Visual ;
Gestures: Most animals understand communication through a visual
display of distinctive body parts or bodily movements. Animals 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[ing] another's gaze into distant space" and "follow[ing] 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 (ravens) 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. 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 (e.g.,
angler fish). 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. (See also:
List of bioluminescent organisms)
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 s can serve as alarms or keep members of a
flock in contact, while the longer and more complex
bird songs are associated with
courtship and mating. 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. 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, (sometimes describing the threat) 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 in a tiger , an example of interspecific communication using body posture and olfaction. 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 (
bacteria) living in the oceans during the early days of life on Earth. Minnows with the ability to perceive the presence of predators before they are close enough to be seen and then respond with adaptive behavior (such as hiding) 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.
Electric Electrocommunication is a rare form of communication in animals. It is seen primarily in aquatic animals, though some land mammals, notably the
platypus and
echidnas, sense electric fields that might be used for communication.
Weakly electric fishes provide an example of electrocommunication, together with
electrolocation. These fish use an electric organ to generate an electric field, which is detected by
electroreceptors. Differences in the waveform and frequency of changes in the field convey information on species, sex, and identity. These electric signals can be generated in response to hormones, circadian rhythms, and interactions with other fish. They can also serve to mediate social hierarchy amongst species that have a social order. Some predators, such as sharks and rays, are able to eavesdrop on these electrogenic fish through passive electroreception.
Touch :
For more on the mechanism for touch, see Somatosensory system and Mechanoreceptors Touch is a key factor in many social interactions. Examples include: ;Fighting: In a fight, touch may be used to challenge an opponent and to coordinate movements during the fight. It may also be used by the loser to indicate submission. ;Mating: Mammals often initiate mating by grooming, stroking or rubbing against each other. This provides the opportunity to apply chemical signals and to assess those excreted by the potential mate. Touch may also announce the intention of the male to mount the female, as when a male kangaroo grabs the tail of a female. During mating, touch stimuli are important for pair positioning, coordination and genital stimulation. ;Social integration: Touch is widely used for social integration, a use that is typified by the social grooming of one animal by another. Social grooming has several functions; it removes parasites and debris from the groomed animal, it reaffirms the social bond or hierarchical relationship between the animals, and it gives the groomer an opportunity to examine
olfactory cues on the groomed individual, perhaps adding additional ones. This behaviour has been observed in social insects, birds and mammals. ;Foraging: Some ant species recruit fellow workers to new food finds by first tapping them with their antennae and forelegs, then leading them to the food source while keeping physical contact. "Patrollers" leave the nest to check for danger nearby and return to recruit "foragers" by making physical contact. Another example of this is the
waggle dance of honey bees. Some organisms live in constant contact in a colony, for example colonial corals. When individuals are linked tightly in this way an entire colony can react on the aversive or alarm movements made by only a few individuals. In several herbivorous insect nymphs and larvae, aggregations where there is prolonged contact play a major role in group coordination. These aggregations may take the form of a procession or a rosette.
Seismic Seismic communication is the exchange of information using self-generated vibrational signals transmitted via a substrate such as the soil, water, spider webs, plant stems, or a blade of grass. This form of communication has several advantages, for example it can be sent regardless of light and noise levels, and it usually has a short range and short persistence, which may reduce the danger of detection by predators. The use of seismic communication is found in many taxa, including frogs, kangaroo rats, mole rats, bees, nematode worms, and others. Tetrapods usually make seismic waves by drumming on the ground with a body part, a signal that is sensed by the
sacculus of the receiver. The sacculus is an organ in the inner ear containing a membranous sac that is used for balance, but can also detect seismic waves in animals that use this form of communication. Vibrations may be combined with other sorts of communication.
Thermal Several snakes have the ability to sense
infrared thermal radiation, which allows these
reptiles to derive thermal images from the radiant heat emitted by predators or prey at
wavelengths between 5 and 30
μm. The accuracy of this sense is such that a blind
rattlesnake can target its strike to the vulnerable body parts of a prey animal. It was previously thought that the pit organs evolved primarily as prey detectors, but it is now believed that they may also be used to control body temperature. The facial pits enabling thermoregulation underwent
parallel evolution in
pitvipers and some
boas and
pythons, having evolved once in pitvipers and multiple times in boas and pythons. The
electrophysiology of the structure is similar between lineages, but it differs in gross structure
anatomy. Most superficially, pitvipers possess one large pit organ on either side of the head, between the eye and the nostril (
loreal pit), while boas and pythons have three or more comparatively smaller pits lining the upper and sometimes the lower lip, in or between the scales. Those of the pitvipers are the more advanced, having a suspended sensory membrane as opposed to a simple pit structure. Within the family
Viperidae, the pit organ is seen only in the subfamily
Crotalinae: the pitvipers. Despite the detection of IR radiation, the pits' IR mechanism is dissimilar to photoreceptors; while photoreceptors detect light via photochemical reactions, the protein in the facial pits of snakes is a temperature sensitive ion channel. It senses infrared signals through a mechanism involving warming of the pit organ, rather than chemical reaction to light. This is consistent with the thin pit membrane, which allows incoming IR radiation to quickly and precisely warm a given ion channel and trigger a nerve impulse, as well as vascularize the pit membrane to rapidly cool the ion channel back to its original "resting" or "inactive" temperature. Vampire bats are the only mammals that feed exclusively on blood. The IR sense enables Desmodus to localize
homeothermic animals such as cattle and horses within a range of about 10 to 15 cm. This
infrared perception may be used in detecting regions of maximal blood flow on targeted prey. ==Autocommunication==