Ag 2. THE IMPACT AND MANAGEMENT OF FERAL PIGS IN THE HERBERT CANE GROWING REGION OF NORTH QUEENSLAND By

The damage caused by feral pigs (Sus scrofa) in Wet Tropics canegrowing regions can be significant, with losses in cane proceeds exceeding $1M in certain years within the Herbert region. The management of the pest is difficult due to the landscape in which the feral pigs are found, the varying success of hunting, baiting and trapping activities and the overall intelligence of the pest being managed. In the Herbert, community partners have invested in managing this pest through a coordinated regional approach and research. The group utilises a multiple approach to manage feral pigs within the landscape through the use of GIS, genetic mapping and targeted on-ground activities. This paper will report on approaches adopted by the group and the research findings to date undertaken by the community partnerships group and funded by an SRA research project. Introduction Feral pigs are one of the most prolific and potentially the most devastating of Queensland’s introduced animal species. In Queensland feral pigs are a declared Class 2 pest, which means that they can potentially cause significant adverse economic, social and environmental impacts (Mitchell, 2011). Under the Federal Government Environmental Protection Biodiversity Conservation Act 1999, landholders are required to meet specific requirements to manage and control this animal pest species. Under Section 77 of the Queensland Land Protection (Pest and Stock Route Management) Act 2002, a landholder is required to take reasonable steps to keep their property free of feral pigs. Feral pigs can cause significant economic losses to specific cane properties in the Herbert region through the destruction of cane crops and damage to farm infrastructure like headlands and drainage systems. The economic loss caused by cane damage and decreases in CCS (commercial cane sugar) due to deteriorated cane, can exceed $1M to the Herbert cane industry in some years. No standalone management technique is believed to be effective to fully control feral pigs. Several techniques (like trapping, baiting and hunting) have been found to be effective in the control of feral pigs, however technologies like GIS and DNA population mapping can assist land managers to better manage feral pig populations. When developing a control management strategy the land manager must consider the problem being caused by the pig and implement the appropriate combination of control options to manage the problem (Mitchell, 2011). In the Hinchinbrook Shire Council area, a feral pig management program exists through investment made by various community partner groups, the cane industry (through Herbert Cane Productivity Services Limited), Hinchinbrook Shire Council, Terrain NRM, forestry companies and State government agencies. An SRA funded Grower Group project -‘An integrated feral pig management for the Herbert cane area’commenced in 2012 to investigate various and alternative methods to better control and manage feral pigs in the Herbert cane growing region, situated within the Hinchinbrook Shire Council area. This paper will report on activities undertaken as part of this project. Material and methods The project assessed various control methods, alternative baits to attract feral pigs, the use of pheromones, and the use of genetic population mapping, cane variety impacts and habitat influences. The research trials were established in three different locations throughout the Herbert River cane region to assess management strategies for varying landscapes and topographies. The locations were the Lannercost area, the Hawkins Creek area and the Coldwater area. The Lannercost area is predominately open cane land adjacent to grazing and forestry plantations. The Hawkins Creek area has cane land situated between the World Heritage listed rainforest (managed by National Parks) and the Herbert River. The Coldwater area is located adjacent to State owned and managed forested land; the country is broken up by gulleys and creeks. These locations were selected due to their diversity of habitat, their long history of cane crops being damaged by feral pigs and the cooperation of the landholders in the area. As a part of the project the influence of habitat adjacent to cane lands was assessed. In each of these three locations various control methods (trapping, dogging and baiting using a commercially available feed dispensing unit, HogHopperTM) or various bait materials were assessed. Numerous trial sites were established to assess the effectiveness of each method in each location. Pheromones were also assessed for their usefulness and ability to attract feral pigs. As a part of the project genetic material from pigs captured and killed in the shire was collected and forwarded to the Queensland University of Technology (QUT). A total of 264 feral pig tissue samples were obtained from 76 locations in the Herbert River region for analysis. Microsatellite DNA markers are extremely useful tools for examining population genetic questions of this nature and have been applied in a number of feral pig genetics studies (Hampton et al., 2004a, b; Spencer and Hampton, 2005). Microsatellites are highly variable, with rapid rates of mutation and are useful for revealing localised population structure. They consist of tandem repeats of short nucleotide sequences, are randomly distributed across the genome and occur at a high frequency in non-coding regions of eukaryotic DNA. Total DNA from samples sent to QUT was extracted using the salting-out methodology of Miller et al. (1988). Eight loci that have previously been shown to be polymorphic and unlinked in Sus scrofa (Alexander et al., 1996) were analysed in this study (SW240, SW632, SW857, SW911, SW936, SW951, S0002, S0068), following conditions outlined by Hampton et al. (2004a), and were resolved using an ABI3500 genetic analyser. A bayesian clustering approach implemented in STRUCTURE v2.3 (Pritchard et al., 2000) was used to estimate the number of populations (K) in a sample and to assign individuals to one or more of these populations (k). Ten runs of K = 1 to 25 was performed at 100 000 MCMC repetitions and 20 000 burn-in period using no prior location information, independent allele frequencies and a model of admixture. The posterior probability was then calculated for each value of K using the estimated log-likelihood to choose the optimal number of populations. Individuals were assigned to each of the inferred populations based upon the highest percentage of membership (based on the percentage of ancestry that can be attributed to each inferred population). Data on pig damage and incidence was collected from all farms involved with the research project. A HCPSL employed officer inspected all farms in the study area during the period from 1 June 2012 to 1 June 2013 for the presence of crop damage; multiple inspections were undertaken during this period on some farms were feral pig activity was high. Data on the cane variety, the percentage damage, adjacent habitat, crop age and other relevant information were collected and analysed. These data were used to assess the level of impact on particular cane varieties within the study area. Herbert Cane Productivity Services Limited (HCPSL) survey all cane growers in the Herbert annually for crop losses incurred by feral pigs. The data are geo-referenced to cane blocks and yield losses can be calculated. As a part of the project the economic losses were calculated using the data provided by growers. A field validation of reported losses by growers was undertaken by the project to validate the grower reported figures. The assessment required stalks from both the damaged and non-damaged locations within a block to be weighed to calculate a crop yield for each treatment. Results and discussion Control methods and bait materials The use of sodium fluoroacetate (1080) baiting method proved to be the most effective method in controlling feral pigs in the project area. Bananas and mangoes were found to be the best carrier for 1080. The 1080 is injected into the bananas and mangoes prior to being dispatched to the field. This finding agrees with Mitchell (2011) who reported that tropical fruits (like mangoes and bananas) were more effective than baits based on meat and grain in sugarcane production areas of the Wet Tropics. In the project, alternative bait materials like various grains, pineapples, PIGOUT®, worm castings, cat food biscuits, milk and bread were assessed (without the presence of 1080). Uptake by feral pigs of bait materials varied considerably in the field trials. In the trials the following observations were noted: no uptake of worm casting; limited to no uptake of grain based products (like maize, soybean and cowpeas), PIGOUT® and pineapples; and good uptake of cat food biscuits, milk and bread. The issue with the latter two bait materials are that they are not registered for use with 1080 and their use could have possible off-target impacts; the use of these products was discontinued and should not permitted in the future. Pineapples were eaten only in the area south of Ingham where pineapples are grown. PIGOUT® is a commercially available packaged bait for the control of feral pigs sold in Australia. One of the main reasons why the landholders were interested in assessing alternative baits, was because mangoes and bananas, which are the preferred baits, are not available at times. Mangoes are seasonal and there have been numerous times throughout recent history when bananas were not available for periods of 6-8 months (e.g. post cyclones Larry and Yasi). The research undertaken by the project and the wider Hinchinbrook Feral Pig Management program concluded that 1080 baiting accounts for over 55% of pigs killed, with the remaining 41% being due to trapping and 4% due to dogging practices, during the period of the 30 June, 2012 to the 1 July, 2013 (unpublished data). To date, hunting (especially dogging) has been foun