Ecology, Conservation and Management of Wild Pigs and Peccaries

Part III: Conservation and Management

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There are 28 papers concerning the impact of wild boar root-

ing on soil. Wild boar are one of the main natural agents caus-

ing soil disturbance (Bueno et al. 2013), an effect expected by a

powerful ecosystem engineer. This kind of impact, albeit over-

looked in many studies (Mohr et al. 2005), can have cascading

and long-term effects in the ecosystems by varying the fertil-

ity of soil. Changes in soil chemistry may favour some species

of plants and hamper others. For example, a pattern of severe

changes in soil physical–chemical properties was shown in the

Pyrenees by Bueno et al. (2013). It is important to investigate the

consequences of soil bioturbation for nutrient cycling. Aeration

of the soil, incorporation of litter into the soil and mixing of soil

layers increase pH, enhanced microbial activity and thus the

release of nutrients into the soil. As well, rooting can disturb

litter organisms and accelerate nutrient leaching and soil ero-

sion (Mohr et al. 2005). Interestingly, Risch et al. (2010) showed

that rooting increases CO 2 emission in a beech (Fagus sylvatica)

forest. Thus, if the number of wild boar is going to increase fur-

ther, as Massei et al. (2015) suggest, the impact of this species

on CO 2 emission could become non-neglectable. On the other

hand, Moody and Jones (2000) were unable to detect meaning-

ful soil modification determined by the presence of feral pigs

on the island of Santa Cruz. The general pattern is shown in

Figure 36.3: positive impacts are associated with an increase of

soil humidity and increased mineralization rates. Two papers

(Kaller & Kelso 2006; Kaller et  al. 2007) about the impacts of

wild boars on streams of Louisiana report an increase of faecal

coliform bacteria in relation to swine presence and activity. On

average, microbial soil biomass decomposition rates and release

of nitrogen compounds appear not to be influenced as much,

while pH appears to decrease with wild boar activity.

Discussion

It is clear that the validity and generality of the patterns described

above are conditional on the appropriateness of the methods

used to investigate wild boar impacts on ecosystems. This aspect

of the methodological power and reliability of studies on wild

boar has been overlooked by previous reviews, but we believe it

is worth analysing to improve research quality on this subject.

The average study length was very low (29.1 ± 30 months)

and it is significantly longer for introduced than native popu-

lations (Fisher exact test P = 0.025), as shown in Figure 36.4.

In particular, for many native populations the survey lasted for

one year or less, while in the case of introduced populations we

find a modal duration of two years. Finally, Figure 36.5 shows

Figure 36.2 Correspondence

analysis. We report the observed

impact (Effect) of wild boar relative

to the column Biodiv (Appendix

36.1) in relation to the origin of

populations (Origin), Landscape,

Habitat and Climate in a sample

of 29 peer-reviewed publications.

Confidence ellipses refer to null (black

dotted line, 95 per cent), negative

(black continuous line, 95 per cent).

For positive effects no ellipse was

computed because the categories

associated to this effect are < 4.

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