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Monito Island is an uninhabited and mostly inaccessible island of only about 36 acres. It lies west of Puerto Rico and was designated a U.S. National Natural Landmark in 1975. Photo by USFWS.

An endangered species recovery success story: Service proposes delisting Monito gecko following conservation collaboration

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

Non-native rats preyed on them, but they endured.

The Monito gecko is one resilient little lizard.

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

Living only on one small chunk of rock in the Caribbean Sea, the gecko has weathered adversity and is now so abundant, the U.S. Fish and Wildlife Service (Service) is proposing to remove it from federal protection due to recovery.

The proposal to delist the Monito gecko follows an effective conservation partnership between the Service and Puerto Rico that eradicated its primary threat, namely black rats that were accidentally introduced to the island. It also follows a comprehensive review of the best available scientific and commercial information about the species’ present and future status.

“This delisting is the latest recovery success achieved through partnerships with our state wildlife partners,” said Greg Sheehan, the U.S. Fish and Wildlife Service’s acting Principal Deputy Director. “I want to recognize the great efforts of our colleagues at the Puerto Rico Department of Natural and Environmental Resources, other partners, and our employees, who together helped guide this species toward recovery.”

About an inch and a half long, an adult Monito gecko can fit 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.

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.

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, and it is now managed as a nature reserve.

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 at that time, however, was the black rat, which occurred island-wide and preyed on the gecko.

In 1992, the Puerto Rico Department of Natural Environmental and Resources (PRDNER) began a black rat eradication and survey project on Monito Island using poison and traps, and the agency mounted a second eradication campaign in 1999. Since those two successful 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, but Service and PRDNER scientists estimate there are now more than 7,600 geckos on Monito.

“When species are recovered, we are committed to removing them from federal protection to reduce the regulatory burden on the public and industry and to ensure that the limited resources available to at-risk species go to those others still most in need,” said Sheehan.

Today, PRDNER continues to manage Monito Island as a nature 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 challenging task, but it is possible with the commitment and effort of the sectors involved. The proposed delisting of the Monito gecko is a remarkable achievement for all the partners who worked towards this goal. PRDNER will keep working with our partners to ensure the protection of the gecko for future generations,” said PRDNER Secretary Tania Vázquez Rivera.

Hurricanes, including recent Irma and Maria, are not considered a threat to the Monito gecko because the island is 66 meters above sea level, and thus safe from storm surge. The vegetation on the island is short and therefore hurricane impacts are expected to be minimal. Additionally, the Monito gecko is under rocks most of the time.

The Service is publishing a draft post-delisting monitoring plan in conjunction with the proposed rule. The Service and PRDNER will be the primary entities conducting the monitoring.

The Service is accepting public comments on this proposed delisting from Jan. 10, 2018, to March 12, 2018. We particularly welcome input from other government agencies, non-governmental organizations, the scientific community, industry, or other interested parties concerning this proposed rule. Comments that will be most useful and likely to influence our decisions are those that are supported by data or peer-reviewed studies and those that include citations to, and analyses of, applicable laws and regulations. Please make your comments as specific as possible and explain the basis for them. In addition, please include sufficient information with your comments to allow us to authenticate any scientific or commercial data you reference or provide.

Submitting Comments

To allow the Service adequate time to consider your comments on this proposed rule, we must receive your comments on or before March 12, 2018. We must receive requests for public hearings in writing by Feb 26, 2018.

You may submit comments on this proposed rule and draft post-delisting monitoring plan by one of the following methods:

  1. Electronically: Go to the Federal eRulemaking Portal: In the Search box, enter the Docket Number for this proposed rule, which is FWS–R4–ES–2017-0082. You may submit a comment by clicking on “Comment now!” Please ensure that you have found the correct rulemaking before submitting your comment.
  2. By hard copy: By U.S. mail or hand-delivery: Public Comments Processing, Attn: Docket No. FWS–R4–ES–2017-0082; U.S. Fish and Wildlife Service Headquarters, MS BPHC, 5275 Leesburg Pike, Falls Church, VA 22041–3803.

We request that you send comments only by the methods described above. We will post all comments on This generally means that we will post any personal information you provide us (see Public Comments section below for more information).

Document availability: A copy of the draft post-delisting monitoring plan can be viewed at under Docket No. FWS–R4–ES–2017-0082, or at the Caribbean Ecological Services Field Office web site.

Spanish language version

Read the press release in Spanish.

Post-delisting monitoring plan

Download the post-delisting monitoring plan.


Phil Kloer, Public Affairs Specialist, (404) 679-7299

The mission of the U.S. Fish and Wildlife Service is working with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people. For more information on our work and the people who can make it happen, visit Connect with the Service on Facebook, follow our tweets, watch the YouTube Channel and download photos from Flickr.

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