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AP®︎/College Biology

Course: AP®︎/College Biology > Unit 8

Lesson 1: Responses to the environment
Science
AP®︎/College Biology
Ecology
Responses to the environment
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Animal communication

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Learn how animals communicate with visual, sound, touch, and chemical signals.

Key points

  • Communication is when one animal transmits information to another animal causing some kind of change in the animal that gets the information.
  • Communication is usually between animals of a single species, but it can also happen between two animals of different species.
  • Animals communicate using signals, which can include visual; auditory, or sound-based; chemical, involving pheromones; or tactile, touch-based, cues.
  • Communication behaviors can help animals find mates, establish dominance, defend territory, coordinate group behavior, and care for young.

Introduction

Have you ever wondered how ants follow what seem to be invisible trails leading to food? Why male dogs mark their territory by peeing on bushes and lampposts when you take them for a walk? What birds are saying to one another when they chirp outside your window?
If so, you're in the right place! In this article, we'll take a look at these—and many other—forms of communication used in the animal kingdom.

Communication takes many forms

Communication—when we're talking about animal behavior—can be any process where information is passed from one animal to another causing a change or response in the receiving animal.
Communication most often happens between members of a species, though it can also take place between different species. For instance, your dog may bark at you to ask for a treat! Some species are very social, living in groups and interacting all the time; communication is essential for keeping these groups cohesive and organized. However, even animals that are relative loners usually have to communicate at least a little, if only to find a mate.
What forms can communication behaviors take? Well, animal sensory systems vary quite a great deal. For instance, a dog's sense of smell is 40 times more acute than ours!squared Because of this sensory diversity, different animals communicate using a wide range of stimuli, known collectively as signals.
Below are some common types of signals:
  • Pheromones—chemicals
  • Auditory cues—sounds
  • Visual cues
  • Tactile cues—touch
In some cases, signals can even be electric!
Where does this diversity of communication behaviors come from? Like other traits, communication behaviors—and/or the capacity for learning these behaviors—arise through natural selection. Heritable communication behaviors that increase an organism's likelihood of surviving and reproducing will tend to persist and become common in a population or species.
In the rest of the article, we'll look at some examples of the many ways that animals can communicate with one another.

Pheromones

A pheromone is a secreted chemical signal used to trigger a response in another individual of the same species. Pheromones are especially common among social insects, such as ants and bees. Pheromones may attract the opposite sex, raise an alarm, mark a food trail, or trigger other, more complex behaviors.
The diagram below shows pheromone trails laid down by ants to direct others in the colony to sources of food. When a food source is rich, ants will deposit pheromone on both the outgoing and return legs of their trip, building up the trail and attracting more ants. When the food source is about to run out, the ants will stop adding pheromone on the way back, letting the trail fade outstart superscript, 3, comma, 4, end superscript.
The diagram has an ant hill with 3 small images near it. The image on the left has a row of bright red dots leading to it, and 6 ants moving towards the image. The image on the right has 5 lighter colored dots and 1 ant from the ant hill and 2 ants from a different direction moving towards the image. The image in the center has 5 very faint red dots spaced further apart than the other dots and there is 1 ant moving from the ant hill and 1 moving from a different direction, both towards the image.
Image credit: Knapsack ants by Dake, CC BY 2.5
Ants also use pheromones to communicate their social status, or role, in the colony, and ants of different "castes" may respond differently to the same pheromone signalscubed. A squashed ant will also release a burst of pheromones that warns nearby ants of danger—and may incite them to swarm and stingstart superscript, 5, comma, 6, end superscript.
Dogs also communicate using pheromones. They sniff each other to collect this chemical information, and many of the chemicals are also released in their urine. By peeing on a bush or post, a dog leaves a mark of its identity that can be read by other passing dogs and may stake its claim to nearby territorystart superscript, 7, comma, 8, end superscript.

Auditory signals

Auditory communication—communication based on sound—is widely used in the animal kingdom.
Auditory communication is particularly important in birds, who use sounds to convey warnings, attract mates, defend territories, and coordinate group behaviors. Some birds also produce birdsong, vocalizations that are relatively long and melodic and tend to be similar among the members of a species.
A photograph of a barn swallow with its beak wide open.
Image credit: Barn swallow (Hirundo rustica rustica) singing by Charles J. Sharp, CC BY-SA 4.0
Many non-bird species also communicate using sound:
  • Monkeys cry out a warning when a predator is near, giving the other members of the troop a chance to escape. Vervet monkeys even have different calls to indicate different predators.
  • Bullfrogs croak to attract female frogs as mates. In some frog species, the sounds can be heard up to a mile away!
  • Gibbons use calls to mark their territory, keeping potential competitors away. A paired male and female, and even their offspring, may make the calls together.
Water, like air, can carry sound waves, and marine animals also use sound to communicate. Dolphins, for instance, produce various noises—including whistles, chirps, and clicks—and arrange them in complex patterns. The idea that this might represent a form of language is intriguing but controversialstart superscript, 9, end superscript.

Visual signals

Visual communication involves signals that can be seen. Examples of these signals include gestures, facial expressions, body postures, and coloration.
Gesture and posture are widely used visual signals. For instance, chimpanzees communicate a threat by raising their arms, slapping the ground, or staring directly at another chimpanzee. Gestures and postures are commonly used in mating rituals and may place other signals—such as bright coloring—on display.
Facial expressions are also used to convey information in some species. For instance, what is known as the fear grin—shown on the face of the young chimpanzee below—signals submission. This expression is used by young chimpanzees when approaching a dominant male in their troop to indicate they accept the male's dominance.
A photograph of a chimpanzee with a fear grin expression on its face.
Image credit: The 'fear grin' by CK-12 Foundation, CC BY-NC 3.0
Changes in coloration also serve as visual signals. For instance, in some species of monkeys, the skin around a female’s reproductive organs becomes brightly colored when the female is in the fertile stage of her reproductive cycle. The color change signals that the female can be approached by suitors.
An organism's general coloration—rather than a change in color—may also act as a visual signalstart superscript, 1, end superscript. For instance, the bright coloration of some toxic species, such as the poison dart frog, acts as a do-not-eat warning signal to predators.
A photograph of a poison dart frog. The frog’s legs are blue, and the body has a stripped orange and black appearance.
Image credit: Ranitomeya amazonica by Vir Vikram Singh, CC BY-SA 3.0

Tactile signals—touch

Tactile signals are more limited in range than the other types of signals, as two organisms must be right next to each other in order to touchstart superscript, 10, end superscript. Still, these signals are an important part of the communication repertoire of many species.
Tactile signals are fairly common in insects. For instance, a honeybee forager that's found a food source will perform an intricate series of motions called a waggle dance to indicate the location of the food. Since this dance is done in darkness inside the nest, the other bees interpret it largely through touchstart superscript, 11, comma, 12, end superscript.
Tactile signals also play an important role in social relationships. For instance, in many primate species, members of a group will groom one another—removing parasites and performing other hygiene tasksstart superscript, 13, end superscript. This largely tactile behavior reinforces cooperation and social bonds among group membersstart superscript, 14, end superscript.
A photograph of 3 baboons sitting in a row grooming each other.
Image credit: Macaca fuscata, social grooming by Noneotuho, CC BY-SA 3.0
Tactile stimuli also play a role in the survival of very young organisms. For instance, newborn puppies will instinctively knead at their mother's mammary glands, causing the release of the hormone oxytocin and production of milkstart superscript, 15, end superscript.

What is communication used for?

As the examples above illustrate, animals communicate using many different types of signals, and they also use these signals in a wide range of contexts. Here are some of the most common functions of communication:
  • Obtaining mates. Many animals have elaborate communication behaviors surrounding mating, which may involve attracting a mate or competing with other potential suitors for access to mates.
  • Establishing dominance or defending territory. In many species, communication behaviors are important in establishing dominance in a social hierarchy or defending territory.
  • Coordinating group behaviors. In social species, communication is key in coordinating the activities of the group, such as food acquisition and defense, and in maintaining group cohesion.
  • Caring for young. Among species that provide parental care to offspring, communication coordinates parent and offspring behaviors to help ensure that the offspring will survive.
As these examples show, communication helps organisms interact to carry out basic life functions, such as surviving, obtaining mates, and caring for young.

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