How do cats squeeze through small spaces?

Cats are so flexible that a 2014 study half-jokingly investigated whether felines are liquids. But joking aside, traditional fluid mechanics can't explain kitties' impressive contortions when squeezing through small holes. So how do cats pull off these feats?

The key to cats' ability to apparently "flow" like fluids through tiny gaps is their unique shoulder girdle. In humans, the shoulder girdle is composed of the shoulder blades, or scapulas; and the collarbones, or clavicles, according to the National Center for BioTechnology Information (NCBI).

The shoulder blades and the collarbones are connected together in humans. The resulting shoulder girdle provides rigid support for the muscles of the arms, the NCBI noted.

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In contrast, the shoulder blades of cats are attached to the rest of the body only by muscles and not bone, according to the Catonsville Cat Clinic in Maryland. The same holds true for cats' collarbones, Nathalie Dowgray, head of the International Society of Feline Medicine in the United Kingdom, told Live Science. Moreover, feline collarbones are much smaller in comparison with the rest of the cat's body than human collarbones are to the rest of our bodies, Dowgray said.

These anatomical features help cats squeeze through tight openings. "Being able to fit into small spaces is an evolutionary advantage when hunting small prey such as mice, but also for hiding and escape from potential predators," Dowgray said.

In addition, cats' whiskers also help them squeeze through spaces. Whiskers are hairs that are twice as thick as cats' "guard hairs" (the longer, coarser hairs in cats' fur) and sit three times as deep within the skin, Dowgray said.