The impact of feral pigs (Sus scrofa) on an Australian lowland tropical rainforestD. L. Taylor A , L. K.-P. Leung A D and I. J. Gordon B C
A School of Animal Studies, University of Queensland, Gatton, Qld 4343, Australia.
B Sustainable Ecosystems, CSIRO, Davies Laboratory, PMB PO, Aitkenvale, Qld 4814, Australia.
C Present address: The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.
D Corresponding author. Email: email@example.com
Wildlife Research 38(5) 437-445 https://doi.org/10.1071/WR08138
Submitted: 26 September 2009 Accepted: 8 March 2011 Published: 12 October 2011
Context: Feral pigs are thought to damage tropical rainforests, but long-term impact has not yet been quantified.
Aims: This study aimed to determine the impact of feral pigs on soil, soil biota and vegetation in a lowland tropical rainforest in Daintree, north-eastern Australia, and the recovery following exclusion of feral pigs for 12 years.
Methods: Three types of plots were established in 1994: damaged plots were fenced in areas where severe damage had already occurred (‘fenced damaged’); undamaged plots were fenced in areas showing no evidence of damage (‘fenced undamaged’); and unfenced plots were randomly placed and remained at risk of damage (‘unfenced’).
Key results: In 2006, feral pigs had caused significant declines in seedling density, soil macroinvertebrate density and leaf litter cover, but not in soil pH, soil conductivity, invertebrate diversity, vegetation diversity, tree density, canopy cover or fallen log cover. Mean seedling density was lower in the fenced damaged plots than the fenced undamaged plots in 1994 but not in 2006. Other response variables also did not differ significantly between these two plot types, indicating that any damage caused by feral pigs to soil, soil biota or vegetation before 1994 was fully recovered within 12 years.
Conclusions: Our findings suggest that reductions in soil invertebrate density, seedling density, and leaf litter cover should be monitored regularly to inform feral pig management programs, and that these variables should be measured for objective assessment of the outcome of any feral pig control program. These declines may continue and be translated into the decline of trees and other keystone species or processes into the future.
Implications: The efficacy of feral pig control programs can be assessed using the quantitative analysis of the aforementioned variables. The results of such monitoring programs, in conjunction with baseline data, can provide an indication of ecosystem recovery and therefore the level of success achieved by the applied control measures.
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