Adélie penguins steal rocks from their neighbors to build nests.

Adélie penguins live in massive colonies that can have over 500,000 birds. During the breeding season in October, stones are the only materials available to build nests. These stones are vital because they lift the eggs above the ground. This prevents melting ice water from touching the eggs and freezing the chicks inside.A study in the journal Antarctic Science found that penguins steal rocks in about 15 percent of nesting attempts. Searching for new stones takes a lot of energy, so stealing is often faster. A single nest can hold more than 200 pebbles. Males spend several days gathering these rocks and guarding them from other thieves.If a nest is too low, the egg is 40 percent more likely to fail because of moisture. Researchers have even seen female penguins trade mating rights with other males just to get more stones. This high demand for rocks creates constant tension and social interaction within the colony. Every stone counts for the survival of the next generation.