The Aruba Island rattlesnake, or Crotalus unicolor, is a critically endangered rattlesnake that is endemic to the Caribbean island of Aruba, located just off the coast of Venezuela. The snakes usually have a uniform gray or light brown body color, although they sometimes have diamond-shaped markingson their backs. The snake is nocturnal during the hot summer months but will venture out during the cooler early-morning and late-afternoon periods.

The rattlesnake is viviparous, which means that it gives birth to live young rather than laying eggs. It has an estimated lifespan of up to 20 years, and its diet is made up of mainly rodents, birds, and lizards. It is estimated that there are only 230 surviving adults in the wild, with about 100 more adults in captivity. This snake is, unfortunately, threatened by encroaching human development—it only has about 25 square kilometers (9.5 mi²) of undeveloped habitat in which it survives. The introduction of goats has also had a negative impact on the vegetation of the island, reducing these snakes’ habitat even further.