Feral pigs

Impacts to ecological values of wetlands from feral pigs

A small group (or even a single feral pig) can cause significant damage to wetland margins in a very short space of time. Because vegetation plays a critical role in stabilising the land, vegetation destruction by feral pigs can lead to higher rates of erosion and nutrient and sediment resuspension into the water column[18].

Feral pigs have potentially been impacting Queensland wetlands for hundreds of years, particularly in North Queensland[5]. Impacts from feral pigs to the ecological values of wetlands can include:

• habitat alteration and degradation from feeding, trampling, pugging, and wallowing activities[17]
• decreased water quality, including decreased water clarity (e.g., increased turbidity), reduced dissolved oxygen levels, and increased nutrient concentrations (e.g., increased ammonium levels)[18]
• decreased aquatic flora cover[1]
• altered structure of plant communities[1][17], leading to increased erosion from vegetation lost and/or structural damage[4]
• altered structure of soil microbial communities[8]
• spread of introduced weeds and pathogens, leading to the loss of sensitive species[1]
• predation on and competition with native wetland animals (e.g., lizards, amphibians, birds, turtles)[1].

Impacts to native wetland animals from feral pigs

Feral pigs prey on native animals found in freshwater (e.g. freshwater crayfish, freshwater turtles) and coastal marine ecosystems (e.g. marine turtle eggs)[1][12]. For example, over 150 freshwater frogs were found in the stomach of a feral pig in Cape York[10][1]. Feral pigs also are a major predator of freshwater northern longneck turtles in Northern Australia[1] and were found to have direct impacts on the habitat of the rare Jardine River Turtle and the turtle itself[6]. On coastal nesting beaches in Northern Australia, feral pigs consume large amounts of marine turtle eggs, contributing to total egg loss in some instances[12].

In some instances, the presence of feral pigs can have negative and positive effects on native Australian fauna[11]. In tropical Australian rainforests, feral pig presence has been shown to drive out native birds, likely due to behavioural avoidance by the birds and competition for resources from feral pigs[11]. However, native birds immediately returned to forage on the resources uncovered through feral pig rooting, likely benefiting from increased resource availability before moving on again[11].

Impacts to water quality from feral pigs

One of the major impacts from feral pig activities in wetlands is on water quality in wetlands. Impacts on water quality from feral pigs can vary across sites due to differing factors but determining specific impacts from pig activities can be difficult. For instance, in unfenced ephemeral floodplain lagoon systems in Northern Queensland, feral pigs destroyed aquatic macrophyte communities and disturbed sediments, significantly affecting water clarity and causing aquatic anaerobic and acidic conditions[5]. Water turbidity caused by pig rooting activities can lower the amount of dissolved oxygen available within the wetland water[10].

Water quality impacts from feral pigs can affect other wetland species that are reliant on the wetland for survival. For example, decreased dissolved oxygen concentrations in pig-impacted wetlands could lead to higher asphyxia exposure risks to freshwater fish, as identified in the Archer River Catchment in North Queensland, due to shallow and disturbed waters, than in deeper, permanent, and pig-managed wetlands[19].

Urination and defecation from feral pigs into waterholes and dams can lead to poor water quality, eutrophication, and parasite/disease presence in the water[7][3][4], limiting safe access to surface water for drinking, cultural, and spiritual use by First Nations people[16].

Impacts to social values of wetlands from feral pigs

In addition to the ecological values impacted by feral pig activities in wetlands, feral pigs can also impact the social values held by the beneficiaries of a wetland. For example, soil disturbance by feral pigs can cause crop damage and transmit diseases to livestock and native wildlife living in wetlands, impacting the services a wetland provides that generate the economic, food security, and biodiversity conservation values enjoyed by beneficiaries[3][13]. Additionally, feral pigs destroy bush tucker harvest sites, drive out culturally important species, and can destroy culturally important sites[2][14][15].

It is important to note that not all beneficiaries of a wetland view the presence of feral pigs as a negative. Feral pigs are considered an important food, employment, and recreational resource to some Aboriginal Australians from Northern Queensland[9][15]. Recreational hunters also view feral pigs as a valuable game species, generating both social and economic values for these beneficiaries[2]. A whole-of-system, values-based management approach can be used to ensure that the differing viewpoints of beneficiaries are considered when managing the impacts from feral pigs on wetlands.

Additional information

• Find out more about the ecology of feral pigs.
• Defining metrics of success for feral pig management - Northern Australia Environmental Resources Hub, James Cook University, Deparment of Environment, Science and Innovation, CSIRO
• Feral pig population control techniques
• Wetland pests - WetlandInfo
• Feral pigs - Queensland Government
• Threat abatement plan for predation, habitat degradation, competition and disease transmission by feral pigs (Sus scrofa) - Australian Government
• Various reports on feral pig control and management - PestSmart
• Feral pig control methods humaneness matrix - PestSmart
• Impacts of feral pigs on tropical freshwater ecosystems
• National Feral Pig Action Plan – Information Hub
• National Feral Pig Action Plan 2021 – 2031

References

1. ^ a b c d e f g h i Australian Government (2017), Threat abatement plan for predation, habitat degradation, competition and disease transmission by feral pigs (Sus scrofa). [online], Commonwealth of Australia. Available at: https://www.environment.gov.au/system/files/resources/b022ba00-ceb9-4d0b-9b9a-54f9700e7ec9/files/tap-feral-pigs-2017-background-document.pdf.
2. ^ a b c Australian Pork Limited (2020), Australian Feral Pig Report - July 2020. [online], National Feral Pig Action Plan. Available at: https://feralpigs.com.au/wp-content/uploads/2020/07/National-Feral-Pig-Management-APL-Report-July-2020.pdf.
3. ^ a b Barrios-Garcia, MN & Ballari, SA (November 2012), 'Impact of wild boar (Sus scrofa) in its introduced and native range: a review', Biological Invasions. [online], vol. 14, no. 11, pp. 2283-2300. Available at: http://link.springer.com/10.1007/s10530-012-0229-6 [Accessed 11 January 2022].
4. ^ a b Bengsen, AJ, Gentle, MN, Mitchell, JL, Pearson, HE & Saunders, GR (April 2014), 'Impacts and management of wild pigs <i>Sus scrofa</i> in Australia: Wild pig impacts and management', Mammal Review. [online], vol. 44, no. 2, pp. 135-147. Available at: https://onlinelibrary.wiley.com/doi/10.1111/mam.12011 [Accessed 14 December 2021].
5. ^ a b Doupe, RG, Mitchell, J, Knott, MJ, Davis, AM & Lymbery, AJ (2010), 'Efficacy of exclusion fencing to protect ephemeral floodplain lagoon habitats from feral pigs (Sus scrofa).', Wetlands Ecology and Management, vol. 18, pp. 69-78.
6. ^ Freeman, AB, Strevens, W, Sebasio, D & Cann, J (2016), 'A preliminary assessment of the natural history and conservation status of the Jardine River Turtle (Emydura subglobosa subglobosa) in northern Australia', North Queensland Naturalist. [online], vol. 46, pp. 57-68. Available at: https://search.informit.org/doi/pdf/10.3316/informit.461283541284586.
7. ^ Hampton, J, Spencer, PBS, Elliot, AD & Thompson, RCA (June 2006), 'Prevalence of Zoonotic Pathogens from Feral Pigs in Major Public Drinking Water Catchments in Western Australia', EcoHealth. [online], vol. 3, no. 2, pp. 103-108. Available at: http://link.springer.com/10.1007/s10393-006-0018-8 [Accessed 11 January 2022].
8. ^ Kaller, MD & Kelso, WE (July 2006), 'Swine Activity Alters Invertebrate and Microbial Communities in a Coastal Plain Watershed', The American Midland Naturalist. [online], vol. 156, no. 1, pp. 163-177. Available at: http://www.bioone.org/doi/abs/10.1674/0003-0031%282006%29156%5B163%3ASAAIAM%5D2.0.CO%3B2 [Accessed 11 January 2022].
9. ^ Koichi, K, Sangha, KK, Cottrell, A & Gordon, IJ (2012), 'Aboriginal Rangers' perspectives on feral pigs: are they a pest or resource? A case study in the Wet Tropics World Heritage Area of northern Queensland', Journal of Australian Indigenous Issues, vol. 15, pp. 2-19.
10. ^ a b Mitchell, J, Experimental Research to Quantify the Environmental Impact of Feral Pigs within Tropical Freshwater Ecosystems. [online], Department of Environment, Water, Heritage and the Arts, Canberra. Available at: https://www.awe.gov.au/sites/default/files/documents/feral-pigs-impacts.pdf.
11. ^ a b c Natusch, DJD, Mayer, M, Lyons, JA & Shine, R (June 2017), 'Interspecific interactions between feral pigs and native birds reveal both positive and negative effects', Austral Ecology. [online], vol. 42, no. 4, pp. 479-485. Available at: https://onlinelibrary.wiley.com/doi/10.1111/aec.12465 [Accessed 19 January 2022].
12. ^ a b c Nordberg, EJ, Macdonald, S, Zimny, G, Hoskins, A, Zimny, A, Somaweera, R, Ferguson, J & Perry, J (October 2019), 'An evaluation of nest predator impacts and the efficacy of plastic meshing on marine turtle nests on the western Cape York Peninsula, Australia', Biological Conservation. [online], vol. 238, p. 108201. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0006320719305981 [Accessed 19 January 2022].
13. ^ O’Bryan, CJ, Patton, NR, Hone, J, Lewis, JS, Berdejo‐Espinola, V, Risch, DR, Holden, MH & McDonald‐Madden, E (February 2022), 'Unrecognized threat to global soil carbon by a widespread invasive species', Global Change Biology. [online], vol. 28, no. 3, pp. 877-882. Available at: https://onlinelibrary.wiley.com/doi/10.1111/gcb.15769 [Accessed 12 January 2022].
14. ^ Robinson, CJ, Smyth, D & Whitehead, PJ (October 2005), 'Bush Tucker, Bush Pets, and Bush Threats: Cooperative Management of Feral Animals in Australia's Kakadu National Park', Conservation Biology. [online], vol. 19, no. 5, pp. 1385-1391. Available at: https://onlinelibrary.wiley.com/doi/10.1111/j.1523-1739.2005.00196.x [Accessed 14 January 2022].
15. ^ a b Robinson, CJ & Wallington, TJ (2012), 'Boundary Work: Engaging Knowledge Systems in Co-management of Feral Animals on Indigenous Lands', Ecology and Society. [online], vol. 17, no. 2, p. art16. Available at: http://www.ecologyandsociety.org/vol17/iss2/art16/ [Accessed 14 January 2022].
16. ^ Russell, S, Ens, E & Ngukurr Yangbala Rangers (2020), '‘We don’t want to drink that water’: cross-cultural indicators of billabong water quality in remote Indigenous Australia', Marine and Freshwater Research. [online], vol. 71, no. 10, p. 1221. Available at: http://www.publish.csiro.au/?paper=MF19305 [Accessed 11 January 2022].
17. ^ a b State of Victoria Department of Environment, Land, Water, and Planning (2017), Impacts of pigs in wetlands. [online], Arthur Rylah Institute. Available at: https://www.ari.vic.gov.au/__data/assets/pdf_file/0036/66897/Impact-of-Pigs-on-Wetlands-Fact-Sheet-3.pdf.
18. ^ a b Waltham, N & Schaffer, J (2017), Continuing aquatic assessment of wetlands with and without feral pig and cattle fence exclusion, Archer River catchment. [online], vol. 17/04, Centre for Tropical Water & Aquatic Ecosystem Research (TropWATER), James Cook University, Townsville, Australia. Available at: https://www.researchgate.net/publication/320079038_Continuing_aquatic_assessment_of_wetlands_with_and_without_feral_pig_and_cattle_fence_exclusion_Archer_River_catchment/link/59d4c052a6fdcc181adc559f/download.
19. ^ Waltham, NJ & Schaffer, JR (2018), 'Thermal asphyxia exposure risk to freshwater fish in feral-pig damaged tropical wetlands', Journal of Fish Biology, vol. 93, pp. 723-728.

Last updated: 10 May 2021