Ostriches have no teeth and swallow small stones to aid their digestion and grind food in the gizzard. An adult ostrich carries about 1kg (2.2 lb) of stones in its stomach. Ostriches can go without drinking for several days, using metabolic water and moisture in ingested plants.
In their natural environment ostriches normally spend the winter months in pairs or alone. During breeding season and sometimes during extreme rainless periods ostriches live in nomadic groups of five to 50 birds, led by a top hen.
Ostriches become sexually mature between the ages of two and four years; females mature about six months earlier than males. Eggs are laid early spring to autumn, weighing between 1kg (2.2lb) to 2kg (4.4lb). Ostriches are oviparous. The females will lay their fertilized eggs in a single communal nest, a simple pit, 30 to 60 centimeters (12–24 in) deep and 3 meters (9.8 ft) wide, scraped in the ground by the male. The dominant female lays her eggs first, and when it is time to cover them for incubation she discards extra eggs from the weaker females, leaving about 20 in most cases.
Ostriches were almost wiped out in the 18th century due to hunting for feathers. By the middle of the 19th century, due to the extensive practice of ostrich farming the ostrich population increased. The movement changed to domesticating and plucking ostriches, instead of hunting. Ostriches have been successfully domesticated and are now farmed throughout the world, particularly in South Africa, for meat, feathers and leather. The leather goes through a tanning process and is then manufactured into fashion accessories such as handbags, belts and purses. It is also used in the car and aviation industries, as well as to upholster furniture.
Ostriches produce the strongest commercially available leather, which is supple and has a distinctive quill pattern. Ostrich meat tastes similar to lean beef and is low in fat and cholesterol, as well as high in calcium, protein and iron.
Recently the ostrich industry in South Africa, the largest in the world, has reached crisis point as various outbreaks of the H5N2 bird flu virus has been detected. Although this virus cannot be transmitted to humans, government regulation has required the culling of all ostriches affected with this strain of bird flu. Over 43 000 birds have been culled in South Africa since last year, many of these breeding birds. This has had serious repercussions on the industry, with many farms hatching no new chicks, while been forced to cull existing flocks. There is currently speculation that ostriches may become an endangered species.