Cork or rubber handles?
I've had mice eat my cork fly rod handles for years if they weren't in a case. Mice and rats will also eat black rubber for whatever reason. A rat once worked it's way into my car through the air conditioning filter and chewed completely through several black wires. Only black wires, metal and all. Guess he liked licorice. Maybe had a copper deficiency too.
Sweat, salt, and whatever food you touched with your hands before hiking with your poles attracted your critter.