Uricotelic

Uricotelic describes organisms that primarily excrete nitrogenous waste as uric acid or its salts (urates). This strategy contrasts with ammonotelic organisms, which excrete ammonia, and ureotelic organisms, which excrete urea. Uricotelism is common in terrestrial animals and is an adaptation to conserve water, since uric acid is relatively insoluble and can be eliminated with minimal water loss.

In birds, reptiles, and many terrestrial insects, nitrogenous waste is converted to uric acid and transported to the excretory system. In birds and most reptiles, the kidneys produce a urine rich in uric acid that is discharged into the cloaca and excreted together with feces as a white, pasty excretion. In insects, Malpighian tubules secrete uric acid into the gut, where it is eliminated with feces as urate crystals or paste.

Ecological and evolutionary significance centers on water conservation. The ability to excrete uric acid with little water supports life in arid or open habitats, aids in high-activity lifestyles such as flight, and reduces the volume of water lost with waste. The trade-off is a relatively high energetic cost to synthesize uric acid from nitrogenous substrates.

Examples of uricotelic organisms include birds (e.g., chickens, songbirds), most reptiles (e.g., lizards and snakes), and many insects (e.g., beetles, grasshoppers). Some species produce mixtures of waste forms, and uric acid excretion can vary with developmental stage, diet, and environmental conditions.