Principles of pest animal management

People decide whether an animal is a pest or not, and what is a pest  to one person may be a valuable resource to another. The pest  status of an animal can vary depending on the location, land use and  the values and attitudes of the people who are concerned with the  benefits and/or damage that the animal is causing.

For example, a  feral pig might be worth $100 AU at the point of sale where it is  processed into game meat for the European gourmet market, and  viewed as a valuable resource by the hunters and meat processors. Others believe that feral pigs are a menace to the environment and  agriculture, and should be controlled regardless of its value. The pest status of an animal can also vary over time and with the  same observer. For example, some banana growers in Queensland  view feral pigs as a major pest when banana prices are high but a welcome guest when prices are low, as they clean up fallen fruit that  can be a disease source to the crop.

Different groups and individuals have different attitudes towards  pest animals and how they should be managed, and this can  determine success or failure of a pest management program. When  planning pest management it is essential to consult those people who are affected by pest damage as well as those who might be  affected by or need to be involved in pest management activities  (see Planning strategic pest animal management). This is a two-way process where the landholders’ attitudes towards the pest  and management options must be understood and valued equally to  that of other stakeholders, such as government agencies that  regulate pest management. Consultation requires active engagement, open discussion, and the development of trust  between all parties. This is especially important where programs  need to be coordinated across a broad landscape (eg wild dog  management), requiring a range of landholders and groups to be  involved. If several land managers within the landscape do not cooperate and actively stop  management, such programs can be ineffective.

When trying to work out the dimensions of a pest problem it is  important to identify:

• who has the problem
• where the problem is and what is the extent of the damage believed to be caused by the pest
• what stakeholders want to do about it.

Building trust between diverse individuals and groups can be a difficult and time consuming process, but it is essential. Some participants may need to improve their knowledge and  understanding of pest animals and the available control options, in order to contribute and make an informed decision about  management.

The nil tenure or cross tenure approach can be a useful method for  reducing conflict and reaching decisions on cost sharing. This  process involves key stakeholders coming to a joint understanding about the damage that pests cause, knowing where pests move  throughout the landscape and where to implement management  using a map with no tenure boundaries.

Once a pest population is established, eradication (ie complete and  permanent removal of a pest) is difficult to achieve. It is therefore  essential to minimise the risk of new pests entering a region and to  quickly remove individuals before they have a chance to spread and  establish breeding populations if they are found in the wild (Figure 1, right). This is the ‘Prevention’ stage of the ‘invasion’, where the area  occupied by the pest is small and the economic return of  management is high. The second stage, ‘Eradication’, is only possible  on some islands or where pest populations are very small and  isolated (see Rabbit eradication on offshore islands). This is because a successful eradication program must ensure: i) that the  control operation can remove the pests faster than they can  reproduce, ii) that immigration of pests from another area or source  can be prevented, and iii) that all reproductive individuals are able to be taken by the control  techniques available. Meeting these criteria is rarely possible and/or very difficult to achieve over a large area.

When a pest species can no longer be eradicated or contained  because they have spread and multiplied in number, management  switches from a focus on the pest itself, to ‘asset protection’ — or  reducing the damage that pests cause to assets, to an agreed, acceptable level. While it is relatively cheap to remove an individual  pest when overall population densities are high, there comes a point  when removing pests becomes more expensive than the benefits gained. The point at which the cost of management outweighs the benefits can be difficult to determine, however an effective  monitoring program should help determine if and when this point is reached (see Principle 7 and Monitoring and evaluation).

Pest animals are one of many land management problems that can  affect agricultural production and biodiversity. Weed and water  management, habitat quality, livestock genetics, nutrition, climate and rainfall can also influence desired land use outcomes (eg conservation of endangered wildlife, see Box 1). It is important for  land managers to consider the function of the overall system when  deciding where to use limited resources to achieve the best  outcomes.

Managing the whole system — pest management for conservation

Malleefowl (Leipoa ocellata) are preyed upon by foxes. One study found that there was little recovery in Malleefowl numbers after extensive poisoning of foxes. A later study showed that, although foxes were important predators, Malleefowl numbers did not increase after fox control because the necessary food for chick survival was not available. Managing grazing by domestic stock, feral goats and rabbits to restore native grasses and their seeds on which the chicks fed was as necessary as reducing fox predation for Malleefowl population recovery.

Other factors can add to the complexity of pest management, such as:

• the biology and behaviour of the pest and the affected wildlife, livestock and people
• the availability of control techniques
• the variable interests of the key stakeholders
• cost:benefit ratio of management actions.

By placing pest animal management in the context of a whole system, land managers gain a better understanding of the impacts of  pest animals, and can focus on managing all resources to achieve  the best outcome.

It is important to acknowledge that our understanding of these  complex and dynamic systems is incomplete, so it is difficult to know  how the system will respond to management actions or whether  desired outcomes will be achieved. An adaptive approach to  management takes this into consideration, enabling land managers  to monitor and evaluate the effects of management, and adapt their actions accordingly.

It is essential to monitor the effects of pest management actions, and to evaluate whether these effects are producing the desired  outcomes. A monitoring and evaluation plan provides critical information that can guide future management decisions, such as whether the program needs to be modified or how it might be made more efficient; or whether the pest is actually causing the damage, or if there are more significant factors at play (eg poor livestock genetics causing lamb mortality). Monitoring can be resource intensive so it is important to determine:

• what data needs to be collected
• when or how often it needs to be collected (eg every day, once a month)
• where it should be collected (eg photopoints)
• how it will be collected and used (eg camera traps, photopoints,  live trapping, vegetation surveys). See Monitoring and evaluation.