Wild pigs aren’t exactly delicate eaters. They root through leaf litter for fruit and bugs, stir up the soil with their snouts and hooves, and generally make a big mess. Now researchers have found that these disorderly habits may have encouraged invasive plants to move into a tropical forest.
The team studied the Pasoh Forest Reserve in Malaysia, where the invasive woody shrub Clidemia hirta has taken root. Scientists suspected that wild pigs might be to blame, since these animals are common in the area. The pigs often spend their nights gobbling fruit in neighboring oil palm plantations, then head to the forest in the daytime to eat more and sleep.
To find out if the pigs were responsible for the shrub invasion, the study authors analyzed three transects in the forest, each 1 kilometer long and 6 meters wide. For each 5-meter section within each transect, the team determined how far the section was from the oil palm plantation border, how many C. hirta shrubs it contained, and how much the soil had been disturbed by pigs.
The closer the section was to the oil palm plantation, the more disturbed the soil, the researchers found. Areas with churned-up dirt also tended to have more invasive shrubs. The results suggest that the oil palm plantations allowed pigs to flourish at the forest-plantation boundary, which then helped the shrubs invade, the authors report in PLoS ONE.
The effects weren’t confined to the forest’s edges: the team saw evidence of pig activity and many shrubs as far as a kilometer away from the border. The wild pigs are “mobile ecosystem engineers,” the team writes, and their digging is probably “having a profound effect on the plant community.” — Roberta Kwok | 22 May 2012
Source: Fujinuma, J. and R.D. Harrison. 2012. Wild pigs (Sus scrofa) mediate large-scale edge effects in a lowland tropical rainforest in Peninsular Malaysia. PLoS ONE doi: 10.1371/journal.pone.0037321.
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