Yamaguchi University reveals "cat air-righting" ability lies in the spine: Easily twistable thoracic spine is key to success

A research group at Yamaguchi University has revealed that the key to "cat air-righting," the phenomenon where a cat dropped from a high place repositions its body mid-air to land on its feet, lies in its spine. The study found that a cat's thoracic spines are significantly more flexible and twistable compared to its lumbar spines, allowing it to turn its upper body around first.

According to Assistant Professor Yasuo Higurashi, who studies Functional Morphology, of the Joint Faculty of Veterinary Medicine at Yamaguchi University, cat posture reorienting is scientifically termed "air-righting." While physicists have advanced research by modeling this movement, actual anatomical studies utilizing cats have been limited.

Higurashi conducts research owing to his interest in the relationship between the spinal column and body movements in mammals, including cats and dogs. In this study, he extracted the spinal columns from five cats undergoing pathological autopsy to measure the twistability of each section and explore its relationship with air-righting.

The researchers harvested the thoracic spines (standardly consisting of 13 spines) and the lumbar spines (7 spines), along with the surrounding soft tissues such as ligaments and intervertebral discs. Using a load-testing machine designed to evaluate material strength, they examined how much twisting force the specimens could withstand.

For the thoracic spines, there was a "neutral zone" where the spine could be twisted left and right up to an angle of 47 degrees with almost no resistance. Beyond 47 degrees, resistance gradually intensified, and the specimens could no longer withstand the load once the twisting angle reached approximately 171 degrees. On the other hand, the lumbar vertebrae possessed almost no neutral zone, and strong resistance was encountered immediately upon twisting, reaching its limit at an angle of around 57 degrees. This demonstrated that a cat's thoracic spines are exceptionally easy to twist, while its lumbar vertebrae are highly resistant to twisting.

Next, the team captured videos of the air-righting in two live cats to analyze their physical movements. When a cat was released upside down in mid-air, the rotation of its upper body was completed before the rotation of its lower body. This movement aligns consistently with the load-testing machine measurements showing that "the thoracic spines twist easily while the lumbar vertebrae do not."

Higurashi intends to conduct detailed future investigations into the forward, backward, and lateral bending properties, in addition to twisting, for each individual vertebra making up the thoracic and lumbar regions of cats. He stated, "In addition to the cat air-righting, I want to study how these properties relate to the uniquely high jumping ability of cats." The study was published in February in the online edition of The Anatomical Record, a journal of the American Association for Anatomy.