The Marajoan rattlesnake is an isolated subspecies, unique to the microregion of Marajo (Ilha de Marajó), a large island in the Amazon Delta. Little is known about its life history or ecology. It is known to use open fields and savannas on the island. It is believed to feed primarily on mammals, though anecdotal reports indicate it may also take birds, lizards and other snakes on occasion.

Its venom, like that of other Crotalus durissus subspecies, is reported to be primarily neurotoxic, with some myotoxic effects.

A visually distinct feature of this subspecies is that it lacks the classic neck stripes associated with most other Neotropical & South American rattlesnakes, instead it has a number of scattered black scales dotting the side of its neck.