Tiny Monito Gecko is Thriving and Proposed for Removal from Endangered Species List

Monito Island off the eastern coast of Puerto Rico. Map by Roy Hewitt, USFWS.

Monito Island off the eastern coast of Puerto Rico. Map by Roy Hewitt, USFWS.

Bombs and artillery shells rained down on them for years, but they survived.

Rats preyed on them, but they survived.

The Monito gecko is a resilient little critter. Living only on one small chunk of rock in the Caribbean Sea, the lizard has become so abundant that the U.S. Fish and Wildlife Service (Service) is set to make a decision later this year about its listing status under the Endangered Species Act.

“Our population surveys indicate that the gecko is thriving on Monito Island, the only place it is known to exist,” said Cindy Dohner, Southeast Regional Director for the Service. “Based on the most recent conservation actions and surveys, we believe that the Monito gecko may be recovered and the Service is planning on proposing delisting.“

A grey gecko blends into the surrounding limestone.

An adult Monito gecko is smaller than a human finger, and is known to exist on only one island in the world, off the coast of Puerto Rico. Photo by Jan Zegarra, USFWS.

About an inch and a half long, an adult Monito gecko (Sphaerodactylus micropithecus) can stand on your index finger with room to spare. It is named for its island habitat, a 36-acre uninhabited slab of limestone covered in scrub vegetation that juts sharply out of the sea about 50 miles west of Puerto Rico.

From 1940 to 1965, Monito Island was used for target practice by the Air Corps/U.S. Air Force as a bombing and gunnery range. Many bomb fragments remain, but it is unknown how much effect the bombs had on the gecko population or its habitat; the species was not even discovered until 1974. In 1965, the island was returned to the Commonwealth of Puerto Rico. The Service listed the gecko as endangered in 1982. It is uncertain how many geckos were on Monito at that time. One species that was clearly doing well, however, was black rats, which were island-wide in 1982 and considered an invasive species. Some scientists believed the rats were preying on the gecko, although there was not consensus. In 1992, the Puerto Rico Department of Natural Resources and Environment (PRDNER) began a black rat eradication and survey project on Monito Island using poison and traps, and the agency mounted a second poisoning campaign in 1999. Since those two projects, scientists visiting Monito Island have found no rats whatsoever.

Because the Monito gecko seems mostly nocturnal and spends its days hiding under rocks and inside crevices, population counts are challenging. Service and PRDNER scientists who counted geckos in 2014 and 2016 used a standard scientific plot survey and model to estimate there are now approximately 7,661 geckos on Monito.

Today, PRDNER continues to manage Monito Island as a natural reserve, protecting its wildlife and vegetation. In addition to its namesake lizard, the Island, which is closed to the public, harbors one of the largest seabird nesting colonies in the Caribbean, and is also home to the endangered yellow-shouldered blackbird and the Harrisia cactus.

“The recovery of a species is a very difficult but possible task that requires commitment and efforts of many sectors,” said PRDNER Secretary Tania Vazquez. “The results obtained thus far regarding the gecko on Monito Island suggest that its population is recovering. DNER will keep working with partners in this endeavor to assure the recovery of the species, its conservation and protection for future generations.”

Contact

Phil Kloer, philip_kloer@fws.gov
(404) 679-7299