social

Communication that is tactile, or transmitted by touch, is especially important in social animals, including insects. Members of an ant colony, for example, almost constantly lick and nuzzle each other; these activities strengthen the ants' social bonds. Tactile communication in bees has particularly interested researchers because of its surprising complexity. When a foraging bee discovers a new food source, it returns to the hive and performs a detailed dance, a phenomenon first interpreted by Austrian zoologist Karl von Frisch. Information is communicated primarily by physical contact as hive mates follow and touch the dancing bee. The orientation and speed of the dance, as well as the size of the area covered by the dancer, tell the other bees precisely the distance to and location of the food. Touch and bodily contact are used most extensively by primates, particularly baboons, gibbons, and chimpanzees. These animals frequently seize each other in warm embraces and also may lightly touch, push, nibble, or actually kiss each other. Grooming is a more structured form of tactile communication that helps primates establish social dominance and strengthen emotional bonds. The effectiveness of tactile communication is limited by distance-one animal must be touching another in order to convey information. However, tactile communication can be done in total darkness or silence.

Chemical signals are probably the oldest form of communication among animals and the most widely used form across species as well. Sensed by taste or smell, these signals most likely evolved from hormones-chemicals that carry information between cells. Chemical signals sent and received by individuals of the same species are called pheromones. Pheromones are quite powerful: a few pheromone molecules released into the air or water through urine, sweat, or other bodily secretions are enough to influence another animal's behavior. Unlike visual, sound, or tactile signals, pheromones can persist in the environment for a long time. This is important for many cat species, for instance, because females often release pheromones signaling fertility without knowing when the males will receive them. Because of their long duration, however, pheromones are not effective carriers for complex or changing messages. Moreover, because they are emitted into air or water, the direction of these signals is determined more by air or water currents than by the sender. Rain and wind can also greatly weaken the effectiveness of pheromones. Chemical communication is a powerful tool, particularly for ensuring reproduction, marking territory, and alerting prey against predators. A male giraffe, for instance, determines the best time to mate by nudging the female until she urinates and then checking the odor to determine if she is fertile.