How do rats squeeze through? - briefly
Rats can fit through gaps as small as about 1 cm because their skeleton is highly flexible, with a loosely attached rib cage and a skull that can compress. Their spine bends sharply and the cartilage around the jaw collapses, enabling the body to contort and slip through narrow openings.
How do rats squeeze through? - in detail
Rats move through openings that appear too small by exploiting several anatomical and physiological adaptations.
Their skeleton lacks a rigid clavicle, allowing the shoulder girdle to collapse inward. The rib cage is composed of flexible cartilage rather than solid bone, so the thorax can flatten without damaging internal organs. Vertebrae are linked by highly mobile intervertebral joints, permitting the spine to bend laterally and vertically. The skull is narrow and can tilt, reducing the overall head profile.
Skin and fur are highly elastic, stretching to accommodate a temporary decrease in body volume. Muscular control enables the animal to contract abdominal and chest muscles, squeezing the torso while expanding the head and hindquarters in succession. This coordinated contraction–expansion cycle reduces the cross‑sectional area to less than the animal’s resting diameter.
Sensory whiskers detect gaps as small as a few millimeters. When a suitable aperture is located, the rat aligns its body with the longest axis of the opening, then:
- lowers the head first, using the narrow skull to enter,
- contracts the forelimbs and chest to pass the shoulders,
- extends the spine while the hindquarters follow,
- finally relaxes the muscles to expand back to normal size after clearing the gap.
The combination of a collapsible skeletal framework, stretchy integument, and precise muscular timing enables rats to traverse spaces considerably smaller than their nominal body width. This capability supports their success in urban environments, where structural cracks and pipe joints provide frequent routes for movement.