Wild boars (Sus scrofa) are native to Europe, Asia and North Africa. They have been introduced to both North and South America and to Oceania, where they are classified as an invasive species. And they can cause major damage to delicate ecosystems.
Their digging habits and omnivorous diets, in addition to their large size and high reproductive rates, make them formidable competitors to native wildlife. And they frequently disrupt the growth of native plant life as they forage.
A recent study published in PeerJ Life and Environment finds that these voracious pigs now pose a threat to monkey puzzle forests in Chile.
Monkey puzzle forests: a unique ecosystem
Monkey puzzle trees (Araucaria araucana) are native to slopes of the Andes Mountains in Chile and Argentina.
Early relatives of these conifers have been found in the fossil record as early as the Late Triassic period. The species has been referred to as a 'living fossil' — a controversial designation that suggests the persistence of ancient lineages in modern times.
Because of their relatively restricted range and threats such as logging, monkey puzzle trees were declared an endangered species by the International Union for the Conservation of Nature (IUCN) in 2013.
“It is a unique ecosystem – endangered and of cultural value,” says co-author Oliver Keuling, senior researcher at the Institute for Aquatic and Terrestrial Wildlife Research, University of Veterinary Medicine in Hannover, Germany.
Into the forest
The researchers set out to determine the prevalence of wild boars in the Villarrica National Park in the Araucanía Region of Chile, which is covered by rare monkey puzzle forests. These forests are interspersed with enga beech trees (Nothofagus pumilio). The understories are largely grasses and bamboo.
Using camera traps, the study authors ascertained that the density of wild boars was approximately 1.4 individuals per square kilometre.
“This allowed us to use a non-invasive way to work out the wild boar density in the area,” Keuling says of the camera trap method.
Wild boar impacts
This is the first ever density estimate for invasive wild boars in South American temperate forests. Densities in their native range may be much higher but given the sensitive nature of the monkey puzzle ecosystem, even small numbers of pigs may cause damage.
They are likely to compete with the birds and rodents that rely on monkey puzzle seeds, which are primary sources of food in an area otherwise poor in resources. The impacts on species such as the Chilean rock rat (Aconaemys fuscus), which relies on monkey puzzle seeds, are unknown.
“Wild boars feed on the seeds, impacting on the regeneration of this forest in a way that we do not yet fully understand,” Keuling says. “Since the forest offers limited alternative food resources, boars likely rely heavily on these seeds.”
Their disruption of seedlings, which take up to 40 years to reach reproductive age, may also have serious impacts on the forest. There are few controls on the wild boars – while pumas (Puma concolor) feed on them, human interventions such as trapping are in early stages.
The authors suggest that further monitoring is necessary to ascertain the long term effects of their activity.
Find out more about the study: First wild boar density data from Araucaria forest in Patagonian Andes
Main image: Wild boars in Villarrica National Park, Chile/Oscar Skewes et al.
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