Aruba Island rattlesnake

Scientific name: Crotalus unicolor

Country: Aruba Island, off the coast of Venezuela

Continent: South America

Diet: Carnivore

Food & feeding: Small rodents, birds and lizards

Habitats: Rocky, dry covered with cactus scrub and thorny plants

Conservation status: Critically endangered

Relatives: Adder (Vipera berus), eastern diamond-backed rattlesnake (Crotalus adamanteus)

Description: Its short, stocky body is brown with a lighter brown tail tip.  The scales have distinctive pink, blue and brown diamond-shaped markings. Individuals are on average one metre long.  Males and females are similar in appearance though males are slightly larger. The tail creates the rattling noise that gives this snake its name. This species belongs to the family of vipers, so like other vipers it has a V-shaped head. It has long, venomous, hollow fangs which fold against the roof of the mouth when they are not being used.

Lifestyle: This snake is active in the early morning and late afternoon, however is forced to be nocturnal in the hotter months. Its expected lifespan in captivity and in the wild is between 12 and 20 years.

Family & friends: These snakes are solitary so rarely come into contact with members of the same species.  However, males may compete for females during the breeding season.  There is no parental care as the young are independent from birth.

Keeping in touch: The rattle on the end of the tail is used to communicate with other species.  It is made from a series of hollow keratin structures. When these are vibrated using fast muscles, they make a characteristic sound to warn predators.

Rattlesnakes possess a pair of pit organs located below the nostrils. These organs contain infrared receptors that provide information about the body heat of an animal near to them.  This information also gives details on distance, size, and shape of close animals. These allow the snakes to hunt during low light and night-time conditions. This method is more effective in detecting warm-blooded prey than cold-blooded prey.  Sight is still used in conjunction with infrared sensory detection. 

Pheromones are an important form of communication. These rattlesnakes can pick up odours using both the sense of smell and the Jacobson’s organ which is found on the roof of the mouth. Aruba Island rattlesnakes have a highly developed sense of smell, as do most snakes.

Growing up: Fertilization in Aruba Island rattlesnakes is internal and the breeding season occurs from September to January. Mated females give birth to 5 -15 live young after four months of gestation. The young have fully functional venom sacs at this time and average 20 cm in length and 14 g in weight. After their first slough (skin shed), the young begin to hunt for their first meal. They may double or triple in size in the first year. At four years for males and five years for females, they are ready to breed.

Conservation news: Habitat destruction occurs in Aruba in the form of charcoal and firewood industry, aloe cultivation, and tourism development. This has reduced the habitat available for Aruba Island rattlesnakes to only twelve square miles. Even in this small area, there is a growing feral goat population that is destroying native vegetation. The problem has begun to be addressed with growing support for the preservation of the island's endemic species. Media campaigns and education programs are highlighting the ecological and economic importance of this native rattlesnake. An improved public image has emerged from articles, interviews, and educational efforts, resulting in the Aruba Island rattlesnake being featured on new currency and postage stamps. Conservation posters are being developed by the American Association of Zoos and Aquariums (AZA) to further promote these efforts.

Along with this growing respect for the snakes, the AZA Aruba Island Rattlesnake Species Survival Plan (SSP) helped establish the Arikok National Park. The park consists of 19% of Aruba’s land and includes most of the rattlesnake population. There are also plans underway to remove feral goats and list the species in CITES, Appendix II, to ban trade of the snakes into the pet trade and sales of the rattles.

There are currently about 230 rattlesnakes left in the wild and about 110 managed by the AZA (53 females and 57 males) in zoos.