Mice have bones. Like humans and other mammals, mice possess a complete skeletal system. This internal framework provides the structure and support necessary for their bodies, allowing them to move and function.
The Vertebrate Connection
Mice are classified as vertebrates, a group of animals characterized by the presence of a backbone or spinal column. This classification places them alongside fish, amphibians, reptiles, birds, and other mammals, all of which share this fundamental anatomical feature. In contrast, invertebrates, such as insects or worms, lack an internal bony skeleton.
This internal skeleton, also known as an endoskeleton, provides a rigid yet flexible support system. It is composed of numerous bones that grow with the animal, unlike the external exoskeletons found in some invertebrates.
What Bones Do for Mice
The skeletal system in mice performs several essential functions. Bones provide structural support, giving the mouse its characteristic shape and holding its body upright. They also serve to protect internal organs, with the skull encasing the brain and the rib cage shielding the heart and lungs from external impact.
Bones also play a role in movement, acting as attachment points for muscles. When muscles contract, they pull on bones, allowing the mouse to run, jump, and climb with agility. Beyond these mechanical roles, bones are involved in biological processes such as blood cell production within the bone marrow and the storage of minerals like calcium and phosphorus.
Squeezing Through Small Spaces
A common observation is a mouse’s remarkable ability to squeeze through seemingly impossible openings, which might lead some to question if they have bones. While mice do possess a full skeletal system, their bodies are uniquely adapted for flexibility. Their rib cages are particularly pliable, allowing for a greater degree of compression than in many other mammals.
Mice can fit through any opening that their skull can pass through, typically as small as a dime or about a quarter-inch (6-7 mm) wide. This is partly because they lack rigid collarbones, which would otherwise restrict their ability to flatten their bodies. The skull is the most rigid part of a mouse’s skeleton, effectively setting the limit for the size of the gaps it can navigate.