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Like aging divas, animals aren't exactly up-front about their birthdays. Researchers estimate their age by counting growth rings on shells or marking part of an animal and checking back every year. The resulting life spans are only educated guesses, but we turned up a few candidates for most candles on the birthday cake. The oldest animal on the planet may be the deep-sea tubeworm Lamellibrachia, found in the Gulf of Mexico. These skinny tubes live in colonies, and each creature can live around 170
to 250 years. Another long-lifer is the ocean quahog Arctica islandica (a type of clam). According to radiometric dating, one specimen was 220 years old. Many of these clams live over 100 years. The best-documented old folks in the animal world are tortoises. In March 2006, an Aldabra tortoise at the Calcutta Zoo died and was estimated to be 250 years old. A Madagascar radiated tortoise lived in captivity to at least 188. A 176-year-old giant tortoise from an Australian Zoo died in June, 2006. Typically, the Galapagos tortoise lives 150 years. Other varieties regularly live to be 100. Bottom line -- all these senior citizens have us humans beat, what with our measly 64-year life expectancy and record-holding 120-year-old guy.
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