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Animal Fact Sheets


Aruba Island rattlesnake range map


(Crotalus unicolor)

Classification and Range

The Aruba Island rattlesnake belongs to the family of vipers, Viperidae. Pit vipers together form the subfamily Crotalinae. The "pit" vipers are so-called because they have heat-sensing pits behind and below their nares (nostrils). Besides rattlesnakes, some other kinds of pit vipers are water moccasins (also known as cottonmouths), copperheads, palm vipers and bushmasters. The Aruba Island rattlesnake (C. d. unicolor) is a subspecies of the Neotropical rattlesnake (C. durissus), which ranges from Mexico to Argentina.


Aruba Island rattlesnakes (hereafter simply referred as "Arubas") are only found on the desert island of Aruba, located off the coast of Venezuela. The total amount of habitat for the snakes is only 12 square miles (31 sq km) of the island's dry interior; vegetation there is very sparse.

Physical Characteristics

Aruba Island rattlesnakes (hereafter simply referred as "Arubas") are only found on the desert island of Aruba, located off the coast of Venezuela. The total amount of habitat for the snakes is only 12 square miles (31 sq km) of the island's dry interior; vegetation there is very sparse.

Length and Weight

The maximum size for Arubas is 37 inches (94 cm). A typical adult specimen weighs 2-3 pounds (0.9-1.4 kg). Males tend to be larger than females.

Life Span

12-25 years (estimated).


In the wild:Probably rodents, lizards and birds At the zoo: Mice of a size appropriate to the age and size of the snake.


Arubas become sexually mature at about 3 years of age. A male rattlesnake uses the courtship moves common to many kinds of snakes. First, the male aligns its body along the upper (dorsal) surface of a pheromonally attractive female. Next, the male rubs its chin along the female's back, moving his entire body along hers in a jerky fashion that demonstrates interest. Then, If the female is receptive, she opens her cloaca, and lets the male insert one of a pair of copulatory organs, called hemipenes. Rattlesnakes may mate for several hours at a time. About four months after mating, the female gives live birth to a litter of five to seven babies, although one Woodland Park Zoo Aruba produced a litter of 12.

Life Cycle

Newborn Arubas are only a few inches long and weigh about half an ounce (14 g). Young snakes are independent from birth. A few days after they birth, the young shed their skins for the the first time and begin looking for food. During their first year of life, young Arubas can grow to 6-9 inches (15-23 cm) in length.

Death by Lethal Injection

Like other rattlesnakes, Arubas inject their prey with a lethal cocktail of enzymes and other complex chemicals that both kill the animal and actually begin to digest it from the inside out. Long-hinged fangs, which are usually folded back so that the mouth can be closed, swing forward as the snake strikes out at its prey. In spite of darkness, the snake may locate and identify its prey by using its heat-sensing pits. The snake then swallows its prey whole, as other snakes do. A snake swallows its prey whole by unhinging its jaw at the pivots (if necessary) and allowing the flexible lower jaw (called the symphysis) to stretch enough so the snake can engulf its dinner. In the wild, an adult Aruba might only eat a few times a year, and a well-fed specimen could probably go for a year or more without food.

Location at the Zoo

The Day Exhibit contains the Aruba Island rattlesnake display. The snake on exhibit is one of two females which together have given birth to 40 babies, as part of the Species Survival Plan's goal of maintaining a self-sustaining zoo population. Other species of venomous reptiles on exhibit in the Day Exhibits include the King cobra, Northern Pacific rattlesnake, western diamondback rattlesnake, eyelash viper and Gila monster. None of the venomous reptiles at Woodland Park Zoo have been surgically altered to make them less dangerous. The last incident of a venomous reptile bite at Woodland Park Zoo occured in the 1930s. The keeper at that time, the late Frank Vincenzi, (who later became WPZ's director) was bitten by a Northern Pacific rattlesnake.

Conservation Connection

Aruba Island rattlesnakes are listed as critically endangerd. These snakes live in vulnerable habitat and over such a tiny area. Fortunately, the government and people of Aruba understand the importance and value of their own special kind of rattlesnake, and have set aside a large portion of the interior of their island as protected habitat for this rattlesnake and other wildlife. Woodland Park Zoo participates in the American Zoo and Aquarium Association's (AZA) Species Survival Plan (SSP) for the Aruba Island rattlesnake, by helping to maintain the captive population's numbers and genetic health, and by contributing to efforts to study and protect the Aruba in its native habitat.

One such study is the Aruba Island Rattlesnake program that informs local people about the plight of endangered snakes. The westernmost Caribbean island of Aruba is part of the Netherlands Antilles in South America; it is about 18 miles (29 km) off the coast of Venezuela. Aruba covers an area of just 70 square miles (181 square km). Approximately 81,000 people live there year-round, but more than 540,000 tourists visit annually.

As with snakes in many other parts of the world, inhabitatns of and visitors to Aruba regard snakes as a "nuisance." Although this is far from the truth, neither locals nor tourists want snakes near homes or businesses. Their fears lead to the killing of many unwanted snakes. As wildlife officials have become aware of the dangers facing these snakes, the officials have changed their method of dealing with snakes in or near areas of human usage. Instead of exterminating the snakes, officials now translocate them. Unfortunately, previous field studies suggested a significant increase in mortality for translocated snakes. This program uses radio telemetry to study translocation effects on rattlesnake survival and its newly acquired habitat. If translocation decreases the survival rate of the snakes, this project will investigate other options.

Other options may include "halfway houses" or shorter transport distances. In addition to field research, project personnel present education programs for schools or other groups and began a public relations campaign to highlight Aruba's endangered species. As a result, success stories and research information discovered in these types of conservation projects can help other species of "nuisance" reptiles. Each in-situ projected supported by the zoo aims to provied a broad, holistic approach to conservation, encompassing research, education, habitat and species preservation. These projects include comprehensive and cooperative strategies to link the needs of animals with the people who share their ecosystems.

How You Can Help!

The effort to save threatened species like the Aruba requires cooperation and support at the international, national, regional and individual levels. You can help in this cause. Protect rattlesnakes everywhere by refusing to persecute them, and by encouraging other people to respect them as well. Join and become active in Woodland Park Zoo and other conservation organizations of your choice. Let your elected representatives know your views about protecting endangered species and wild habitats. Contact Woodland Park Zoo at to find out other ways you can support conservation programs at the zoo.

Discover more about snakes by contacting the Society for the Study of Amphibians and Reptiles at: 303 W. 39th St., PO Box 626, Hays, KS 67601; or the American Federation of Herpetoculture at: AFH, P.O. Box 300067, Escondido, CA, 92030-0067. Learn other ways you can help conserve wildlife and the habitats they require for survival by visiting our How You Can Help page.

Reptiles as Pets

We do not recommend reptiles as pets for most people as they require very specialized diets and environments. We also receive hundreds of requests each year to take former pet iguanas, boas and other reptiles but we cannot accept these due to space, health and unknown backgrounds. If you need to find a reptile or amphibian a new home, we suggest you contact a local herpetological group in your area.

In the Puget Sound region, contact the Pacific Northwest Herpetological Society as a resource. If you do choose to get a reptile as a pet, please learn as much as possible about their care and the best species before making your decision and never accept wild-caught animals as pets or release non-native reptiles or amphibians into the wild.

Sources and Suggested Reading

Klauber, Lawrence. 1956. Rattlesnakes. University of California Press, Berkeley, CA. 2 vol., 1536 p.

Mehrtens, John M. 1987. Living Snakes of the World. Sterling, New York, NY. 480 p.

Phelps, Tony. 1981. Poisonous Snakes. Blanford Press, Poole, Dorset, UK. 237 p.

For Kids!

Markle, Sandra. 1995. Outside and Inside Snakes. MacMillian Books, New York, NY. 40 p.

Resmick, Jane P. 1996. Eyes on Nature: Snakes. Kidsbooks, Inc., Chicago, IL. 29 p.

Zoobooks. 1992. Snakes. Wildlife Education, Ltd., San Diego, CA. 16 p.

Aruba Rattlesnake Taxonomy

Phylum: Chordata
Genus: Crotalus
Species:C. durissus unicolorv

Aruba Rattlesnake Fascinating Facts

  • All rattlesnakes (and nearly all pit vipers) give birth to their babies alive rather than laying eggs!
  • Baby rattlesnakes can deliver a painful bite the day they are born!
  • A mouse bitten by an Aruba rattlesnake dies in less than one minute!
  • Rattlesnakes probably evolved their rattle in North America, where there are the most kinds of rattlers, as a way of warning large hoofed animals not to step on them. Large migrating herds of bison made having a rattle a really useful feature for prairie-dwelling snakes!