In 1894, the French physiologist Étienne-Jules Marey tried to resolve a particularly vexing question in science: How do cats always seem to land on their feet when they fall? Using the era’s rudimentary videos, Marey was able to definitively illustrate that cats, when dropped from a height, were able to right themselves in the air unaided.
The findings shocked the scientific community, but the mystery of how cats ultimately achieve this feat have remained unresolved.
In a paper, published last month in the journal The Anatomical Record, researchers offered a novel take on falling felines. Their evidence suggests new insights into the so-called falling cat problem, particularly that cats have a very flexible segment of their spines that allows them to correct their orientation midair.
Greg Gbur, a physicist and cat-falling expert at the University of North Carolina at Charlotte who was not involved with the paper, said the study was the first he knew of that explored “what the structure of the cat’s spine tells us about how a cat turns over while falling.” He added that the research uncovered many remarkable details about how cats maneuver while falling.
People have been curious about falling cats perhaps as long as the animals have been living with humans, but the method to their acrobatic abilities remains enigmatic. Part of the difficulty is that the anatomy of the cat has not been studied in detail, explains Yasuo Higurashi, a physiologist at Yamaguchi University in Japan and lead author of the study.
“Physicists have tried to model the behavior in relatively simple equations,” saidRuslan Belyaev, a zoologist at the Severtsov Institute of Ecology and Evolution in Moscow who was not involved in the study. . But, he added, “the real cat” is anything but simple.
Modern research has split the falling cat problem into two competing models.
The first, “legs in, legs out,” suggests that cats correct their falling trajectory by first extending their hind limbs before retracting them, using a sequential twist of their upper and then lower trunk to gain the proper posture while in free fall.
The second model, “tuck and turn,” suggests that cats turn their upper and lower bodies in simultaneous juxtaposed movements.
In the new study, Dr. Higurashi and his colleagues scrutinized different segments of cat spines using donated cadavers. They also conducted dropping experiments on a pair of live cats, from about three feet up.
“To prevent injury, we placed a thick, soft cushion at the landing site,” Dr. Higurashi said. “One of our undergraduate students did the dropping.”
His team also built a device to physically test the flexibility of the spines. After removing the spines from the cadavers, they systematically bent and contorted sections of vertebrae with mechanical claws while measuring how significantly they rotated.
They compared their observations with their video footage of the live cats. The recordings were analyzed frame by frame.
The researchers found that the feline spine was extremely flexible in the upper thoracic vertebrae, but stiffer and heavier in the lower lumbar vertebrae. The discovery matches video evidence showing the cats first turn their front legs, and then their lower legs. The results suggest the cat quickly spins its flexible upper torso to face the ground, allowing it to see so that it can correctly twist the rest of its body to match.
“The thoracic spine of the cat can rotate like our neck,” Dr. Higurashi said.
Experiments on the spine show the upper vertebrae can twist an astounding 360 degrees, he says, which helps cats make these correcting movements with ease. The results are consistent with the “legs in, legs out” model, but definitively determining which model is correct will take more work, Dr. Higurashi says.
The results also yielded another discovery: Cats, like many animals, appear to have a right-side bias. One of the dropped cats corrected itself by turning to the right eight out of eight times, while the other turned right six out of eight times.
Even though the study does not resolve the falling cat problem, Dr. Belyaev said it provided “insights for physicists on how to adjust their mechanical models to better match the real-life properties of a cat.”
In future research, Dr. Higurashi and his colleagues plan to collect more data on falling cats to construct updated mathematical and 3-D models. Perhaps those models will crack the case of the free-falling feline.
“A lot of scientists, historically, have looked for the ‘one true way’ that cats land on their feet,” Dr. Gbur wrote in an email. But, he added, “nature is unconcerned with simplicity.”
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