Part III: Conservation and Management410
Wirthner et al. (2012) reported an immediate impact of wild
boar rooting on understorey forest composition in Switzerland,
but found that the same plot after 48 months showed no signifi-
cant change in terms of composition and sapling height.
Our plea is for wildlife and environmental agencies to
develop long-term programmes on the ecological impact of the
species in representative ecosystems of both native and invasive
ranges. Unfortunately, most studies were funded by local organ-
izations with limited research aims and were not published in
first-class scientific journals. Further, much evidence is reported
in ‘grey literature’ and was omitted in this review.
Most of studies measured ‘rooting’. This is very easy to
perform, but because the animals root in the same location
several times, a simple evaluation of rooting gives a biased
estimate of the intensity of the animal’s impact in a given
location. Most of the studies that employ fenced plots com-
pare absence to presence without quantifying the abundance
of the species in unfenced plots. This is an important draw-
back whether the relationship between wild boar density and
impact is NOT linear.
Theoretically (Belsky 1897), we expect that intermediate
levels of grazing and rooting by wild boar may improve plantproductivity and biodiversity, but in the absence of density esti-
mates is not possible to identify target densities at which ecosys-
tem services are maximized.
Unfortunately, in the analysed studies there is a lack of any
estimate of wild boar density or abundance. The absence of den-
sity estimates hampers the evaluation of the ecological impact of
wild boar. Indeed, it is quite different for the application of miti-
gation measures if a given impact level is attained at densities of
2 or 20 individuals/km^2. This is particularly relevant for taking
management decisions in parks, and private and public game
reserves.
To estimate wild boar density is not impossible, but requires
monitoring at a local scale. To get reliable estimates of wild boar
abundance and density, at different scales and with acceptable
degrees of accuracy and precision, several methods have been
introduced and field-tested, such as relative presence indices
(Engeman et al. 2013), pellet group counts (Plhal et al. 2014),
mark–resight (Focardi et al. 2008; Franzetti et al. 2012), distance
sampling with thermal imaging (Focardi et al. 2000; Franzetti
et al. 2012), and non-invasive genetics (Ebert et al. 2012).
Recently, some attempts to estimate population were performed
by means of camera trapping (Plhal et al. 2011).Figure 36.4 Histogram of the
duration of the studies (months) for
introduced and native populations..03813:02:26