviour is quite effective. “In about 50% of the cases the ants don’t go back to the food resource, suggesting they are quite disturbed and disoriented.”
Asymmetric advantage favours wasps
Researchers set up 48 bait stations in the beech forests of South Island using tuna to simulate a protein-rich food source such as a dead insect carcass. These stations were then filmed to observe the competitive interactions of wasps and ants.
While wasps tended to avoid confrontation in the majority of the observed situations, they sometimes initiated physical contact, using their asymmetric advantage in terms of size and flight capability to access the food.
The frequency and effectiveness of these interference behaviours were observed to increase when the number of ants at a food site was greater, Grangier said.
