House mouse predation on nesting albatrosses at Midway Atoll NWR 2015-presentMeg Duhr-Schultz, USFWS

• Discovery

• Impacts HY16 and HY17

• Impact monitoring

• Ecological context

• Current control efforts

• Next steps

Initial discovery of predatory mouse behavior at Midway Atoll in 2015

Dec. 23 Bird counters observe 5 nesting Laysan albatrosses with blood and wounds on their head and necks in a small, localized patch

Dec. 24 USFWS Staff investigate. Expanded search effort yields 20 injured birds. Staff initiate regular patrols of area to mark impacted nests. Dawn and dusk observations to find cause of the injuries conducted.

Dec. 24-Jan. 4: Number of injured birds growing by the day. First mortalities detected. Wildlife health experts consulted. Still no culprit, rodents suspected.

Jan. 5: Three Reconyx night vision trail cameras and 8 live traps deployed at impact area.

Intensive patrols and observations of every bird reveal a situation far more severe than initially thought.

Zone A Monitoring HY2016-nests marked, both adults received temporary band, chicks also banded-follow fate of nest through season and fate of adult (healing, injured, etc.)-after 5 weeks of intensive monitoring 97 nests, egg failure rate was over twice the rate found in our long-term repro. plots.

Zone C Monitoring

1. What is the rate of attack?2. How fast does the behavior spread

through an area? 3. How are individual birds responding

to the attacks?4. How often are both mates of a pair

attacked?5. How does this impact breeding

success?

• Intensively monitor 40 nests: 20 nests with at least one bitten adult, monitor the nearest adjacent nest with an unbitten bird.

• Apply temp. bands to each mate, objectively assess status of injury every day

Zone C Monitoring Data

12 bitten birds detected Jan 20. Daily monitoring of 40 nests in impact area initiated.31 bitten birds in plot by Feb. 5.Mouse control implemented Feb. 4.

How can a half ounce mouse kill a 7 pound adult albatross?

• Repeated stress reduces fitness and ability to heal from with physical injuries

• Localized and systemic infections originating at the wound site

• Fending off mice incurs a high energetic cost during periods when birds should be recovering from long foraging trips

Necropsies• 6 carcasses sent to USGS-National

Wildlife Health Center Lab on Jan. 6; rodent attacks confirmed and substantial tissue damage and sub-dermal hemorrhaging noted

• Additional 24 freshly dead birds necropsied on site. Tissue sets sent to lab for histology.

Initial observations in field• All birds had healthy layers of body fat

and well developed pectoral muscles.• Gross changes suggestive of sepsis

observed in majority of necropsied birds. No signs of trauma or cause of infection evident other than large bite wounds

Histology results • Cause of death was infection in blood

or muscle tissue secondary to the bite wounds.

(Dr. Thierry Work, pers. comm. 2016)

BeforeHave recent changes in landcover left house mice resource-limited?

Verbesina enceliodes is in the sunflower family (Asteraceae), plants which typically have protein rich seeds.

2011% Cover

± SE

2015% Cover

± SE %Change

t-test p-value

Sand, etc. 9.0 ± 1.3 45.0 ± 3.3 400.4 0.00Native 8.2 ± 2.2 10.1 ± 2.7 23.4 0.41

Nonnative 15.1 ± 2.0 44.1 ± 3.1 192.2 0.00

Verbesina 67.7 ± 4.0 0.7 ± 0.1 -98.9 0.00

Sand Island % Cover 2011, 2014, 2015(Klavitter, et al. 2016)

1991

2004

(Laniawe 2004)

Dec. 2014

Atypical rainfall patterns 2015 and 2016

• 40 m x 40 m initial response bait grid deployed on Jan 8

• Full grid implemented on Jan. 25• Total area: 11,688 square meters• 514 pieces of mouse control equipment (wire

traps, multi-catch traps, and bait boxes)• checked and re-baited daily by staff and

volunteers (8 person hours/day)• 180 mice caught between Jan. 25 and Mar. 7• Last albatross attack documented on Feb. 5

Mouse control in attack zones

Objective: localized mouse density reduction to stop or slow attacks on nesting adults in the years before eradication can take place

Method: hand broadcast of pelleted rodenticide (active ingredient: Cholecalciferol) along a 5 meter grid at a rate of 20 kg/ha.

Treatment 1: December 17-18

Treatment 2: January 18-20

Treatment 3: date TBD and will be based on field monitoring and mouse/chick interactions.

Mouse impacts to albatrosses 2015-present

Hatch Year 2016

First detected on: Dec. 23, 2015

Number of discrete impact areas: 3

Number of isolated bitten or dead birds: 0

Total area of impact: 1.65 hectare

Minimum total impacts (Dec. 23-Feb. 29): Adult fatalities: 42Nests abandoned: 70Active nests with bitten birds: 480 nests

Monitoring approach: inventory total known mouse attacks, follow nests to document impacts to adults and breeding success, necropsies to determine mechanism of injury, monitor rate of spread and attack rate

Response: control grids over 3 impact areas with combination of live traps and bait boxes at 5 meter spacing

Hatch Year 2017

First detected on: Dec. 4, 2016

Number of discreet impact areas: 50

Number of isolated bitten or dead birds: 35

Total area of impact: 11 hectares

Minimum total impacts (Dec. 4-present): Adult fatalities: 242Nests abandoned: 994Active nests with bitten birds: 1218

Monitoring approach: focus on detection and mapping of attack zones to best inform treatment, monitor efficacy of bait application

Response: hand broadcast of low-toxicity pelleted bait along a 5 meter grid of each impact area+buffers every 3-4 weeks until attacks cease

0

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-2 1 4 7 10 13 16 19 22 25 28 31 34 37 40

(Approximateremainingalbatrossincuba onperiod:days20to60)

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Next steps: • Logistics and planning for pre-emptive bait

applications in known impact areas in HY2018 before adults begin nesting.

• Island Conservation contracted to lead eradication feasibility studies. Initial site visit completed in Nov. 2016.

• Applying for USFWS Large Invasive Species Grant for mouse eradication in 2018 and engaging NFWF, NWRA, ABC and other partners for additional funding support.

• Planning on and off-island overhauls in biosecurity, commensal rodent management, and waste management practices in preparation for eradication.

• Special studies on-island in: bird-airstrike hazards, mouse population dynamics, biomarkers studies on bait pallatability and uptake

• NEPA support is funded and underway

Minimizing impacts to non-target species during an eradication operation: critically endangered Laysan ducks and migratory shorebirds

• MBTA compliance and Section 7 consultations• Laysan duck studies to investigate timing of molt,

techniques for large scale capture and captive or semi-captive rearing

• Shorebird migration timing• Bristle-thighed curlew monitoring

Thank you!

Many sincere thanks to USFWS Pacific Islands Refuges and Monuments Staff, USFWS R1 Branch of Refuge Biology, USFWS Office of Migratory Birds, National Wildlife Health Center-Honolulu Field Station, Chugach-DBSI, Bell Labs, Island Conservation, the National Fish and Wildlife Foundation, and the US EPA for immeasurable logistical, technical, and moral support.

Most field work was carried out by Midway Biology volunteers—a small army of extremely dedicated and talented people without whom we would not be able to respond to invasive species crises.

January 14-16, 2017

January 14-16, 2017

January 14-16, 2017

January 14-16, 2017