Animal communication
Animal communication is the transfer of information from one or a group of animals to one or more other animals that affects the current or future behavior of the receivers. Information may be sent intentionally, as in a courtship display, or unintentionally, as in the transfer of scent from the predator to prey with kairomones. Information may be transferred to an "audience" of several receivers. Animal communication is a rapidly growing area of study in disciplines including animal behavior, sociology, neurology, and animal cognition. Many aspects of animal behavior, such as symbolic name use, emotional expression, learning, and sexual behavior, are being understood in new ways.
When the information from the sender changes the behavior of a receiver, the information is referred to as a "signal". Signalling theory predicts that for a signal to be maintained in the population, both the sender and receiver should usually receive some benefit from the interaction. Signal production by senders and the perception and subsequent response of receivers are thought to coevolve. Signals often involve multiple mechanisms, e.g., both visual and auditory, and for a signal to be understood, the coordinated behavior of both sender and receiver requires careful study.
Animal languages
The sounds animals make are important because they communicate the animals' state. Some animals species have been taught simple versions of human languages. Animals can use, for example, electrolocation and echolocation to communicate about prey and location.Modes
Visual
;Gestures: Most animals understand communication through a visual display of distinctive body parts or bodily movements. Animals will reveal or accentuate a body part to relay certain information. The parent herring gull displays its bright yellow bill on the ground next over its chick when it has returned to the nest with food. The chicks exhibit a begging response by tapping the red spot on the lower mandible of the parent herring gull's bill. This signal stimulates the parent to regurgitate food and completes the feeding signal. The distinctive morphological feature accentuated in this communication is the parent's red-spotted bill, while the tapping towards the ground makes the red spot visible to the chick, demonstrating a distinctive movement. Frans de Waal studied bonobos and chimps to understand if language was somehow evolved by gestures. He found that both apes and humans only use intentional gestures to communicate.;Facial expression: Another important signal of emotion in animal communication are facial gestures. Blue and Yellow Macaws were studied to understand how they reacted to interactions with a familiar animal caretaker. Studies show that Blue and Yellow Macaws demonstrated a significant amount of blushing frequently during mutual interactions with a caretaker. In another experiment, Jeffrey Mogil studied facial expression in mice in response to increments of increasing pain. He found that mice exhibited five recognizable facial expressions: orbital tightening, nose and cheek bulge, and changes in ear and whisker carriage.
;Gaze-following: Social animals use gaze-following as a form of communication through monitoring head and eye orientation in other mammals. Studies have been conducted on apes, monkeys, dogs, birds, wolves, and tortoises, and have focused on two different tasks: "follow another's gaze into distant space" and "follow another's gaze geometrically around a visual barrier, e.g., by repositioning themselves to follow a gaze cue when faced with a barrier blocking their view". A broad range of animals have been proven to exhibit the latter, however, only apes, dogs, wolves, and corvids have been able to follow another's gaze into distant space. Marmosets and ibis were unable to demonstrate "geometric gaze following". Researchers do not yet have a clear picture of the cognitive basis of gaze following, but developmental evidence indicates that "simple" gaze following and "geometric" gaze following probably rely on different cognitive mechanisms.
;Colour change: Colour change can be separated into changes that occur during growth and development, and those triggered by mood, social context, or abiotic factors such as temperature. The latter are seen in many taxa. Some cephalopods, such as the octopus and the cuttlefish, have specialized skin cells that can change the apparent colour, opacity, and reflectiveness of their skin. In addition to their use for camouflage, rapid changes in skin colour are used while hunting and in courtship rituals. Cuttlefish may display two entirely different signals simultaneously from opposite sides of their body. When a male cuttlefish courts a female in the presence of other males, he displays a male pattern facing the female and a female pattern facing away, to deceive other males. Some colour signals occur in cycles. For example, when a female olive baboon begins to ovulate, her anogenital area swells and turns a bright red/pink. This signals to males that she is ready to mate. Humboldt squid are bioluminescent and thus capable of communicating visually in dark ocean environments.
;Bioluminescent communication: Communication by the production of light occurs commonly in vertebrates and invertebrates in the oceans, particularly at depths. Two well-known forms of land bioluminescence occur in fireflies and glow worms. Other insects, insect larvae, annelids, arachnids, and even species of fungi possess bioluminescent abilities. Some bioluminescent animals produce the light themselves, whereas others have a symbiotic relationship with bioluminescent bacteria. Animals exhibit bioluminescent light to lure in prey, attract a mate, or protect themselves from potential predators.
Signaling
There are many different types of signals that animals use to differentiate their position of direction, location, and distance. Practitioners study the issues of animal position by geometric viewings. Environmental and social influences are indicators of geometric viewings. Animals rely on signals called electrolocating and echolocating; they use sensory senses in order to navigate and find prey. Signals are used as a form of commutation through the environment. Active signals or other types of signals influence receivers behavior and signals move quicker in distance to reach receivers.Auditory
Many animals communicate through vocalization. Vocal communication serves many purposes, including mating rituals, warning calls, conveying location of food sources, and social learning. In a number of species, males perform calls during mating rituals as a form of competition against other males and to signal to females. Examples include frogs, hammer-headed bats, red deer, humpback whales, elephant seals, and songbirds. Other instances of vocal communication include the alarm calls of the Campbell monkey, the territorial calls of gibbons, and the use of frequency in greater spear-nosed bats to distinguish between groups. The vervet monkey gives a distinct alarm call for each of its four different predators, and the reactions of other monkeys vary appropriately according to the call. For example, if an alarm call signals a python, the monkeys climb into the trees, whereas the "eagle" alarm causes monkeys to seek a hiding place on the ground. Prairie dogs also use complex calls that signal predator differences. According to Con Slobodchikoff and others, prairie dog calls communicate the type, size, and speed of an approaching predator. Whale vocalizations have been found to have different dialects based on social learning. Mammalian acoustic culture was first discovered in southern resident orcas in 1978.Not all animals use vocalization as a means of auditory communication. Many arthropods rub specialized body parts together to produce sound. This is known as stridulation. Crickets and grasshoppers are well known for this, but many others use stridulation as well, including crustaceans, spiders, scorpions, wasps, ants, beetles, butterflies, moths, millipedes, and centipedes. Another means of auditory communication is the vibration of swim bladders in bony fish. The structure of swim bladders and the attached sonic muscles varies greatly across bony fish families, resulting in a wide variety of sounds. Striking body parts together can also produce auditory signals. A well-known example of this is the tail tip vibration of rattlesnakes as a warning signal. Other examples include bill clacking in birds, wing clapping in manakin courtship displays, and chest beating in gorillas.
Burrowing animal species are known to whistle to communicate threats, and sometimes mood. Species such as the marmot species, including the groundhog, and the alpine marmot show this trait. Whistling is used by animals such as prairie dogs to communicate threats, with prairie dogs having one of the most complex communication systems in the animal kingdom. Prairie dogs are able to communicate an animal's speed, shape, size, species, and for humans specific attire and if the human is carrying a gun. This method of communication is usually done by having a sentry stand on two feet and surveying for potential threats while the rest of the pack finds food. Once a threat has been identified the sentry sounds a whistle alarm, at which point the pack retreats to their burrows. The intensity of the threat is usually determined by how long the sentry whistles. The sentry continues to whistle the alarm until the entirety of the pack has gone to safety, at which point the sentry returns to the burrow.
Olfactory
Despite being the oldest method of communication, chemical communication is one of the least understood forms due in part to the sheer abundance of chemicals in our environment and the difficulty of detecting and measuring all the chemicals in a sample. The ability to detect chemicals in the environment serves many functions, a crucial one being the detection of food, a function that first arose in single-celled organisms living in the oceans during the early days of life on Earth. As this function evolved, organisms began to differentiate between chemical compounds emanating from resources, conspecifics, and heterospecifics.For instance, a small minnow species may do well to avoid habitat with a detectable concentration of chemical cues associated with a predator species such as a northern pike. Minnows with the ability to perceive the presence of predators before they are close enough to be seen and then respond with adaptive behavior are more likely to survive and reproduce. Atlantic salmon go a step further than detecting a predator's cue: when an individual is damaged by a predator, it releases a chemical cue to its conspecifics. As has also been observed in other species, acidification and changes in pH physically disrupt these chemical cues, which has various implications for animal behavior.
Scent marking and scent rubbing are common forms of olfactory communication in mammals. An example of scent rubbing by an animal can be seen from bears, bears do this as a way to mark territory or let others know they are there and to stay away. Wolves scent-mark frequently during the breeding season.