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November 29, 2012
Robert Reed 970-420-3044 reedr@usgs.gov
Hannah Hamilton 703-648-4356 hhamilton@usgs.gov

Invasive Boa Constrictor Thriving on Puerto Rico

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MAYAGÜEZ, Puerto Rico— Non-native boa constrictors, which can exceed 10 feet and 75 pounds, have established a breeding population in Puerto Rico, one that appears to be spreading, according to research published in the journal Biological Invasions.

While boa constrictors and two species of pythons have established invasive populations in Florida, this research is the first to document a large constrictor species established in the United States or its territories outside of Florida. The new population appears to be spreading from its likely point of origin in the western part of the island around the city of Mayagüez. In the last year alone, more than 150 boas have been found in the wild on the island.

The established boa constrictor population likely originated with the pet trade. Genetic studies conducted by the researchers indicate that individual boas on the island are highly related and that the population probably originated with a small number of snakes. First-hand accounts from local officials suggest that newborn boas were released in Mayagüez in the early 1990s.

"Experience has shown that island ecosystems are particularly vulnerable to snake invasions, and unfortunately Puerto Rico has no natural predators that can keep the numbers of these prolific, snakes in check," said USGS Director Marcia McNutt. "Humans were responsible for introducing this scourge to the island, and are the only hope for mitigating the problem before it is too late for the native species."

Two snakes found some distance from the expanding Mayagüez population share genetic markers with that population, suggesting that people might be intentionally or unintentionally moving the snakes around the island. Such movement could potentially increase the rate of spread of this invasive snake. Because the snakes are secretive and difficult to spot, the researchers suspect the population size is large.

“We’ve learned from dealing with other invasive snakes that understanding the source of these populations and preventing spread as soon as possible is important to protect ecosystems," said USGS scientist and study co-author Bob Reed. "Once non-native snakes become established across a large area, especially in densely forested areas, they become much more difficult to find and almost impossible to eradicate."

Private ownership of boa constrictors and most other snake species is prohibited in Puerto Rico because of fears of non-native snakes becoming established.

The paper, "Genetic Analysis of a Novel Invasion of Puerto Rico by an Exotic Constricting Snake," was authored by R.G. Reynolds, University of Massachusetts, Boston; A.R. Puente-Rolón, Universidad Interamericana de Puerto Rico, R.N. Reed, U.S. Geological Survey; and L.J. Revell, University of Massachusetts, Boston.


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