Ostriches, like all modern bird species, do not have teeth. As the world’s largest and heaviest living birds, they have developed a method for processing the food required to sustain their bodies. The absence of teeth necessitates a specialized adaptation for the mechanical breakdown of tough plant matter and other food sources.
The Avian Mouth Structure
The biological reason for the ostrich’s toothlessness is rooted in avian evolution. The bony structure of the ostrich’s jaw is not equipped with sockets for teeth, but is instead covered by a horny, keratinized sheath known as a beak. This beak is a lightweight yet resilient structure that is adapted for their feeding behavior.
The broad, flat beak serves primarily as a tool for grasping and tearing food rather than for chewing. An ostrich uses its beak to pluck leaves, strip seeds from grasses, and pick up small objects from the ground. Since the food is immediately swallowed whole, the function of crushing food is deferred to a later stage in the digestive tract.
The Ostrich Diet
Ostriches are classified as omnivores, consuming a wide variety of plant and animal matter. The bulk of their diet is herbivorous, consisting primarily of plants with high fiber content, such as grasses, shrubs, leaves, and flowers. They are known to forage selectively, with plant material making up a significant portion of their intake, including seeds, roots, and succulents.
Their omnivorous nature means they also consume small animals and insects, which provide protein. This can include invertebrates like locusts and grasshoppers, as well as small vertebrates such as lizards, mice, or snakes. The complexity and toughness of this varied diet, especially the fibrous plant components, demand a mechanism for physical processing once the food is ingested.
Nature’s Grinding Mill
Without the ability to chew, the ostrich relies on a muscular organ called the gizzard to perform the work of teeth. This organ is the second chamber of the bird’s stomach, following the proventriculus, where chemical digestion begins. The gizzard’s walls are composed of thick, powerful muscles that contract rhythmically, a process often described as a gastric mill.
To facilitate this grinding action, the ostrich swallows small stones, pebbles, and grit, which are collectively known as gastroliths. These objects are stored within the gizzard and act as internal millstones. The muscular contractions of the gizzard walls compress the food against the gastroliths, effectively pulverizing the tough fibers and seeds into a digestible pulp.
An adult ostrich may carry these stones, sometimes accounting for approximately one percent of its body weight. The continuous grinding within the gizzard causes the gastroliths to slowly wear down over time. As the stones erode and pass through the digestive system, the ostrich must continually ingest new pebbles to maintain the necessary grinding capacity for its high-fiber diet.