Some Ants Drop Stones On Their Rivals.
Tool use isn’t limited to vertebrates. Even insects have been known to use simple tools. For example, some species of ants use pebbles or sand to block or hide the entrance to their hill and keep invaders out of their colony. Not content to always play defense, cone ants use a similar technique to block the entrances of hills of other ant species. These ants have been observed dropping small rocks down the tunnel entrances of nearby ant colonies, trapping their enemies inside. This stone-dropping tactic prevents the rival ants from competing for food. Cone ants work in teams to block rival colonies and are often so successful that they end up depleting the other species’ population.