Animal Communication: Chemical, Visual, and Auditory

Animal communication is the transfer of information from a sender to a receiver using signals, and the main types of signal are chemical (pheromones), visual (color, posture, light), auditory (calls and songs) and tactile. In brief: communication evolves when it benefits both sender and receiver, or at least the sender. Ants lay chemical trails, fireflies flash patterns of light, frogs and birds call, and honeybees pass the direction and distance of food by the waggle dance. Each channel has advantages and disadvantages, depending on distance, habitat and risk of detection by predators.

Signals coordinate mating, feeding, defense and group living. This guide explains what makes a signal and the main channels, with examples, how honeybee dances work, how signals can be honest or deceptive, compares the channels in a table, works through a calculation of the location of food from a bee dance and corrects common mistakes.

What is animal communication?

Communication occurs when a signal from one animal (the sender) changes the behavior of another (the receiver). The signal has evolved because it has a beneficial effect, in general, for the sender. A message can warn of danger, attract a mate, advertise a territory, beg for food, signal aggression or submission, or coordinate a group. Signals are distinct from cues: a cue, such as the smell of a prey animal, gives information, but it was not shaped by natural selection for that purpose.

Signals may be honest, giving reliable information about the sender (for example, the loud, deep roar of a large red deer stag is difficult to fake, and shows his strength) or deceptive (some fireflies of the genus Photuris mimic the flash patterns of other species to attract and eat males). Costly signals, such as the peacock’s tail, tend to be honest because they can only be produced by individuals in good condition.

What is chemical communication?

Chemical signals are the oldest and most widespread form. Pheromones are chemicals released by an animal that affect the behavior or physiology of others of the same species.

• Sex pheromones: a female silk moth releases bombykol, which can be detected by males several kilometers downwind, using feathery antennae that can respond to a few molecules. Male moths fly up the concentration gradient.
• Trail pheromones: ants that find food lay a trail while returning to the nest, and others follow and reinforce it. The trail evaporates when food is exhausted, so the system corrects itself.
• Alarm pheromones: released by injured aphids, bees and fish to warn others.
• Queen substance: in honeybees, the queen’s pheromones suppress the development of ovaries in workers, and keep the colony together.
• Territorial marking: dogs, cats and many mammals mark with urine and scent glands.
• Recognition: animals identify kin, mates and colony members by scent, as with ants and mice.

The advantages are that signals last for a long time, work in the dark and around obstacles, and travel long distances. The disadvantages are that they are slow to change, difficult to direct and can be used by predators. Many fish release alarm substances when the skin is damaged.

What is visual communication?

Visual signals work well in daylight and over short to medium distances, and they can change quickly. They include:

• Color and patterns: the red belly of a male stickleback, the bright feathers of birds-of-paradise, and the warning coloration of poisonous frogs. Cuttlefish and chameleons change color rapidly to signal mood.
• Postures and displays: a dog showing its teeth, wolves lowering the body in submission, birds spreading wings, and courtship dances of cranes and grebes.
• Facial expressions and gestures: especially in primates. Chimpanzees use more than 60 gestures.
• Bioluminescence: fireflies flash species-specific patterns to attract mates. Deep-sea anglerfish use a lure of light to attract prey.
• Movements: the white tail flag of deer raised when alarmed.

What is auditory communication?

Sound travels over long distances, around obstacles, in the dark and in water, and can carry rich information. It can be changed quickly. However, it can also be heard by predators and eavesdroppers.

• Bird song: mainly used by males to attract mates and defend territories. The song is learned in many species (songbirds), and shows regional dialects. Calls are shorter and signal alarm or contact.
• Frog and insect calls: male frogs and crickets call to attract females, and species-specific calls prevent mating between species. The calls of crickets depend on temperature: the faster chirping at higher temperatures is the basis of Dolbear’s law (counting chirps in 14 seconds and adding 40 gives approximately the temperature in °F).
• Whale song: male humpback whales sing complex songs of up to 20 minutes that are shared by the whales in a region and change over the years. Sound in water can travel hundreds of kilometers for the low-frequency calls of blue and fin whales.
• Echolocation: bats and dolphins make high-pitched sounds and use the echoes to find objects and prey. It is mainly used for navigation, though bats also produce social calls.
• Alarm calls: vervet monkeys have different calls for leopards, eagles and snakes, and the other monkeys respond appropriately: they climb trees on hearing the leopard call, look up for eagles and scan the ground for snakes (Cheney and Seyfarth). Prairie dogs have different alarm calls for different predators.
• Infrasound: elephants communicate with very low sounds that travel for kilometers through the ground and air.

What other channels are there?

Tactile communication by touch: grooming in primates to strengthen bonds, and antennae touching in ants for food exchange. Electrical signals: electric fish such as the elephantnose fish generate weak electric fields and communicate with them. Vibrations: spiders signal with vibrations on the web, and male wolf spiders drum on leaf litter. Many animals use more than one channel (multimodal signals) to give more reliable messages.

Communication channels compared

How does the honeybee waggle dance work?

Karl von Frisch discovered that a forager bee that has found a good food source returns to the hive and performs a dance on the vertical surface of the comb, in the dark, and nearby bees follow it by touch and by sensing the vibrations. If the food is close (less than about 50 to 100 meters), the bee performs a round dance, which tells the others to search near the hive. If the food is farther away, she dances the waggle dance, in a figure of eight with a straight “waggle run” in the middle, during which she shakes her abdomen.

• Direction: the angle of the waggle run relative to the vertical shows the direction of the food relative to the sun. Straight up on the comb means “fly toward the sun”. An angle of 60° to the right of the vertical means 60° to the right of the sun’s direction.
• Distance: the duration of the waggle run is related to the distance, roughly 1 second for about 1 kilometer (the exact relation differs among bee races).
• Quality: the vigor and number of repeats show how rich the source is.
• The bees correct for the movement of the sun during the day, using their internal clock.

Worked example: reading a waggle dance

It is a sunny day, and the sun is in the south, at a compass bearing of 180°. A forager performs a waggle dance in which the waggle run points 60° to the right of the vertical (up), and lasts 2.0 seconds. Assume that 1 second of waggling corresponds to 1 kilometer.

1. Direction relative to the sun: the vertical represents the direction of the sun. 60° to the right means that the food is 60° clockwise from the direction of the sun.
2. Compass bearing: 180° + 60° = 240°, which is toward the south-west (bearings: north 0°, east 90°, south 180°, west 270°).
3. Distance: 2.0 seconds × 1 km per second = 2 km.
4. Prediction: new bees will leave the hive and fly 2 km on a bearing of 240°.

Because the sun moves across the sky, the angle of the dance for the same patch of flowers changes during the day. Later, when the sun is in the west (270°), a dance for the same flowers at bearing 240° would point 30° to the left of the vertical (270° − 240° = 30°). Von Frisch’s experiments showed that recruits found a feeder from the dance alone, and later work with robot bees and radar tracking confirmed that recruits follow the information. The relation between waggle duration and distance differs among bee races, so a distance estimate from the dance is approximate.

How was animal communication studied?

Karl von Frisch decoded the bee dances in the 1940s, and shared the 1973 Nobel Prize in Physiology or Medicine with Lorenz and Tinbergen. Adolf Butenandt isolated the first pheromone, bombykol, in 1959, from half a million silk moths. Peter Marler studied birdsong learning in the 1950s and 1960s. Dorothy Cheney and Robert Seyfarth studied the alarm calls of vervet monkeys in the 1980s. Recent work includes the study of whale song and of the “language” of prairie dogs.

Which mistakes are common?

Mistake 1: Saying that pheromones act between different species

Pheromones, by definition, act between members of the same species. Chemicals used between species are allelochemicals.

Mistake 2: Thinking that all animal signals are learned

Many are innate, like the bee dance. Birdsong in songbirds is partly learned.

Mistake 3: Assuming that a signal is a cue

Signals evolved to convey information. Cues are incidental information.

Mistake 4: Ignoring costs

Signals can attract predators and use energy. The balance explains the form of signals.