The El Muerto Island rattlesnake is very small, staying under 2 feet long as mature adults. They occur on El Muerto Island in the Sea of Cortez off of Baja California. The island is quite small, and the habitat is rocky and very hilly with some inaccessible areas. Crotalus muertensis is well-adapted to the rocky hillsides and arid conditions of this island.

Introduced feral cats likely play a negative role on this species presence on the island--if not through direct confrontation, then presumably through competition for native prey.

This species exhibits insular dwarfism, a phenomenon resulting in a significant decrease in size from their nearest relatives. Dwarfism correlates with small island size, competition among its own species, and abundance of smaller prey items.