Invasive Rats Found on Five Virgin Islands Cays

A survey of six offshore cays in Virgin Islands National Park found black rats on five and green iguanas on one.

Updated on Nov. 6, 2026 in Wildlife

Low scrub-covered offshore cay with pale limestone outcrops above turquoise shallows, with seabirds overhead under bright tropical light. — U.S. wildlife teams found invasive black rats on five of six surveyed Virgin Islands cays, threatening seabird nesting, in a December 2025 survey. AI Illustration. Upload story photo >

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U.S. wildlife teams surveyed six offshore cays in the U.S. Virgin Islands for invasive species in December 2025. Black rats were recorded on five of the six cays and green iguanas on one.

Why it matters

Black rats prey on seabird eggs and chicks, which can cause failed nesting and declining seabird populations on islands that have historically supported colonies. The findings point to a potential need for removal efforts to restore nesting habitat.

Black rats were recorded on five of the six offshore cays surveyed, while green iguanas were found on one cay. The survey covered cays managed by Virgin Islands National Park, and the total population sizes of these invasive species were not reported.

The players

U.S. Fish and Wildlife Service

The federal agency that leads wildlife conservation and habitat protection across the United States and its territories, including the Caribbean Coastal Program that led this project.

Island Conservation

A nonprofit organization that works to remove invasive species from islands to protect native wildlife and ecosystems worldwide.

Virgin Islands National Park

The national park on St. John that manages the six offshore cays included in the survey.

The details

The project was led by the U.S. Fish and Wildlife Service's Caribbean Coastal Program in partnership with the nonprofit Island Conservation, and received its first funding in 2024. Biologists reviewed older seabird survey records alongside fieldwork conducted in December 2025, with support from national park staff and Friends of the Virgin Islands National Park.

2024: The project received its first funding.
December 2025: Fieldwork for the assessment was carried out.

Seasonal Patterns

The Caribbean Coastal Program's invasive species work targets offshore cays where seabird colonies have historically nested. The survey adds the Virgin Islands to the broader regional effort, which also includes sound-attraction seabird restoration at Desecheo Island National Wildlife Refuge in Puerto Rico.

Invasive rats and iguanas can reduce the number of seabirds nesting on offshore islands, which affects visitors and residents who value these wildlife areas. Visitors to Virgin Islands National Park may see restoration efforts that temporarily change access to some cays while removal work is carried out.

The takeaway

Invasive predators can quietly reduce seabird nesting success long before population declines are visible, so monitoring offshore islands matters. Supporting local conservation groups and following park guidance on closures helps protect nesting birds.