1. USAF, USFWS, and Island Conservation Attempt to Eradicate Rodents at Wake Atoll
18-Sep-18
As of:

2. Wake Atoll

3. Goals and Approach Goal: Approach:
Remove 100% of the rodent population (Rattus exulans & Rattus tanezumi) from all three islands (Peale, Wilkes and Wake)
Approach:
Award project to USFWS via intergovernmental fund transfer
Utilize biological window for operation; maximize exposure to targets and minimize exposure to non target species
Apply two applications of Brodifacoum 25w (85,000 lbs) to all three islands via bait stations, hand and aerial broadcast
Implement USAF biosecurity plan and monitor

4. Baiting Methods
Hand Broadcast, bait bags, aerial broadcast with a bait bucket , and bait stations

5. A total of 37,423.13 kg of Brodifacoum was used
Bait Rates
Orange areas indicate areas where bait stations had to be used, everything else was bait by the helicopter
1821 acres A
A total of 37, kg of Brodifacoum was used

6. Baiting Exclusion Zones
Target App Rates:
App 1: 18 kg/ha
App 2: 9 kg/ha
Large Exclusion Zones
Areas in orange show areas that had to be treated differently from standard aerial methods
60 ha excluded
1,344 Bait Stations in 266 buildings
607 Abandoned Structures

7. Environmental Challenges
737 ha of ground to treat
Thick vegetation that was difficult to navigate
Large pemphis intertidal zones
12 Miles of shoreline
700 ha approximately surrounded by a lot of water

8. Environmental Challenges
Natural Food Competition
Non – Target Consumption
Natural food availability

9. Commensal Challenges Food Sources from the Chow Hall and Dorms
Food Availability from the Disposal Facility
Commensal component

10. Structural Challenges
Underground Utilities
Large Historic and Complex Infrastructure
There were known and unknown underground infrastructure
Large and complicated infrastructure required special treatment, many abandoned buildings, and underground structures, not mapped

11. Installation Challenges
Years of Old Debris
Operating on and near an Active AF Runway
There were many acres of old rusted debris that made sowing in with hand bait very difficult and dangerous
A FOD walk had to be done on both runways after each aerial application (very time consuming)
AF regulations about hot re-fueling on the tarmac

12. Logistical Challenges
Getting a private helicopter and all the supplies needed to such a remote military installation

13. Mechanical Challenges
Unknown bait rate applications from faulty equipment

14. Rat Sightings Post Application
1 June Rat – was considered a mummified rat and was not source of concern
25 June 2012 – A rat was run over near the golf course
A Rapid Response Team was deployed twice after June and spot treated all 6 areas

15. Post Aerial Application of Brodifacoum Determinations
3 rats recovered post application were confirmed to be Rattus exulans and of the same DNA makeup as the pre-application species
To date no Rattus tanizumis have been discovered on any of the 3 islands
To date neither R. tanizumi or R. exulans have been found on Peale
R. exulans have aggressively re-populated the atoll
Some bait was recovered within the shoreline
10% of fish tissue sampled tested positive for brodifacoum residual
Non-target take was considerably less than anticipated (only 6 birds)

16. Most Likely Causes for Unsuccessful Outcome

17. Rats Could Not…
All rats could not eat a lethal dose of bait (or a lethal dose via secondary consumption of other bait consumers) possible reasons:
There were gaps in coverage
There was insufficient bait for all rats because it was eaten by non-target species before rats were able to consume a lethal dose
Rats had a higher tolerance than expected to the toxicant

18. Rats Would Not… All rats would not eat a lethal dose
For some rats there was a bait aversion acquired from previous control efforts
For some rats there was a natural or learned aversion of bait stations
There was an inter-species competition that excluded some R. exulans either physically or behaviorally from accessing bait, particularly from bait stations
Some rats chose not to eat bait, or enough of it because of palatability of the bait and or availability of natural commensal food sources, and/or because of seasonal behavioral changes (e.g. breeding females confined to nests or smaller home ranges)

19. Bird populations post effort

20. Wake Island Rat Eradication
Questions?