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The Natural History of the World’s Rarest Viper, the Aruba Island Rattlesnake

Occasionally I like to highlight animals that, while not suitable as pets, are none-the-less of great interest to reptile enthusiasts.  The Aruba Island Rattlesnake, Crotalus unicolor, native to a place known more for its resorts than for reptiles, is one such beast…from diet to range to appearance, it is most unique.

Please Note: I’ve had the good fortune of working with Aruba Island Rattlesnakes at the Bronx and Staten Island Zoos.  This came about in connection with a lifetime of training and experience, supported by an emergency response team that would assure rapid care in the event of a bite.  I would not keep venomous snakes in my private collection, nor should anyone.


Despite the “plain-sounding” species name (unicolor), the Aruba Island Rattlesnake is a beautiful animal.  Individuals vary greatly, and may be pale-gray, pinkish-gray or gray-brown in color, with pale-brown rhomboid markings down the back.  Their subtle hues match the rocky habitats they frequent.  The stoutly-built adults typically average 24-30 inches in length, but occasionally reach 3 feet.

The Aruba Island Rattlesnake was once considered to be a subspecies of the Neo-tropical Rattlesnake, Crotalus durissus.


Aruba RattlesnakeThis species is limited to the southern tip of Aruba Island (Netherlands Antilles), 15 miles off the coast of Venezuela.  Its entire range covers a mere 10 square miles.


The Aruba Island Rattlesnake is found only in those few areas of the island that are largely inhospitable to people.  It frequents rocky hillsides, arroyos and adjacent rock-sand fields, among cactus and thorn-scrub.


Found only within 10 square miles of an already tiny natural range, this snake is threatened by resort development, habitat destruction (largely due to the activities of feral goats), and, at least in the recent past, collection for the pet trade.

It is protected by the government of Aruba, designated as “Threatened” by the US Fish and Wildlife Service, “Critically Endangered” by the IUCN and listed on Appendix II of CITES.

The Aruba Island Rattlesnake breeds well in captivity and is currently the subject of a zoo-based Species Survival Plan, field studies and an education program onAruba.  It has recently been featured on the island’s postage stamps and currency.  Eradication of feral goats, to preserve remaining habitat fragments, is being considered.

Conservation efforts are hampered by the fact that the snake is venomous and its range has long been heavily utilized by people.


Captive longevity approaches 20 years; unknown in the wild.


Mating occurs from September through January.  The young, 2-9 in number, are born alive after a gestation period of approximately 240 days.  They average 8-11 inches in length and feed primarily upon lizards and frogs.


Rats, mice, lizards, frogs, birds and, possibly, bats.

It is interesting to note thatArubahas no native terrestrial mammals other than bats.  In contrast to other large rattlesnakes, this species must have subsisted largely upon reptiles, birds and amphibians prior to the introduction, by people, of Norway Rats and House Mice.

Other Rattlesnakes

The following information is taken from an article I wrote on the Natural History of Rattlesnakes. Please see the original article to learn more about these fascinating creatures.

Neotropical RattlesnakeRattlesnakes and their relatives, collectively known as “pit vipers”, are classified in the subfamily Crotalinae, along with palm vipers, copperheads, cottonmouths and related species.  They are considered to be the most advanced, or highly evolved, of the snakes.  All possess a sophisticated organ that detects the infra-red rays (heat) produced by birds and mammals.

Rattlesnakes are confined to the Western Hemisphere, and reach their greatest diversity in the American Southwest and Mexico.  Thirteen of the 33 known species are found in Arizona alone.  Only 4 species range east of the Mississippi (Eastern Diamondback, Eastern Massasauga, Pigmy Rattlesnake, Timber Rattlesnake) while South America is home to but 2 species (Neo-tropical Rattlesnake, Uracoan Rattlesnake).

The rattle, unique among snakes, is composed of a series of loosely-connected segments.  Specialized muscles in the tail vibrate the rattle to produce the characteristic warning sound.

All rattlesnakes bear live young and some species appear to provide a degree of parental care to their offspring.  The Black-tailed Rattlesnake has been shown to recognize siblings after a 2 year separation.

Rattlesnakes and other vipers have evolved long, hinged fangs that fold back against the roof of the mouth when not in use.  Venom is injected with a single bite, in the manner of a hypodermic needle.



Further Reading

American Zoo Association Studbook (inventory of captives) and conservation strategy

Video: ArubaIs Rattlesnakes courting

Aruba Island Rattlesnake videos, photos and facts

Aruba Island Rattlesnake image referenced from wikipedia and originally posted by Ben Lunsford
Neoptropical Rattlesnake image referenced from wikipedia and originally posted by LtShears

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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