The transfer of information from one animal to another is called communication. It requires a sender and receiver. Both these animals are mutually adapted to each other. One animal acts as the sender. It must send a clear signal to the receiver. Communication can be:
(a) Intraspecific communication: These commutations occur within species. Intraspecific communication is especially important for reproductive success.
(b) Interspecific communication: These commutations occur between species. Examples of interspecific communication are warning signals. These signals are rattle on the tail of rattlesnake and the skunk’s presentation of its hindquarters and tail.
Animals use a variety of modalities for communication. These modalities include visual, auditory, tactile and chemical signals. Natural selection has influenced the characteristics of a signal system. Animals have evolved combinations-of signals. These signals are more effective than any single signal.
1. VISUAL COMMUNICATION •
Visual communication is important for • many animals. A large amount of information can be conveyed in a short time by visual communication.
- Most animals (e.g., cephalopod molluscs, arthropods, and most vertebrates offer than mammals) have well developed eyes have color vision.
- Many fishes, reptiles, and birds show brilliant color patterns. These patterns have a signaling function. ‘
- Most mammals have plain, darker colors. They are nocturnal (come at night). So they lack color vision. Their ancestors are nocturnal insethvores.
- Primates (man, monkey etc) have both color vision and colorful displays.
- There are bright facial markings on a male mandrill. Therefore, visual signal are present in them at all times.
- The signal may be hidden or located on a less exposed part of the body. These signals are then suddenly exposed. Some lizards like green anoles can change their color through activities of pigment cells in the skin.Disadvantages of visual signals
Visual signals have some disadvantages.
1. Sometimes various objects in the environment block the line of sight. Therefore, it is difficult to see these signals from a long distance.
2. Similarly, the signals are not effective at night. These signals can be detected by predators.
2. ACOUSTIC (SOUND) COMMUNICATION
Arthropods and vertebrates commonly use acoustic or sound communication. These animals spend energy to produce sounds. Sounds can be used during night or day. Sound waves also have advantage. They travel around objects. Therefore, open or hidden animals can produce or receive these signals. Sounds have many variations in frequency, duration, volume, and tone. Therefore, sounds can carry a large amount of information.
Acoustic communication systems are closely adapted to the environmental conditions. These communications send signal. For example:
- Tropical forest birds produce low frequency calls. These calls can pass easily through dense vegetation.
- Many primates produce sounds in tropical forests. These sounds travel over long distances.
- Some territorial birds sit on a high perch. It delivers the signal more effectively. Many small species of birds gives alarm calls.
- Most complex acoustic signals are studied in human and birds. These are birdsong and human speech.
3. TACTILE COMMUNICATION
The communications between animals by physical contact are called tactile communications. Their examples are antennae of many invertebrates and the touch receptors in the skin of vertebrates. They function in tactile communication. The birds preen the feathers of other birds. The primates groom each other.
4. CHEMICAL COMMUNICATION .
Chemical communication is a common method of communication. .Unicellular Organisms have chemoreceptors. They can recognize members of their own species with the help of chemoreceptors. Chemical signals are well developed iri insects, fishes, salamanders, and mammals. The chemical signals have following advantages:
- They.convey a simple message. This message can last for hours or days
- They are effective at night or day.
- They can pass around objects.
- They can be transported over long distances
- They take little energy to produce.Chemical signals also have disadvantages They cannot be changed quickly. They ct slowly.
Chemicals that are synthesized by one organism -and that affect the beha or of another member of the same species are called pheromones. Olfactory receptors are present in the receiving animal. They detect the chemical signal.. Many animals mark their territories by depositing odors. It acts as chemical signals for the other animals of the same species. For example, many male animals mark specific points in their territories with pheromones. These pheromones warn other males: The same pheromones also attract females in breeding condition.
Differences in the chemical structure of pheromones are directly related to their function. Pheromones are used for marking territories. They are used to attract mate The pheromones have higher molecular weights. Therefore, they last long time. Airborne signals have lower molecular weights. Thus they disperse easily For example, the sex attractant pheromones are present in female moths. Their pheromones are airborne. The males can detect them from several