They are a common venomous snake renowned for the rattles on their tails, which alert nearby animals of their presence and agitation. They are found throughout the American West. Their natural habitat ranges from hot arid plains to cool mountain outcrops. Per Rockstar's poster (see image gallery, below), they can range from 3' 5" to 8' in length and weigh up to 20 pounds.
In Red Dead Redemption, rattlesnakes can be hunted and skinned for snake skin that can later be sold to merchants for cash. In-game, they are very deadly. One bite will temporarily stagger the player, a second bite will bring their health dangerously low and can sometimes be fatal, and a third bite is generally fatal.
Rattlesnakes often blend in with their surroundings and can be difficult to spot. If the player is on horseback near a rattlesnake, the horse will quickly pull up and whinny, giving the player some warning.
When approached on foot, rattlesnakes will start making hissing or rattling noises until the threat backs away. This can be used to effectively track one down and kill it.
In the Great Plains region along the cliffs. Where there is a gap leading down to the river, snakes spawn on both sides of this gap, go left along the cliffs and go around the tree and back to the gap to find more snakes. The player may have luck around camps too, up to three may spawn near them.
They can be found all around Warthington Ranch. There is a group of six rocks north-east of the building to the east in the ranch. Around this group, there are a few snakes spawning all the time during the day.
They are also found actively spawning in Mexico, by the road right above the Diez Coronas logo on the map.
Snakes spawn frequently during all hours on the cliff top just south of Escalera.
The black and yellow variants can be found hiding in bushes near Ojo Del Diablo. If you can't spot any (and this applies for multiple locations), fire a few shotgun rounds into the bushes; the wide spread will guarantee kills if there are any snakes there.
Multiple snakes spawn in small numbers in the bushes east of Coot's Chapel.
Spawning at random, small numbers of snakes can be found between the far southern border (along the cliff wall) of Sidewinder Gulch and Plata Grande.
Around Pleasance House. You will be able to find them near the house. Once you find one, go back to the cabin and sleep. When you wake up there will be another either in exactly the same place or somewhere near there. Repeat as many times as needed.
Rattlesnakes are often found in gang hideouts. Pike's Basin has lots of them (for best results, look around a campsite and corral in the eastern part of the canyon). They also spawn frequently inside Fort Mercer. I also went to Twin Rocks, cleared it, and afterwards killed around 10 of them. It is unknown if this is intentional or a glitch.
A rattlesnake spawns near the center of the abandoned wagon circle at Hamlin's Passing. Once it is killed the player can run about two seconds in any direction away from the circle and return to cause a respawn. Watch out there is also a Cougar respawn point there.
The game's soundtrack includes an atmospheric rattlesnake sound which does not indicate the presence of a rattlesnake. It is important to learn the difference between this and the actual rattlesnake sound while travelling; a real snake's sound will increase and decrease in volume as the player moves around relative to the snake's location, while the atmospheric sound simply happens at a fixed volume and then stops.
Although Rattlesnakes are found in the northern territories, in Red Dead Redemption, they keep their brown and tan coloration. Their real life counterparts are almost all black in the colder territories to absorb more heat from sunlight.
Due to their small size compared to the rest of the animals and world, rattlesnakes don't need detailed animations and modeling. Therefore, rattlesnakes in the game appear slightly boxy when zoomed in on, and their animations are very simple.
Though the game states the snakes are venomous, there is no mechanic to simulate poison or continuing damage; snakes simply deal normal damage.
While rattlesnakes are more common during the day, they will still be found in some areas at night.
The player can push a snake into a town and it will kill people as they walk by, however the snakes can be killed by lawmen.