At seven feet long, Puerto Rican boas—also known as yellow tree boas—are the largest snakes on the island of Puerto Rico. They’re relatively slender reptiles with a dull brown or gray coloration and dark blotches along their bodies. These snakes are not venomous. Instead of using venom to immobilize prey, the boas are constrictors that use their bodies to wrap around prey until it suffocates.
Although they can swim and slither over the ground, Puerto Rican boas are primarily arboreal, meaning they frequently spend time in trees. They’re found in greatest numbers in the northwestern karst region of Puerto Rico. Karst landscapes are dominated by rock that dissolves easily in water, which leads to the formation of caves and sinkholes. The boas are also found in rain forests and even plantations.
Despite the Puerto Rican boa’s intimidating status as a constricting carnivore, it’s not at the top of the food chain. Mongooses—catlike mammals native to Africa and Asia—frequently make a meal of the boa. Mongooses were originally brought to Puerto Rico to keep down pest rodent populations, but they ended up attacking a number of beneficial wildlife as well.
Puerto Rican boas eat birds, lizards, rodents, and bats. To capture quick-flying bats, the boas have developed a clever hunting technique. They curl their tail around a tree branch and hang patiently in front of a cave opening. When bats fly out en masse at dusk, the boa has numerous chances to catch a bat right out of the air. Puerto Rican boas don’t have venom, nor do they need it. After they’ve captured their prey, they use their powerful muscles to squeeze the unlucky animal to death, and then they swallow it whole.
Puerto Rican boas mate in springtime at the beginning of the wet season. They are viviparous, which means the females give birth to live young rather than lay eggs. When the offspring are born, they are able to fend for themselves and don’t receive any extra care from their parents. The lifespan of wild Puerto Rican boas is unknown, but they can live up to 20 years in captivity.
Puerto Rican boas are federally listed as endangered. Mongoose predation and harvest by humans for folk remedies have probably led to their decline, but they may not be as rare as once thought. It’s hard to spot them in the trees, which may have led to low counts, but they’re actually common in some regions.
The Puerto Rican boa has a place named for it. The Cave of the Boas, which houses several hundred thousand bats, is prime hunting territory for these snakes.
The IUCN Red List of Threatened Species
Utah’s Hogle Zoo
U.S. Fish & Wildlife Service
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