Bio Facts: Rattlesnake, Aruba Island
Aruba Island Rattlesnake
Crotalus durissus unicolor
Indigenous to Aruba Island located in the Caribbean off the coast of Venezuela.
Rocky hillsides and adjacent rocky, sandy fields (habitat dominated by desert flora).
This is a small to medium-sized, light gray, gray-brown, or peach-colored snake. It has overlapping dorsal scales that are a pale brown in color and triangular in shape. The head and neck may have a pair of stripes that extend well onto the body. Adults reach a length of approximately 3 feet (95 cm) and weigh between 2 to 3 lbs. (0.9 to 1.4 kg). Males tend to be larger than females.
12 to 20 years
About 3 years
In the wild, rodents, small lizards, frogs, mammals and birds; at the Zoo, a variety of rodents.
US – Threatened; IUCN – CR (Critically Endangered); SSP
Nocturnal during the warmer months, active in early morning and late afternoon during the rest of the year. In the wild, it probably preys on rodents, lizards and birds mostly. After killing its prey with a venomous bite, like other snakes, it swallows its prey whole by unhinging its jaw at the pivots and allowing the flexible symphysis at the front of the mandible to stretch enough so the snake can engulf its dinner. In the wild, an adult may only eat a few times each year, and a well fed adult could probably go for a year or more without food.
The mating season on Aruba lasts from September to January. Aruba Island rattlesnakes are live bearing rather than egg laying. After a four-month gestation, five to twelve young are born. Newborns are only a few inches long and weigh about half an ounce (14 g). Independent and venomous from birth, they start searching for their first meal after they shed for the first time. During their first year, young may grow to two to three times their length at birth.
A male uses the courtship moves common to many kinds of snakes. He aligns his body along the dorsal (back) surface of the phermonally attractive female, rubs his chin along her back, flicking his tongue and moving his whole body along the length of hers in a jerky motion that demonstrates his interest. If she is receptive, she raises her tail and lets him insert one of his paired copulatory organs (hemipenes). They may mate for several hours at a time.
They have heat-sensing pits used to locate prey. The rattle is used for defense, warning off potential predators. The venom is a lethal combination of enzymes and other chemicals that both kill prey and begin to digest it. Long-hinged fangs fold back when the mouth is closed and swing forward when the snake strikes. A mouse bitten by an Aruba Island rattlesnake dies in less than a minute. Aruba Island rattlesnake venom is among the most toxic of any rattlesnake.
The Aruba Island rattlesnake, also called the Arubian cascabel, is one of the rarest rattlesnakes in the world.
Only twelve square miles of relatively undisturbed habitat remain on Aruba. Resort development and other forms of human encroachment are the biggest threat to the rattlesnake. In past centuries, much of the island’s trees were cut down for charcoal and firewood, and some land was used for aloe cultivation. Introduced feral goats have wreaked havoc on the vegetation, even at the southern end of the island. There are also some concerns about the number of snakes being captured for pets or killed for their rattles. While export of the snake from the island is illegal, it has no other legal protection.
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.
A crested rattlesnake is often depicted with a masked shaman on Mexican pottery and figurines. It is a totem animal for certain Amerindian tribes.
The Aruba government recognizes the uniqueness of the country’ s endemic rattlesnake and has featured it on several Aruba Island postage stamps and even on new currency.
The cunucu land area has long been a candidate for becoming a national park on Aruba. The AZA Aruba Island Rattlesnake SSP had proposed that a national park would protect several other native Aruba species along with the rattlesnake. In 1997, the Aruba government established Arikok National Park, which encompasses about 19% of Aruba’s total landmass and most of the current range of the rattlesnake. Plans are underway to correct the feral goat problem and possibly seek to list the rattlesnake on the CITES Appendix II. A recently completed field study supported by the AZA and the Aruba Department of Agriculture should shed new light on the snake’s current wild population and its natural history. Radio transmitters implanted in four snakes provided much information about home ranges, courtship and mating, and travel activity.
Education has been a vital component of the SSP’s conservation programs on Aruba. Media campaigns geared toward adults and educational programs for children have focused on Aruba’s unique ecosystems emphasizing the role of the rattlesnake. Radio and television interviews, magazine and newspaper articles, teacher workshops, and Environmental Education workshops have all served to increase awareness of the snake and to create a better public image among local people.
Currently there are ~150 snakes managed under the AZA’s SSP (Species Survival Plan). The Aruba Island government presented the SSP program with a gift of ten wild-caught snakes for the breeding program. One area of concern is Paramyxovirus, which has killed several captive snakes. A vaccine for the virus has been tested on several animals surplus to the breeding program. Additional vaccine trials are planned for the future. Other areas of research are artificial insemination in these snakes, determining whether female snakes can retain sperm from one season to the next (which could confuse parentage and thus studbook records), and determining whether “soft releases” of captive or nuisance snakes prior to release onto Aruba increases survivorship.
Jacksonville Zoo History: