Feral cats, rats widespread on Tinian as military-backed conservation expands across Marianas

Feral cats and rats are widespread across Tinian, posing significant threats to native wildlife and highlighting the scale of invasive species pressures in the Northern Marianas, according to a presentation on the fourth day of the 8th Mariana Islands Conservation Conference held virtually last March 17.

“Cats…were most recently surveyed in the ’80s, where their population was really limited to urban and surrounding tangan-tangan areas,” University of Washington researcher Kaeli Swift said. “But…we were seeing that cats were certainly not just in urban areas. They were everywhere, even breeding in interior forests.”

Swift said both species are now firmly established across the island, with serious implications for conservation.

“Rats and cats are the most common nest predators, with rats…being their primary nest predator,” she said.

Framing the broader context, Swift noted the vulnerability of island ecosystems.

“Islands represent less than 7 percent of global land mass, but contain about 20% of all of our species,” she said. “At the same time, we know that they’re also uniquely vulnerable.”

She added that invasive species remain a dominant driver of biodiversity loss.

“Eighty-six percent of all invasive attributed extinctions have occurred specifically on islands.”

Recent field data confirm just how widespread the problem has become.

“The big picture take home, again, we clearly have a lot of rats and now we know we also have a lot of cats,” Swift said.

Managing those populations remains a major challenge.

“There are so many rats on Tinian…if you can’t address food subsidies, it’s pretty darn hard to deal with rats in an area this big and when populations are as dense as we suspect them to be.”

At the same time, conservation efforts across the Marianas are increasingly being supported by U.S. military funding, particularly through Department of Defense-backed research.

“Knowing those species’ distributional ranges is fundamental for effective biodiversity conservation,” said Claudia Nuñez-Penichet of Virginia Tech, describing a project funded “with funds from DoD.”

Her team is developing species distribution models for threatened and endangered species across the archipelago to guide conservation planning.

“These species distribution models are going to allow us to identify high probability areas for discovering new species or new populations of that species,” she said.

The work is also aimed at improving how limited conservation resources are allocated.

“We don’t have unlimited resources and identify areas where many of the species might have suitable areas…can be very important at the moment of conservation prioritization.”

In Guam, military-supported conservation work continues to focus on controlling the invasive brown tree snake, a key threat to native birds.

“The goal of this project is really to support this recovery plan for the Mariana Swiftlet,” said Dusty Jordan of the Center for Environmental Management of Military Lands.

Efforts include managing snake predation and protecting nesting habitat around cave systems where the birds roost.

“In doing so, two of the things that are outlined in that plan is protecting roosting sites and nesting habitat and managing predation by the brown tree snake,” said Jordan, whose program operates under a cooperative agreement with DoD.

Across the Marianas, researchers say invasive species, limited data, and the need for sustained funding remain key challenges, even as new military-backed projects expand conservation efforts in the region.