Black-tailed rattlesnakes often have faint light bands on their tails, which can be confusing to observers who believe that they can only be solid black. On this one, it’s just barely visible, appearing as black and dark grey bands in a ratio similar to a Western Diamondback Rattlesnake. These are not hybrids, as is often suggested by people online. A more accurate way of viewing an all-black tail from this species: a banded tail with variable lighter bands, which often darken to be indistinguishable from the darker ones.
The rattle on this snake is also complete, which includes the full button that the snake was born with. The small, last segment, shows the rounded tip (prebutton), and notch that it gained with that first shed skin. This creates a full button, which it may rattle without making any sound. The subsequent sections (not “buttons,” as they are often mistakenly called) are left with each shed skin, which a young snake may do several times in a year. The shape of the rattle, too, indicates its age here. The strong taper, with each segment being larger than the previous, says that this snake is growing quickly. Once growth slows and nearly stops, each segment will be similar or identical in size to the previous, indicating an older snake.
This one was found near Phoenix a few years back.
