Chapter 31: Wild boar management in Europe341
Effort to Decrease the Population Numbers
Harvest Planning
Two main conditions have to be fulfilled when managing the
populations. First, the desirable population density has to be
achieved. Second, this should be done by maintaining a popula-
tion structure that is close to the populations that are not hunted
(e.g. Milner et al. 2007).
In order to theoretically plan the number of harvested wild
boar, information about the number of animals in the popula-
tion and the recruitment is required. However, it is well known
that direct-count methods of ungulates in forest habitats at large
spatial scales are costly (Lancia 1994), difficult, and potentially
inaccurate (e.g. Mayle et al. 1999). Estimating wild boar popula-
tion numbers is made more difficult because of their clumped
distribution, complex social structure, nocturnal activity pat-
tern, and preference for dense vegetation. Hence, making
decisions about altering or maintaining the density of the popu-
lation requires feedback information about all of the decisive
constraints deriving from overpopulation. Such decisions can
be supported by time-series indices of hunting bags provided
that they have been previously corrected for hunting effort and
have passed validation (Acevedo et al. 2006).
That an increase in hunting pressure should lead to a decrease
in the population growth rate is obvious. This statement can be
sustained even if we know that the population is able to adapt
to high hunting pressure. The greatly reduced chances of sur-
vival creates selective pressure that favours younger age groups
(Gamelon et al. 2011) and a decreased threshold body mass at
primiparity (Servanty et al. 2009).
It seems that juvenile female survival is one of the most
important if not the decisive influential factor increasing the
population growth rate of the species (Gamelon et al. 2011).
Accordingly, many investigations have shown that the most
effective way to decrease density is to increase the hunt-
ing of piglets and reproductive females (Genov et al. 1994;
Bieber & Ruf 2005; Toïgo et al. 2010). Keuling et al. (2013), for
example, argue for an 80 per cent hunting rate for piglets and an
increased harvest rate for adult females. The intensive harvest-
ing of juveniles is also recommended by Bieber and Ruf (2005)
emphasizing the reduction of this cohort to approximately
15 per cent, including natural mortality. They show that in
good habitat conditions with rich mast production the pref-
erential hunting of adults would be an ineffective method for
stopping population growth. The only case when the reduction
of adult survival is effective is in poor habitat conditions when
the aim is to reduce or even to remove the population from a
specific area.
Although information on the high natural mortality affect-
ing the density of juveniles even in hunted populations does
exist (Náhlik & Sándor 2003), estimating the evaluation of the
juvenile survival/density on a large scale is problematic for the
following reasons: (i) the matrilineal groups begin to disinte-
grate 8–9 months after birth (Spitz 1992); (ii) survival is much
dependent on the severity of the winter (Jędrzejewski et al. 1992);
(iii) juvenile dispersal can vary from year to year as a function
of the density and food supply (Stubbe et al. 1989; Truvé 2004);
(iv) being a polytocous species with high energy expenditure
per breeding, preweaning survival could be sensitive to popula-
tion density (Gaillard et al. 1997).
Apparently, high hunting pressure results in low mean
age, although this also depends on the hunting method used
(Fernández-Llario & Mateos-Quesada 2003). Hunting regu-
lations can also influence the evaluation of the mean age. For
example, if a limitation for the harvesting of females is in effect,
then adult males are burdened with the highest hunting pres-
sure (Gamelon et al. 2011), which reduces the mean age. Or,
if hunting pressure on juveniles is kept too low, as observed
in most central European countries (Keuling et al. 2013), the
decrease of the mean age will continue. To decrease the effect of
the selection for earlier reproduction at primiparity, it is desir-
able to increase the mean age of the population by increasing the
hunting pressure on juveniles.1,8Annual growth rate 5-year growth rate1,61,41,210,8Mean (SE) growth rate0,6
1982 1987 1992 1997 2002 2007 2012Figure 31.3 Mean (SE) estimated
growth rate of wild boar populations
in Europe, derived from hunting bag
statistics calculated for each country
and averaged across 18 countries.
Annual growth rate = number of wild
boar harvested per year divided by
the number of animals harvested the
previous year. Five-year growth rate =
mean number of wild boar harvested
in five years divided by the number of
animals harvested the previous five
years (from Massei et al. 2015). (A black
and white version of this figure will appear
in some formats. For the colour version,
please refer to the plate section.).03312:55:50