Circular Reasoning

A snake appears content to slither
unlike the dolphin and the whale,
though if you bother asking either
the tale is rather of the tail:
for cetaceans, an appendage
and thus a portion, a percentage
of the entire body’s length,
although the source of all its strength.
But for the snake? A harder question:
Where does snake end, and tail begin?
Without a rattle or a fin,
it’s hard to know, but a suggestion
to help the skeptic get it right:
start from the end that doesn’t bite.

Author notes: image by author prompt to GPT