Friday, April 20, 2012

Tool-Using Monkeys?

Many years ago, it was thought that human beings were different from all other animals because people used tools and animals did not. But new information shows us that we are not alone in using tools.

Many of us have seen how otters float on their backs while breaking open shellfish by hammering them on a stone held on their stomachs. Now, it seems, otters aren’t the only ones who use stones to harvest oysters and other shellfish.

Thai scientists were studying the impact of the tsunami that ravaged the southeast Asian coast in December 2004. They noticed a pair of female long-tailed macaques using some type of object to crack open mollusk shells so they could scoop out and eat the animals inside. Curious, they landed and discovered cracked oyster shells scattered on the beach along with axe-shaped stones that the monkeys had used to break them open.

Further investigation revealed that this behavior was common among the macaques living along this stretch of coast, and that the monkeys were regular visitors to the beach. It seems that the macaques not only cracked shells open with their tools, but they also used them to dislodge their prey from the rocks. They also discovered that the monkeys had a special fondness for crabs, which were also broken open using their stones.

Interviews with local islanders showed that the animals’ behavior was a year-round practice. They also said that when the macaques were foraging in mangrove swamps which did not contain suitable stones, the monkeys used empty oyster shells in their place.

Surprisingly, the long-tailed macaques’ odd behavior had been reported 120 years before by Alfred Carpenter of the Marine Survey Office in Bombay, India. In an article written for the journal Nature, Carpenter described how macaques living on islands of the Mergui Archipelago in South Burma were already using stone ‘hammers’ to crack open oyster shells. He also said that the monkeys frequently carried their stones up to 80 yards, which indicates that the monkeys were very careful in their tool selection. Somehow, though, his observations were either overlooked, or not taken seriously, until the new information was published in 2007.

How many other animals are using tools? Many new examples are coming to light and I’ll be investigating these claims over the next several months.

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