Close behind chemical communication is tactile messaging. The most common touch behavior among ants is to stroke each other with antennae while passing each other on the trail. Like bees, ants employ other tactile displays, including waggling, jerking, and dancing, which seem to excite and recruit nest mates to perform various tasks.
Communication by Sound
Friend or Foe?
Friend or foe? These worker ants (Oecophylla longinoda) encounter each other and take a quick sniff of each other’s scent. Photo © Alex Wild
Scientists used to wonder whether ants could hear at all because they were unresponsive to loud human noises. For the past hundred years scientists have known that ants could detect ground vibrations but thought they couldn’t detect sounds from the air. Research now suggests that some ants can detect sounds from other ants through the air, using hair-like sensors at the tips of their antennae.3
Through their knees they are very adept at sensing vibrations from the nest, ground, and surrounding leaves. Using this sound, they can locate lost family members and prey. During a nest’s cave-in, leaf-cutter ants detected sound from their trapped family members, 2 inches (5 cm) deep, and started digging toward them.
It makes sense that ants can detect sound because they make sound. Many ants produce squeaky sounds by rubbing one body part against another (called stridulating). They also produce sounds by jaw slapping.
When a Malaysian ponerine army ant colony is ready to emigrate, workers will slap their jaws together. The sound is amplified by surrounding leaves and signals the colony to break camp. A carpenter ant species that builds silk nests in trees can sound an alarm when the nest is disturbed or when carbon dioxide reaches dangerous levels. One or two ants will tap their abdomens against the nest, causing others to do the same. The noise can be as loud as human conversation.
Some species ingeniously combine all three communication techniques—chemicals, touch, and sound—to convey their messages to cohorts.