* Lowest body mass: If so, the ethereal mole (Neurotrichus gibbsii) is a strong contender, weighing a mere 5-10 grams.
* Longest and thinnest body: The lesser long-nosed bandicoot (Perameles bougainville) is incredibly slender with a long, thin body.
* Smallest circumference: The bumblebee bat (Craseonycteris thonglongyai) has a body size of only about 29 millimeters (1.1 inches), making it the smallest mammal in the world and likely having a very small circumference.
Ultimately, there's no single definitive answer to what the "skinniest" mammal is. It depends on what metric you're using to measure "skinny."