Eradication of an invasive Pallas's squirrel Callosciurus erythraeus population in Flanders (northern Belgium)

Despite a growing catalogue of eradication projects, documented successful
vertebrate eradications on the mainland remain scarce. Reporting on successful
campaigns is crucial to counter pessimism on ambitious programmes to tackle
invasive species and to allow conservation practitioners, wildlife managers and
scientist to learn from previous experience. Moreover, there is a need for basic
information on the effectiveness of control methods and management strategies
that can be used. In this note we report on a successful low-tech eradication
campaign of a local population of Pallas’s squirrel Callosciurus erythraeus, a
species of tree squirrel with documented ecological and socio-economic impacts
in its invasive range. The population was eradicated from a suburban park of
about fifteen hectares using baited mesh wire life traps, in five consecutive
capture campaigns between October 2005 and January 2011. Using maximum
likelihood estimation from catch-effort data we calculated initial densities in
the park at 3 squirrels ha-1. Although control started quickly and the extent of
the invasion was limited, the campaign took over five years and required an
estimated investment of over €200,000 including 1,5 years of post-eradication
surveying. We provide basic data on the methods used to eradicate this invasive
rodent. Critical success factors and possible improvements with respect to the
specific context of this case are discussed. Adding this species to the list of
species of EU concern currently under development could provide incentive to
minimise impact of this tree squirrel at the continental scale.