Detection parameters for managing invasive rats in urban environments.

Area of Science:

• Ecology
• Invasive Species Management
• Pest Control

Background:

• Effective management of invasive ship rats (Rattus rattus) is hindered by limited ecological data in urban and peri-urban environments.
• Understanding rat behavior and detection probabilities is essential for successful eradication programs.

Purpose of the Study:

• To estimate ship rat detection parameters (σ, ε₀, θ, and g₀) in Wellington, New Zealand.
• To use these parameters in simulation models to determine optimal device spacing and surveillance strategies for ship rat eradication and confirmation.

Main Methods:

• Radiomarking of ship rats to collect data on their movement and interaction with detection devices (bait stations, chew cards, WaxTags).
• Utilizing simulation models to estimate eradication and surveillance parameters based on empirical detection data.
• Developing a predictive model linking detection distance (σ) and interaction probability (g₀) with individual variability.

Main Results:

• Mean home range radius (σ) was 25.37 m (1.21 ha); mean nightly encounter probability (ε₀) was 0.38; mean interaction probability (θ) was 0.34; mean nightly interaction probability at home range center (g₀) was 0.13.
• Simulations indicated that a 25 m × 25 m grid of bait stations for ~500 days could achieve eradication.
• Confirmation of eradication requires 3.25 chew cards/ha or 3.75 WaxTags/ha for 14 nights, with densities halved under specific conditions (e.g., 28-night surveillance).

Conclusions:

• The study provides empirically-derived parameters for optimizing ship rat eradication strategies in urban settings.
• Recommended device spacing and surveillance densities offer a framework for efficient and cost-effective pest management.
• Adaptive revision of device density based on habitat-specific detection is advised for enhanced program success globally.