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This photo isn’t a fake. It’s a real frog—the biggest one on Earth. The goliath frog can weigh more than 7 pounds and measure a foot long. Scientists recently discovered that these amphibians are also superstrong construction workers: They move heavy rocks to build nests for their young.

Most types of frogs find shallow pools of water where they will lay their eggs. But researchers found that goliath frogs use their powerful legs to dig their own holes. They clear out leaves and gravel—and even rocks that weigh more than 4 pounds! They arrange the stones in a circle around the edge of the pool to protect their young.

“These frogs are amazing,” says Marvin Schäfer, who led the research team. “They have to be this giant to move these massive rocks.”

You won’t find goliath frogs in your local pond, however. They live only in rainforests in two countries in Africa.