About

TrapSim Plus is a computer model that simulates lethal removal of invasive species using ground-based control methods such as kill-traps and bait-stations. It is designed to simulate control for six of New Zealand's main invasive predator species: brushtail possum, stoat, ferret, weasel, ship rat, and Norway rat.

The purpose of TrapSim Plus is to provide managers and communities with guidance for designing and costing control and eradication strategies for invasive mammals. It is aimed at helping users answer three key questions:

  • For a given level of funding, what change in pest numbers is likely to be achievable?
  • For a specific goal, how much control effort, and therefore, cost, is required?
  • Of all possible scenarios (device type, number of devices, duration), which is likely to be the most cost-effective approach?

It allows users to specify a number of different scenarios by varying the level of control (e.g. number of devices and duration of control), and simulating the outcomes. The relative changes in pest numbers and the costs of each scenario can be used to help determine the most cost-effective strategy that meets a programme's goals.

TrapSim Plus is an extension of the original TrapSim (Gormley & Warburton 2017) which was developed as a simple to use online tool for simulating trapping of vertebrate pests, and was adapted from the model of Glen et al (2017). TrapSim was written in the R programming language and deployed using the 'Shiny' package.

It should be noted that TrapSim Plus is a simplified model of reality. There are many features that are not accounted for, such as individual variability, immigration, and changes in animal behaviour over time. As such, the model predictions will invariably differ from reality to some degree. The tool is NOT designed to predict the exact number of individual pests remaining after a control programme but to compare the relative cost-effectiveness of a range of approaches to reducing pest numbers over a defined area. Its utility is in helping us understand a system and providing insight when comparing the relative effectiveness of a management activity, and ultimately helping to guide managers and communities in their decision-making.

References

Glen, A.; Latham, M.; Anderson, D.; Leckie, C.; Niemiec, R.; Pech, R. & Byrom, A. (2017). Landholder participation in regional-scale control of invasive predators: an adaptable landscape model. Biological Invasions. 19, 329-338.

Gormley AM, Warburton B. (2017). TrapSim: A decision-support tool for simulating predator trapping. Landcare Research Contract Report LC2993