A24 RMP
Reducing the impacts of invasive small mammals is an important component of natural resource conservation throughout Hawaiʻi. This Recommended Best Practices (RMP) from the Hawaiʻi Conservation Alliance is for the use of A24 automatic resetting traps manufactured by Goodnature (GoodNature.co.nz) and sold in the USA by Automatic Trap Company (https://www.automatictrap.com/). We provide a brief overview of rodent control and a "Quick Start Guide" for the use of A24s, cover safety and regulations, purchasing, procedures for planning and implementation, procedures for trap checking and data management. We provide additional recommendations and tips from predator control practitioners in Hawaiʻi. This document will track current next steps and future research needs. We will incorporate new information as it is developed and highlight challenges and needs as the practice of controlling rodents with A24s in Hawaiʻi continues to evolve. For more information, see the resources section.
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Background
In Hawaiʻi, A24 traps are used to humanely dispatch rats (Rattus rattus, R. norvegicus, R. exulans) to reduce predation of native plants and animals. Observations of A24 non-target species (mice and mongoose) kills are not unheard of. GoodNature manufactures a mouse shroud to adapt the A24 trap for controlling mice, however its efficacy and humaneness to target mice in Hawaiʻi has not been evaluated. For mongoose, the A24 may decrease in humaneness as full pressure of the trap decreases. GoodNature A18 model has been rated for mongoose control. This RMP is focused on the application of A24 for rats, based on recommendations from the New Zealand Department of Conservation and the professional experience of programs in the Hawaiʻi Conservation Alliance (HCA) and the Hawaiʻi Conservation community more broadly.
Quick Start Guide
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Determine how many traps you can afford, maintain, and fit into your site
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Traps should be deployed in a 100-meter by 50-meter grid. Larger grids with more traps will reduce the frequency and intensity of impacts to protected resources. Ultimately, grid design will vary depending on site specific rat densities and management goals. See Appendix 4 for more information and examples of grid design.
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Traps should not be attached to ʻōhiʻa trees to avoid damaging bark, especially where ROD is present
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Each trap should be installed 10-12 centimeters above the ground with a clear entrance
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Traps should be recharged with CO2 and new bait every 30-180 days. This will vary based on location and accessibility. See Table 1 for more information.
Table 1: Summary table of lessons learned and limitations experienced by NRM programs across the state
A. Some important things we have learned
1. A24 traps are more efficient in maintaining consistent control of rats than single-strike traps because they reduce the amount of labor needed to reset the traps.
2. Small grids with fewer than 5 traps are effective at reducing impacts to a small area (5 meters by 5 meters) with sensitive species. However, larger grids with more traps will reduce the frequency and intensity of impacts on protected resources over a larger area for a longer time.
3. Traps should be installed along access trails adjacent to sensitive areas to avoid direct impacts from trampling.
4. Areas with high rat density need to be serviced regularly to avoid rat damage to traps (Figure 1)
B. Some limitations we have seen
1. Traps need to be recharged with bait and CO2 every 30-180 days.
2.At higher elevations (>7000’), the ALP inflates and pushes out the bait at a higher rate, emptying in just 30-60 days
3. ALP batches may not inflate (see Appendix 2)
4. The bait can clog in the bottle and stop dispensing in dry climates. The bait can rot quickly and become moldy in wet climates. Birds, mollusks, ants, and other invertebrates will remove and consume the bait.
5. A24 in coastal areas may rust quickly and rust-prevention treatments may repel rats
6. The warranty period (2 yrs) starts when the trap is deployed however warranty is voided if NOT using manufacturer CO2 canisters.
7. KFRPB has documented common malfunctions and how to track (see Appendix 3)
Figure 1: Trap with severe rat damage from gnawing of trap body. Areas with high rat density must be serviced on time. This grid was checked a year late and each trap looked like this. Traps that run out of strikes still have an attractive lure inside, that rats will try to get to when desperate enough.
Regulations and Worker Safety
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