Horse
Depending on breed, management and environment, the modern domestic horse has a life expectancy of 25 to 30 years. Uncommonly, a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was "Old Billy", a 19th-century horse that lived to the age of 62. In modern times, Sugar Puff, who had been listed in "Guinness World Records" as the world's oldest living pony, died in 2007 at age 56.
Namib Desert Horse
Due to scarcity of water, the Namib Desert Horse sometimes goes without water for as long as thirty hours in summer and has been known to go close to 72 hours without water during the winter, significantly longer than most horses, even other feral herds. A 1991 study suggested that in 75 years of genetic isolation and water scarcity the population had developed physiological mechanisms which improved their ability to conserve water. In 1993, a second study showed that the physiological water-conservation ability did not differ between Namib Desert Horses and other populations when dehydrated for periods of up to 60 hours, but suggested that the Namib Desert Horse would show improved conservation ability when dehydration periods were extended to upwards of 72 hours, a common occurrence in their feral state.