Implications for the management of the exotic Vespa velutina
The European Union listed Asian-hornets as an invasive alien species of
concern in 2014 (UE1143/2014). Our results agree with Rebollo et
al . (2023) regarding the predation pressure of honey-buzzards on this
species, which could be of interest for the management of the exotic
wasp, at least on a small scale in the proximity of honey-buzzards´
nests. Four years after colonization, the Asian hornet became the second
most important prey of honey-buzzards in the study area. Our findings
allow us to identify two aspects of the Asian-hornet honey-buzzard
interaction that could limit the magnitude of honey-buzzards´ effects on
the exotic wasp. On one hand, honey-buzzards did not appear to show a
preference for Asian-hornets compared to the native common-wasps,likely because the annual life cycle of Asian-hornet colonies is not
entirely underground, and this predator has specific adaptations to
primarily target upon underground nests. It would be expected that in
those years in which the phenology of Asian-hornets is delayed due to
weather conditions, honey-buzzards would include a higher proportion of
the exotic wasp in their diet. On the other hand, the degree of
specialization exhibited by honey-buzzards on common-wasps may make them
particularly vulnerable to invasion by Asian-hornets. Since its arrival,
Asian-hornets have become the most abundant social wasps in the study
area, and their presence may have a direct impact on the populations of
common-wasps, both through direct predation and competition for
resources. We observed Asian-hornets preying on common-wasp workers at
the entrance of their nest, especially after a honey-buzzard attack on
common-wasp colony, which could have a demographic effect on
common-wasps. If the exotic hornet manages to significantly reduce the
populations of common-wasps, honey-buzzard´s populations could decrease
unless they adapt their trophic preferences and hunting behaviour to
compensate for the decrease in its staple prey. There are examples where
an invasive species affects the staple prey of a raptor, leading to its
local extinction (Spencer et al . 1991). Future long-term research
should study the evolution of honey-buzzards´ preferences for
Asian-hornets. Additionally, the effects of this species on
ecosystem services provided by European native wasps and on the density
of predators specialized in the consumption of native wasps, such as
honey-buzzards, should be considered.