If you're trying to mimic the snake effect, why not mimic the materials used by the snake? Cylinders of lightweight wood, such as pine, balsa, or basswood. With a strip of leather or rubber running up the core. Each cylinder is adhered to the strip directly, with a little space between each, This lets the body flex, instead of them all stacking up together at the bottom.
The snakes use a rather thick strip so that it only flexes in 1 dimension. I expect, if making a cat tail, you'd want a thinner strip, so that it flexes more readily in 2 dimensions. But it's up to you. Do small-scale tests to see what you like.
If the result is too heavy, you can lighten it by drilling holes parallel to the strip through each cylinder.