Proposed Removal of Puerto Rican Boa From The List of Endangered and Threatened Wildlife - Questions and Answers

1) What is a Puerto Rican boa? 

The Puerto Rican boa, a large nonvenomous snake native to Puerto Rico, is widely distributed across the island but not uniformly abundant. A nocturnal, tree-loving snake, the Puerto Rican boa is considered a habitat generalist and tolerates a wide variety of habitat types from coastal forests to wet karst and montane forests, along streams, forest and road edges, and within rural, suburban and some urban areas. Cave systems are particularly important for this species because they provide prey and shelter. They generally feed on rats, mice, bats, lizards, and birds.    

2) What action is the U.S. Fish and Wildlife Service (Service) proposing to take? 

The Service is proposing to remove the Puerto Rican boa from the Federal List of Endangered and Threatened Wildlife. This proposed action is based on the best available scientific and commercial data which indicates that the species has recovered and no longer meets the definition of an endangered or threatened species under the Endangered Species Act (ESA).  

3) Why was the Puerto Rican boa listed under the ESA? 

The Puerto Rican boa was originally listed as an endangered species in October 1970 under the Endangered Species Conservation Act of 1969, and remained listed with the passage of the ESA in 1973 due to its decline in both population size and distribution as a result of widespread deforestation in the 1800s.  

4) How many Puerto Rican boas are there now? 

At the time of listing, there was very little information about the boa's population estimates, but it was generally considered to not be abundant. Today, Puerto Rican boas are more common and widely distributed than previously known. Using an island-wide population projection, there could be more than 30,000 Puerto Rican boas unevenly distributed across the island.   

5) Why is the U.S. Fish and Wildlife Service proposing to remove the Puerto Rican boa from the Federal List of Endangered and Threatened Wildlife? 

Under the ESA, an endangered species is defined as a species that is “in danger of extinction throughout all or a significant portion of its range.” The Service must determine whether a species meets this definition because of any of the following factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range;  (B) Overutilization for commercial, recreational, scientific, or educational purposes;  (C) Disease or predation;  (D) The inadequacy of existing regulatory mechanisms; or  (E) Other natural or manmade factors affecting its continued existence. Given a thorough review of the best available scientific and commercial information, which includes analyses of species threats and population status, the Service has determined the Puerto Rican boa no longer meets the definition of endangered or threatened under the ESA. 

6) What recovery actions were implemented to lessen the threats to the species? 

Since its listing, many Commonwealth and Federal laws have been implemented that provide protection for habitat in areas where the Puerto Rican boa is known to occur. As of 2018, approximately 16 percent of the island was designated as protected areas for conservation. The species has been documented in numerous protected areas across the island, like in El Yunque National Forest,  the Río Abajo, Guajataca, Camabalache, Vega, and Maricao Commonwealth forests managed by the Puerto Rico Department of Natural and Environmental Resources, as well as within several of the lands managed by the Puerto Rico Conservation Trust through its unit Para La Naturaleza, like El Convento Caves Natural Protected Area.  

Restoration and management of private and public lands that were historically impacted by deforestation, agriculture, and other human development activities have also helped contribute to improved habitat for the boa. These conservation efforts have increased available habitat and have positively contributed to the species current status.  

Other factors that have positively influenced the status of the Puerto Rican boa include translocation efforts and outreach and education efforts that have increased awareness of the species and changed attitudes from persecution to protection.   

7) What are the remaining threats to the Puerto Rican boa? 

The primary drivers affecting the current and future status of the Puerto Rican boa include habitat loss, degradation, and fragmentation.  These drivers also exacerbate other stressors such as road kill and increased conflicts with humans and exotic animals such as cats, as well as the need for management (e.g. translocations).  Emergent diseases, hurricanes (and post-hurricane recovery efforts), and competition with other exotic and introduced snakes may also impact Puerto Rican boa viability. 

8) How did the Service determine that the Puerto Rican boa was recovered and warranted delisting? 

After considering the best available information, the U.S. Fish and Wildlife Service has determined the Puerto Rican boa no longer meets the definition of a threatened or endangered species under the ESA.   

A 5-year review was initiated for the species in 2019 and a Species Status Assessment (SSA) report was completed in 2021.  The peer-reviewed SSA report represents a compilation of the best scientific and commercial data available concerning the status of the species and is the foundation for this proposed rule.   

The SSA report found that there is island-wide distribution of suitable habitat for the Puerto Rican boa and that the species is considered well buffered against the effects of catastrophic events.  Additionally, the species has a relatively high genetic diversity and is considered more abundant today than at the time of listing, with a potential island-wide population estimate of more than 30,000 boas.  

9) Will the status of the Puerto Rican boa continue to be monitored? 

Yes. The ESA requires the Service, in cooperation with the State, to implement a monitoring program for not less than five years for all species that have been delisted due to recovery, referred to as post-delisting monitoring (PDM). These are activities that are undertaken to verify that a species delisted due to recovery remains secure from the risk of extinction after protections of the ESA no longer apply.  If population declines are detected, the goal of the PDM plan is to take measures to halt those declines so that proposing the species as endangered or threatened is not again needed.  

10) How do I submit comments on this proposal? 

The Service will accept comments received or postmarked on or before September 12, 2022. Comments submitted electronically to the Federal eRulemaking Portal at must be received by 11:59 p.m. Eastern Time on the closing date. We must receive requests for public hearings, in writing, at the address shown in FOR FURTHER INFORMATION CONTACT by August 29, 2022. 

This proposed rule and supporting documents are available at under Docket No. FWS-R4-ES-2021-0162.  

FOR FURTHER INFORMATION CONTACT: Edwin Muñiz, Field Supervisor, U.S. Fish and Wildlife Service, Caribbean Ecological Services Field Office.  Email address:  Mailing address: P.O. Box 491, Boquerón, Puerto Rico 00622. Telephone: (787) 405-3641. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Relay Service at 800–877–8339. 

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Endangered and/or Threatened species