Animal Communication

I

Introduction

Animal Communication, interaction between animals in which information transmitted from one animal or group of animals affects the behavior of other animals. Animals typically exchange information using a signal, such as facial expression, sound, or touch. Communication between animals helps them coordinate the vital functions of their lives—namely, gathering food and hunting, staking out territory, mating, caring for young, and defending themselves.

Most commonly, animal communication is intraspecific (occurring between animals of the same species). Mating signals are perhaps the most important intraspecific communication, since animals must be able to identify and attract a potential mate in order to reproduce. The loud roar of a male elephant seal, for example, directs females where to come ashore for breeding. Intraspecific communication also helps distinguish individuals in a particular animal group. Mother gulls learn to recognize the individual calls of their own chicks so that they can quickly find their babies in densely populated gull colonies.

Communication can also be interspecific, occurring between different animal species. Many animals who share habitats learn to use signals from other species as warnings for approaching danger. Langurs (tree-living monkeys of Asia and East India) respond to the alarm cries or flights of peacocks and deer. Similarly, in Africa, grazing animals such as wildebeests and waterbucks pay close attention to the keen-eared zebra. If a nearby zebra suddenly jumps up and runs, the other animals follow to escape a common predator.

II

Influences on Communication

The higher an animal’s position on the evolutionary scale, the more complex its sense organs and the more elaborate its apparatus for producing communication signals. A few animals, notably the primates, transmit information by multiple signals, such as a combination of gestures, facial expressions, and sounds. This use of multiple signals makes possible a more extensive vocabulary for communicating, which in turn enables animals to transmit more complex information.

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Physical characteristics play a strong role in determining the types of messages that are transmitted or received. Primates, who have superior vision, rely heavily on visual signals. In contrast, insects see only vague images, so they concentrate more on chemical and tactile messages. Scent organs in most insects’ antennae and taste organs in their feet help them use these senses very effectively. Animals whose means of movement leaves no appendages free for signaling must develop other ways of communicating. Scientists believe, for instance, that birds developed their complex language of song along with the evolution of flight: with their wings occupied with flying, birds learned to rely primarily on sound rather than body movement for communication.

Communication also varies according to habitat, since where an animal lives influences how information travels between sender and receiver. For example, fish, marine mammals, and aquatic invertebrates all depend on the transmitting capacity of water for communication. Clams, barnacles, and similar invertebrates communicate by opening and snapping shut their shells, and the resulting small sounds are amplified considerably in water. Bird species that live in thickly wooded habitats, where trees impede vision, rely primarily on sound signals to contact other birds. In contrast, birds living where vegetation is sparse are more likely to depend on visual signals, including colorful plumage that indicates a bird’s age or gender.

Social patterns have significant impact on communication as well. Solitary birds, having no one else with whom to communicate, may sing just one song over and over, whereas flocking birds, such as geese, use a wide array of calls. These calls communicate distinct messages to other members of the flock, from “Danger!” and “All clear!” to calls indicating that food is near or that the flock is about to take flight. Social patterns have a particularly strong influence on communication habits in primates. For this reason, researchers such as British ethologist Jane Goodall have been able to discover complex social structures among chimpanzees and other primates by documenting and analyzing communication transactions.

III

Innate or Learned?

Most animal behaviorists today believe that two major influences determine animal behavior, including communication. One influence is innate, or programmed by genes; the other is learned, or gained by experience. Either genes or experience can take a greater role, depending on the species and the behavior in question.

Animal communication that is primarily innate includes signaling based on fixed action patterns. Fixed action patterns are genetically encoded and occur spontaneously when the animal is presented with an environmental cue, or sign stimulus, which acts as a trigger. Researchers have observed a vivid example of this behavior in the male stickleback fish, who flaunts his flame-red belly in fighting postures when another male invades his territory at mating time. A male stickleback will produce the same postures when confronted with models of fish showing bright red undersides. These postures are fixed action patterns because the red coloring—the sign stimulus—provokes identical behavior in all male sticklebacks.

In contrast, communication as learned behavior is clearly demonstrated in birds, whose songs are often influenced by other birds. The white-crowned sparrow, for example, has a rudimentary song coded in its genes but modifies the song to match that of other white-crowned sparrows living nearby. Researchers have found that young white-crowned sparrows living in isolation the first few months of their lives never develop their songs past the rudimentary version. This critical period—the time where early learning must take place—is a common feature of learned behavior in animals.

IV

Communication by Visual Display

Visual displays include a rich array of facial expressions, body movements, coloration, and physical shapes, such as the male peacock’s fanned tail. Visual communication is easy to produce, instantaneous, and can be modified to carry various types of information. For example, a dog may raise its hackles (long, erectile hairs on the back of its neck) in warning when a potential enemy approaches and then lower them if the approaching animal or human appears friendly.

Visual displays can be momentary, such as raised hackles; cyclical, such as the reddened rump of a female chimpanzee that signals readiness for mating; or permanent, as evident in the scarlet and purple facial markings of a male mandrill that enhance his facial expressions. They can be as simple as a male stickleback’s reddened belly, or as complex as a mountain gorilla’s dominance ritual, which includes rising to a standing position, chest-slapping, tipping the head to one side, and tearing up and tossing vegetation.

Different aspects of an animal’s body may be used in visual display, depending on both individual anatomy and environment. Most reptiles, for instance, have body parts that inflate (the flared neck skin, or hood, of the cobra) or vibrate (the tail of the rattlesnake) to show aggression. Animals living on land, including humans and other primates, rely primarily on the head and face for producing visual displays. Fish, in contrast, use their gills and fins. Some structures used for visual display serve additional functions as well. Antlers of male deer are used both for display—signaling their gender and dominance—and for fighting other males.

Visual communication is used to some extent by nearly all animals, although those with limited vision—for example, cave-dwelling bats—do not depend primarily on this sense. Visual signals have some limitations, as they generally require light and an unimpeded view to be seen. An exception is the display of fireflies, who generate their own pulsating light to attract mates in the darkness.

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