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| The introduction of alien species to new environments is one of the main threats
to the conservation of biodiversity. One particularly problematic example is that of
wild ungulates which are increasingly being established in regions outside their
natural distribution range due to human hunting interests. Unfortunately, we know
little of the effects these large herbivores may have on the host ecosystems. This study
deals with a first comparative analysis of the habitat requirements of two ungulate
species that may be facing competition for resources in the south of Europe: the
native Iberian ibex (
Capra pyrenaica
) and the exotic aoudad (
Ammotragus lervia
).
The aoudad is a North African caprid introduced in 1970 as a game species in southeastern
Spain. It has adapted well, and populations have been freely expanding since
then. Ecological Niche Factor Analysis is used to describe the realized niche of both
species where their distribution ranges merge. Both species occupy marginal areas of
rugged terrain in the region. Marginality is higher for the Iberian ibex, which also
presents a higher tolerance of secondary environmental gradients than the aoudad.
Highly suitable areas for each species are secondarily suitable for the other. Reclassified
and cross-tabulated habitat suitability maps showing the areas of potential spatial
coexistence and differences in ecological traits between both species are provided.
The results obtained do not allow inferring resource competition between these
species. However, current aoudad expansion could result in it invading the favoured
habitats of the ibex. Inadequate hunting policy and monitoring, and increasing
climatic resemblance of the study region to the native aoudad areas, due to a strong
desertification process, are facilitating a high rate of expansion. We strongly recommend
to eradicate or, at least, monitor these exotic populations, and promote active
conservation practices, if one wants to preserve the unique natural resources present
in this European region. | |
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