National Feral Pig Current Distribution in Australia

An integrated species distribution model was used to create this dataset. The model integrates different types of feral pig data: ‘presence only’ (PO) data, which consists of opportunistic and unstructured observations of feral pigs from citizen science programs, biodiversity data atlases, feral animal control programs and other sources, and ‘presence-absence’ (PA) and ‘abundance-absence’ (AA) datasets that are derived from structured surveys, including camera trapping and aerial survey programs. These were collated from Australian, state and territory government agencies and other sources ranging from research institutions to citizen science platforms. A full list of data sources is provided in the metadata.

To estimate the current distribution of feral pigs across Australia, conditional on the available data, five environmental covariates representing the basic needs of pigs were used (maximum temperature, distance to water, soil moisture, green vegetation and woody cover), along with a spatial random effect. The spatial random effect accounts for patterns in the data that are not explained by the covariates including spatial dependence in the current distribution of feral pigs (i.e., pigs are more likely present or abundant at locations nearby other locations where they are present or abundant, and vice-versa) due to dispersal constraints or management effects. A more detailed description of the modelling methodology is provided in the metadata.

The Tasmanian mainland was excluded from the modelling as feral pigs are not currently established there, and Kangaroo Island was excluded as the previously significant population of pigs on the island has been subject to an intensive eradication program. Australian offshore islands were excluded from the dataset, with the exception of the Tiwi Islands (Northern Territory) and Flinders Island (Tasmania), which have established pig populations of national importance.

This modelled dataset should be used as a broad-scale estimate of the current spatial distribution and relative abundance of feral pigs in Australia. It should not be used to plan local-scale control or monitoring efforts. Feral pig distribution is modelled at a national scale, using a 5 km x 5 km grid, and therefore does not reflect patterns of distribution and abundance that are influenced by environmental variation at finer scales.

This dataset does not estimate feral pig abundance on an absolute scale, but rather a relative scale. This is because information about imperfect detection and sampling design effects (in some data types) was not available and thus not accounted for in the model. The best estimate (median of the posterior distribution) and the lower and upper bounds of the 95% confidence interval (i.e. the 2.5% and 97.5% percentiles) of the estimate are provided. Larger differences between the lower and upper bounds indicate lower certainty.

The dataset is unlikely to accurately reflect the current feral pig distribution and abundance where recent lethal suppression efforts, eradication programs, range expansions, or accidental or illegal releases have taken place, as the data available for modelling inherently lag the true current abundance and distribution of the species. For example, the Victorian government advises that the population of pigs occurring at Quail Island in Western Port Bay in Victoria has recently been eradicated, although it is estimated as present in this map. In addition, the dataset is a static estimate of the current feral pig distribution from all available data that does not account for the fact that pig populations undergo boom-and-bust cycles in distribution and abundance due to wet and dry conditions.

Records of feral pig occurrence (presence or absence) are few or non-existent in some parts of Australia and frequent in others due to spatial biases in where occurrence data are collected. Although the model does account for some of these biases, there are still limitations in the occurrence data and modelling methods that will affect the accuracy of the modelled dataset. Lack of occurrence data in particular areas may lead to local underestimation of feral pig abundance. It will also increase the uncertainty associated with the estimates in those regions. It is therefore important for users to examine the confidence intervals provided alongside median estimates to assess model uncertainty.

More information and updates about feral pig occurrence and abundance can be obtained from state and territory government primary industries and environment departments. The NSW Department of Primary Industries and Regional Development regularly produces maps of feral pig distribution and relative abundance in NSW, based on consultation with land management organisations, including the NSW National Parks and Wildlife Service and Local Land Services. CSIRO, Australia’s national science agency, in collaboration with the Queensland Department of Primary Industries, has produced models of potential feral pig density and feral pig habitat suitability across Queensland.

This dataset was produced from a collaboration between the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES), the Commonwealth Scientific and Industrial Research Organisation (CSIRO), and data contributors, as part of the National Vertebrate Pests and Weeds Distribution Project. ABARES collated, cleaned, and standardised feral pig distribution data from government agencies and other external sources. CSIRO developed the integrated species distribution methodology and applied it to the feral pig data, leading the decision making required to produce the map using this methodology, with input from ABARES. Guidance for this project was provided by a steering committee comprising representatives from environment and primary industries agencies from all states and territories. The project was supported with funding from the Australian Government Department of Agriculture, Fisheries and Forestry’s Established Pest Animals and Weeds Management Pipeline Program and Supporting Communities Manage Pest Animals and Weeds Program.

Australian Bureau of Agricultural and Resource Economics and Sciences & Commonwealth Scientific and Industrial Research Organisation, 2024, National Feral Pig Current Distribution in Australia (2024), Australian Bureau of Agricultural and Resource Economics and Sciences, Canberra, December, DOI: https://doi.org/10.25814/rp6a-h992. CC BY 4.0