Unlike leaves and twigs, snakes have smooth, curved bodies. Scan the image for any arcs or curves that pop against the angular backdrop.
Rattlesnakes usually have patterns of brown, tan, and black scales. These might stand out a smidge against the leaves, even if the colors are similar.
Look for small glints of light on the snake’s scales. These flashes can sometimes give its location away.
The snake’s texture might be a tad different from the leaves. While leaves are mostly flat, the snake’s body has a 3D feel.