Seasonal habitat use by feral pigs (Sus scrofa)in the Arafura Wetlands and their impact on contemporary Aboriginal bush food resources

Abstract

Feral pigs (Sus scrofa) are a major environmental problem in many parts of Australia. As habitat generalists they have successfully colonised and continue to spread across a very wide range of environments. The environmental damage pigs cause has only recently begun to be quantified and our understanding of the impacts they have on habitats and biodiversity remains limited. Feral pigs are threatening the environmental integrity (see page 16 for definition) of the Arafura Swamp and catchment in north central Arnhem Land, Northern Territory. They are also impacting on local bushfood resources and other aspects of the lives of Yolngu, the local Aboriginal people. Without control, feral pigs are likely to continue to thrive in the Arafura area and cause further changes to the country that is so important to Y olngu people. A broad, holistic approach to feral pig management has been adopted here by engaging two systems of knowledge - western scientific and traditional Aboriginal ecological knowledge - and their interactions with one another and the unique study area. This study focussed on feral pigs, as their impacts on Yolngu way of life are a current issue to these people. In addition, preliminary research into the impacts of Asian water buffalo (Bubalus bubalis) was undertaken, given the probable (and significant) future effects of this species on the land and its people. A key objective of this thesis was to determine and quantify the seasonal use of habitats by feral pigs and buffalo in the northern Arafura Swamp and the key environmental attributes that drive their activity. Signs of presence and activity of feral pigs and buffalo were recorded in a range of habitats over a 12-month period together with potential environmental correlates. These data were used to develop a predictive model of seasonal feral pig activity that would enable optimisation of control measures through knowing which locations to target at particular times in the seasonal cycle. The results from this study suggest that pigs are widely distributed in the northern Arafura wetlands and immediate surrounds and are using a broad range of habitats throughout the year, which often vary with season. Some habitats are used all year round but serve different functions according to season. Seasonal variation in habitat use by pigs was largely in response to annual flooding and drying and the consequent influence of this on resource distribution and abundance, and then by a series of other environmental variables. Intense productivity and the distribution patterns of permanent water throughout the area may explain the preference pigs show for wetland habitats throughout much of the year. While detailed modelling of buffalo activity patterns was not undertaken, activity was widespread across the study area in the late and mid dry seasons and was restricted during the wet season by the presence of extensive floodwaters. It is probable that the broadest criteria (in a landscape sense) for seasonal variation in pig habitat use would also apply to buffalo. Before feral animal management can be considered, it is essential that there is an understanding of stakeholder perceptions and aspirations regarding these animals and the effects that they have on the natural environment. These views can play a significant role in the success or failure of a pest control program. The cultural and local political environment of the Arafura wetlands also plays an enormous role in determining appropriate management strategies for this area. Thus, a second objective of this thesis was to determine Yolngu perceptions of feral pigs and buffalo and their impacts on custodial lands and to understand Yolngu aspirations regarding the management of these animals. Qualitative methods were primarily used in this part of the research. A combination of participant observation and semi-structured interviews was used to collect information about individual and community perceptions of feral pigs and buffalo. There was a diversity of both views and of understanding about feral pigs and buffalo and their management. A range of social (by way of relationships) and external factors have influenced the perceptions held by Yolngu in the northern part of the swamp. While there were different views about the degree of impact feral]pigs have on land and resources amongst those Yolngu involved in this study, most expressed some concern about the effect pigs were having on land and bushfood resources. All were keen to implement some degree of control and most expressed a desire for complete eradication of feral pigs. However, less concern was expressed about the effects of buffalo and fewer people thought that they should be controlled. The reasons for this included the value of buffalo as a food source and the length of time that buffalo have been present in the area. Bush foods and subsistence activities are still very important to YoAngu both in a dietary sense and for maintaining culture. Y olngu were concerned about the effects of pigs on bushfood resources and believed that increased competition for these food resources has led to a reduction in their availability. These concerns were documented as part of this study. In addition, analysis of the overlap of seasonal pig activity with key areas for resource production was undertaken. My findings are that feral pigs and buffalo have disrupted some of the certainty about bush food availability that Y olngu have depended on over their many years of occupation of the area. People are justifiably concerned about the effects of these feral animals. There is spatial overlap in the places where people and pigs obtain many of their seasonal food resources and pigs do appear to consume many resources that are important foods for Yolngu. Consequently there is increased pressure on resources in these areas. Feral animal management strategies must have local context and ownership and as such, Yolngu representatives need to play a key role in development of these strategies in the northern Arafura Swamp to ensure that outcomes are consistent with the social, political and cultural aims of the community. Management recommendations were developed based on the seasonal models of feral pig activity and community-based management was suggested as a key element of feral pig control. In conclusion, this study demonstrated that feral pigs are active across a broad range of wetland and surrounding habitats and are having a significant effect on Yolngu. It would appear that feral pigs may fundamentally alter people's relationships with the land; most outwardly by affecting the subsistence economy, but also by affecting other relationships to the land including comprehension of the physical landscape and responsibility for maintaining healthy country. The results suggest, and Yolngu custodians involved in this research agree, that the significant effect that pigs are having on this landscape and its people warrants the implementation of strong and effective control measures. The findings from this study are important for the Y olngu people and their local environment, but also provide a benchmark for other areas and other problems by showing the value of collaborative engagement. This research demonstrates the benefits of working closely with Aboriginal people to determine management strategies that are appropriate to local context. It highlights the need for a robust understanding of the complexity of the situation and diversity of opinion, which requires an in-depth understanding of the local social and political arena.