Animal song is not a well-defined term in scientific literature, and the use of the more broadly defined term vocalizations is in more common use. Song generally consists of several successive vocal sounds incorporating multiple syllables. [1] Some sources distinguish between simpler vocalizations, termed “calls”, reserving the term “song” for more complex productions. [2] Song-like productions have been identified in several groups of animals, including cetaceans (whales and dolphins), avians (birds), anurans (frogs), and humans. Social transmission of song has been found in groups including birds and cetaceans.
Most mammalian species produce sound by passing air from the lungs across the larynx, vibrating the vocal folds. [3] Sound then enters the supralaryngeal vocal tract, which can be adjusted to produce various changes in sound output, providing refinement of vocalizations. [3] Although morphological differences between species affect production of sound, neural control is thought to be more essential factor in producing the variations within human speech and song compared to those of other mammals. [3] Cetacean vocalizations are an exception to this general mechanism. Toothed whales (Odontocetes) pass air through a system of air sacs and muscular phonic lips, which vibrate to produce audible vocalizations, thus serving the function of vocal folds in other mammals. [4] Sound vibrations are conveyed to an organ in the head called the melon, which can be changed in shape to control and direct vocalizations. [5] Unlike in humans and other mammals, toothed whales are able to recycle air used in vocal production, allowing whales to sing without releasing air. [4] Some cetaceans, such as humpback whales, sing continuously for hours. [6]
Like mammals, anurans possess a larynx and vocal folds, which are used to create vibrations in sound production. [3] However, frogs also use structures called vocal sacs, elastic membranes in the base of the mouth which inflate during sound production. [7] These sacs provide both amplification and fine-tuning of sounds, and also allow air to be pushed back into the lungs during vocalizations. [4] This allows air used in sound production to be recycled, and is thought to have evolved to increase song efficiency. [7] Increased efficiency of sound production is important, as some frogs may produce calls lasting for several hours during mating seasons. [7] The New River tree frog ( Trachycephalus hadroceps ), for example, spends hours producing up to 38,000 calls in a single night, which is made possible through the efficient recycling of air by the vocal sac. [7]
When birds inhale, air is passed from the mouth, through the trachea, which forks into two bronchii connecting to the lungs. [8] The primary vocal organ of birds is called the syrinx, which is located at the fork of the trachea, and is not present in mammals. [9] As air passes through the respiratory tract, the syrinx and the membranes within vibrate to produce sound. [10] Birds are capable of producing continuous song during both inhalation and exhalation, and may sing continuously for several minutes. [11] For example, the skylark ( Alauda arvensis ) is capable of producing non-stop song for up to one hour. [12] Some birds change their song characteristics during inhalation versus exhalation. The Brewer's sparrow ( Spizella breweri ) alternates between rapid trilling during exhalation interspersed with lower-rate trills during short inhalations. [13] The two halves of the syrinx connect to separate lungs, and can be controlled independently, allowing some birds to produce two separate notes simultaneously. [9]
Insects such as crickets (family Gryllidae) are well known for their ability to produce loud song, however the mechanism of sound production differs greatly from most other animals. Many insects generate sound by mechanical rubbing of body structures, a mechanism known as stridulation. [14] Orthopteran insects, including crickets and katydids (family Tettigoniidae), have been especially well-studied for sound production. These insects use scraper-like structures on one wing to sweep over file-structures on an opposing wing to create vibrations, producing a variety of trilling and chirping sounds. [15] [16] Locusts and other grasshoppers (suborder Caelifera) stridulate by rubbing hind legs against pegs on wing surfaces in an up and downward motion. [17] Cicadas (superfamily Cicadoidea) produce sound at much greater volumes than Orthopterans, relying on a pair of organs called tymbals on the base of the abdomen behind the wings. [18] [15] Muscle contraction rapidly deforms the tymbal membrane, emitting several different types of sounds. [15] Insects thus produce a variety of sounds, using various mechanisms distinct from other animals.
Vocalizations can play a wide variety of different roles. In groups such as anurans and birds, several distinct types of notes are incorporated to form songs, which are sung in different situations and serve distinct functions. [19] For example, many frogs may use trilling notes in mate attraction, but switch to different vocal patterns in aggressive territorial displays. [19] In some species, a single song incorporates several note types which serve different purposes, with one type of note eliciting responses from females, and another note of the same song responsible for warning competitor males of aggression. [19]
Vocalizations play an important role in the mating behaviour of many animals. In many groups (birds, frogs, crickets, whales etc.), song production is more common in males of the species, and is often used to attract females. [19] [20] [21]
Bird song is thought to have evolved through sexual selection. Female songbirds often assess potential mates using song, based on qualities such as high song output, complexity and difficulty of songs, as well as presence of local dialect. [22] Song output serves as a fitness indicator of males, since vocalizations require both energy and time to produce, and thus males capable of producing high song output for long durations may have higher fitness than less vocal males. [22] It is thought that song complexity may serve as an indicator of male fitness by providing an indication of successful brain development despite potential early-life stressors, such as lack of food. [22] Social transmission of songs allows for development of local dialects of song, and female songbirds also typically prefer to choose mates producing local song dialects. [22] One hypothesis for this phenomenon is that selecting local mates allows the female to choose genes specially adapted to suit local conditions. [22]
Frog song also plays a prominent role in courtship. In túngara frogs ( Engystomops pustulosus ), male frogs increase the complexity of their calls, adding additional note types when greater numbers of competitor males are present, which has been found to attract greater numbers of female frogs. [23] Some species change their courtship calls when females are especially nearby. In male glass frogs (Hyalinobatachium fleichmanni), a long frequency-modulated vocalization is produced upon noticing another nearby frog, but is changed to a short chirping song when a female approaches. [19] Several species (e.g. dendrobatid frogs ( Mannophryne trinitatis ), ornate frogs ( Cophixalus ornatus ), splendid poison frogs ( Dendrobates speciosus )), switch from long-range loud trilling sounds to short-range quieter chirps when females move closer, which is thought to allow mate attraction without alerting competitor males to female locations. [19]
Although highly complex song-like production has been identified in whales, the function is still somewhat elusive. It is thought to be involved in courtship behaviour and sexual selection, and singing behaviour becomes more common during the breeding season. [24]
Another major function of song output is to indicate aggression among males during breeding seasons. Both anurans and birds use singing in territorial displays to confer aggressive intent. [19] [22] For Eastern smooth frogs ( Geocrinia victoriana ), for example, courtship songs involve shorter notes to attract potential mates, and are followed by longer tones to repel males. [19] Frequency of sounds produced generally negatively correlates with body size both within and among species, and allows competing males to assess body size of vocalizing neighbouring frogs. [25] Male frogs typically approach higher frequency sounds more readily than lower frequencies, likely because the frog producing the sound is assessed to be a smaller, less dangerous competitor. [25]
In territorial birds, males increase song production rate when neighbouring males encroach on their territory. [22] In great tits ( Parus major ), nightingales ( Luscinia megarhynchos ), blackbirds ( Turdus merula ) and sparrows (family Passeridae), playing song recordings slows the rate at which males establish territories in an unoccupied region, suggesting these birds rely on song output in establishing territorial boundaries. [22] Experimentally muted Scott's seaside sparrow ( Ammodramus maritimus ) lose control of their territories to other males. [22] Thus, territorial birds often rely on song production to repel conspecific males.
Like the human voice, bird song typically contains sufficient individual variability to allow discrimination of individual vocal patterns by conspecifics. [26] Such discrimination is important to mate recognition of many monogamous species. Seabirds, for example, often use vocalization patterns to recognize their mate upon reunion during the breeding season. [27] In many colonial nesting birds, parent-offspring recognition is critical to allow parents to locate their own offspring upon return to nesting sites. [28] Cliff swallows ( Petrochelidon pyrrhonota ) have been demonstrated to preferentially respond to parental songs at a young age, providing a means of vocalization-based offspring recognition. [28]
Learned vocalizations have been identified in groups including whales, elephants, seals, and primates, however the most well-established examples of learned singing is in birds. [29] In many species, young birds learn songs from adult males of the same species, typically fathers. [30] This was first demonstrated in chaffinches ( Fringilla coelabs ). Chaffinches raised in social isolation develop abnormal songs, however playing recordings of chaffinch songs allows the young birds to learn their species-specific songs. [31] Song learning generally involves a sensitive learning period in early life, during which young birds must be exposed to song from tutor animals in order to develop normal singing as adults. [32] Song learning occurs in two stages: the sensory phase and the sensorimotor phase. During the sensory phase, birds memorize the song of a tutor animal, forming a template representation of the species-specific song. [32] The sensorimotor phase follows and may overlap with the sensory phase. During the sensorimotor phase, young birds initially produce variable, rambling versions of adult song, called subsong. [32] As learning progresses, the subsong is replaced with a more refined version containing elements of adult song, called plastic song. Finally, the song learning crystallizes into adult song. [33] For song learning to occur properly, young birds must be able to hear and refine their vocal productions, and birds deafened before the development of subsong do not learn to produce normal adult song. [34]
The sensitive period in which birds must be exposed to song tutoring varies across species, but typically occurs within the first year of life. [32] Birds in which song learning is limited to the initial sensitive period are referred to as closed-ended learners, whereas some birds (e.g. canaries; Serinus canaria ), continue to learn new songs later in life, and are called open-ended learners. [32] Some species of birds, such as the brown-headed cowbird ( Molothrus ater ), parasitize other bird species, laying their eggs in the nests of other birds such that the heterospecific bird raises the chicks. [35] Although most birds acquire song learning within the first year, brown-headed cowbirds have a delayed sensitive period, occurring approximately one year after hatching. [35] This may be an adaptation to prevent the young birds from learning the songs from the foreign bird species. Instead, the young birds have a year in which to find conspecifics, and learn their own species-specific song. [35]
Birds are generally predisposed to favour learning of conspecific songs, and will typically preferentially learn the song form conspecific animals rather than heterospecifics. [31] However, song learning is not completely restricted to within-species songs. If exposed to heterospecific birds of another species in absence of same-species birds, young birds will often adopt the song of the species to which it was exposed. [31] Although birds are capable of learning song production purely from audio recordings of birdsong, tutor-student interaction may be important in some species. For example, white-crowned sparrows ( Zonotrichia leucophrys ) preferentially learn the songs of song sparrows ( Melospiza melodia ) when exposed to recordings of white-crowned sparrows and live song sparrows. [36] In other words, the interactive nature of a live tutor seems to trump the familiarity of the recordings from conspecifics.
While vertical transmission (parent-offspring) is a common element of song learning, horizontal transmission among animals of the same generation can also occur. [37] Male humpback whales produce various songs over their lifetime, which are learned from other males in the population. Males in a population conform to produce the same mating song, consisting of a highly stereotyped vocal display involved in mate attraction. [21] The cultural transmission of these songs has been found to occur across great geographic distances over years, with one study noting song transmission across the western and central South Pacific Ocean populations over an 11-year period. [21]
Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with, and compete with members of the same sex for access to members of the opposite sex. These two forms of selection mean that some individuals have greater reproductive success than others within a population, for example because they are more attractive or prefer more attractive partners to produce offspring. Successful males benefit from frequent mating and monopolizing access to one or more fertile females. Females can maximise the return on the energy they invest in reproduction by selecting and mating with the best males.
Bird vocalization includes both bird calls and bird songs. In non-technical use, bird songs are the bird sounds that are melodious to the human ear. In ornithology and birding, songs are distinguished by function from calls.
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 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.
Whales use a variety of sounds for communication and sensation. The mechanisms used to produce sound vary from one family of cetaceans to another. Marine mammals, including whales, dolphins, and porpoises, are much more dependent on sound than land mammals due to the limited effectiveness of other senses in water. Sight is less effective for marine mammals because of the particulate way in which the ocean scatters light. Smell is also limited, as molecules diffuse more slowly in water than in air, which makes smelling less effective. However, the speed of sound is roughly four times greater in water than in the atmosphere at sea level. As sea mammals are so dependent on hearing to communicate and feed, environmentalists and cetologists are concerned that they are being harmed by the increased ambient noise in the world's oceans caused by ships, sonar and marine seismic surveys.
Zoomusicology is the study of the musical aspects of sound and communication as produced and perceived by animals. It is a field of musicology and zoology, and is a type of zoosemiotics. Zoomusicology as a field dates to François-Bernard Mâche's 1983 book Music, Myth, and Nature, or the Dolphins of Arion, and has been developed more recently by scholars such as Dario Martinelli, David Rothenberg, Hollis Taylor, David Teie, and Emily Doolittle.
The banded penguins are penguins that belong to the genus Spheniscus. There are four living species, all with similar banded plumage patterns. They are sometimes also known as "jack-ass penguins" due to their loud locator calls sounding similar to a donkey braying. Common traits include a band of black that runs around their bodies bordering their black dorsal coloring, black beaks with a small vertical white band, distinct spots on their bellies, and a small patch of unfeathered or thinly feathered skin around their eyes and underdeveloped fluff sack that can be either white or pink. All members of this genus lay eggs and raise their young in nests situated in burrows or natural depressions in the earth.
Display behaviour is a set of ritualized behaviours that enable an animal to communicate to other animals about specific stimuli. Such ritualized behaviours can be visual, but many animals depend on a mixture of visual, audio, tactical and chemical signals. Evolution has tailored these stereotyped behaviours to allow animals to communicate both conspecifically and interspecifically which allows for a broader connection in different niches in an ecosystem. It is connected to sexual selection and survival of the species in various ways. Typically, display behaviour is used for courtship between two animals and to signal to the female that a viable male is ready to mate. In other instances, species may make territorial displays, in order to preserve a foraging or hunting territory for its family or group. A third form is exhibited by tournament species in which males will fight in order to gain the 'right' to breed. Animals from a broad range of evolutionary hierarchies avail of display behaviours - from invertebrates such as the simple jumping spider to the more complex vertebrates like the harbour seal.
Animal culture can be defined as the ability of non-human animals to learn and transmit behaviors through processes of social or cultural learning. Culture is increasingly seen as a process, involving the social transmittance of behavior among peers and between generations. It can involve the transmission of novel behaviors or regional variations that are independent of genetic or ecological factors.
The Túngara frog is a species of frog in the family Leptodactylidae. It is a small nocturnal terrestrial frog found in Mexico, Central America, and the northeastern regions of South America.
A courtship display is a set of display behaviors in which an animal, usually a male, attempts to attract a mate; the mate exercises choice, so sexual selection acts on the display. These behaviors often include ritualized movement ("dances"), vocalizations, mechanical sound production, or displays of beauty, strength, or agonistic ability.
Vocal learning is the ability to modify acoustic and syntactic sounds, acquire new sounds via imitation, and produce vocalizations. "Vocalizations" in this case refers only to sounds generated by the vocal organ as opposed to by the lips, teeth, and tongue, which require substantially less motor control. A rare trait, vocal learning is a critical substrate for spoken language and has only been detected in eight animal groups despite the wide array of vocalizing species; these include humans, bats, cetaceans, pinnipeds, elephants, and three distantly related bird groups including songbirds, parrots, and hummingbirds. Vocal learning is distinct from auditory learning, or the ability to form memories of sounds heard, a relatively common trait which is present in all vertebrates tested. For example, dogs can be trained to understand the word "sit" even though the human word is not in its innate auditory repertoire. However, the dog cannot imitate and produce the word "sit" itself as vocal learners can.
A mating call is the auditory signal used by animals to attract mates. It can occur in males or females, but literature is abundantly favored toward researching mating calls in females. In addition, mating calls are often the subject of mate choice, in which the preferences of one gender for a certain type of mating call can drive sexual selection in a species. This can result in sympatric speciation of some animals, where two species diverge from each other while living in the same environment.
The dear enemy effect or dear enemy recognition is an ethological phenomenon in which two neighbouring territorial animals become less aggressive toward one another once territorial borders are well established. As territory owners become accustomed to their neighbours, they expend less time and energy on defensive behaviors directed toward one another. However, aggression toward unfamiliar neighbours remains the same. Some authors have suggested the dear enemy effect is territory residents displaying lower levels of aggression toward familiar neighbours compared to unfamiliar individuals who are non-territorial "floaters".
Seismic or vibrational communication is a process of conveying information through mechanical (seismic) vibrations of the substrate. The substrate may be the earth, a plant stem or leaf, the surface of a body of water, a spider's web, a honeycomb, or any of the myriad types of soil substrates. Seismic cues are generally conveyed by surface Rayleigh or bending waves generated through vibrations on the substrate, or acoustical waves that couple with the substrate. Vibrational communication is an ancient sensory modality and it is widespread in the animal kingdom where it has evolved several times independently. It has been reported in mammals, birds, reptiles, amphibians, insects, arachnids, crustaceans and nematode worms. Vibrations and other communication channels are not necessarily mutually exclusive, but can be used in multi-modal communication.
Soundscape ecology is the study of the acoustic relationships between living organisms, human and other, and their environment, whether the organisms are marine or terrestrial. First appearing in the Handbook for Acoustic Ecology edited by Barry Truax, in 1978, the term has occasionally been used, sometimes interchangeably, with the term acoustic ecology. Soundscape ecologists also study the relationships between the three basic sources of sound that comprise the soundscape: those generated by organisms are referred to as the biophony; those from non-biological natural categories are classified as the geophony, and those produced by humans, the anthropophony.
Female copulatory vocalizations, also called female copulation calls or coital vocalizations, are produced by female primates, including human females, and female non-primates. Copulatory vocalizations usually occur during copulation and are hence related to sexual activity. Vocalizations that occur before intercourse, for the purpose of attracting mates, are known as mating calls.
Sexual selection in birds concerns how birds have evolved a variety of mating behaviors, with the peacock tail being perhaps the most famous example of sexual selection and the Fisherian runaway. Commonly occurring sexual dimorphisms such as size and color differences are energetically costly attributes that signal competitive breeding situations. Many types of avian sexual selection have been identified; intersexual selection, also known as female choice; and intrasexual competition, where individuals of the more abundant sex compete with each other for the privilege to mate. Sexually selected traits often evolve to become more pronounced in competitive breeding situations until the trait begins to limit the individual's fitness. Conflicts between an individual fitness and signaling adaptations ensure that sexually selected ornaments such as plumage coloration and courtship behavior are "honest" traits. Signals must be costly to ensure that only good-quality individuals can present these exaggerated sexual ornaments and behaviors.
Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts. Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations, with variations in depth of calls the speed of calls and other complex behaviours to attract mates. The fittest males will have the deepest croaks and the best territories, with females making their mate choices at least partly based on the males depth of croaking. This has led to sexual dimorphism, with females being larger than males in 90% of species, males in 10% and males fighting for groups of females.
Pollutant-induced abnormal behaviour refers to the abnormal behaviour induced by pollutants. Chemicals released into the natural environment by humans impact the behaviour of a wide variety of animals. The main culprits are endocrine-disrupting chemicals (EDCs), which mimic, block, or interfere with animal hormones. A new research field, integrative behavioural ecotoxicology, is emerging. However, chemical pollutants are not the only anthropogenic offenders. Noise and light pollution also induce abnormal behaviour.
Communication occurs when an animal produces a signal and uses it to influences the behaviour of another animal. A signal can be any behavioural, structural or physiological trait that has evolved specifically to carry information about the sender and/or the external environment and to stimulate the sensory system of the receiver to change their behaviour. A signal is different from a cue in that cues are informational traits that have not been selected for communication purposes. For example, if an alerted bird gives a warning call to a predator and causes the predator to give up the hunt, the bird is using the sound as a signal to communicate its awareness to the predator. On the other hand, if a rat forages in the leaves and makes a sound that attracts a predator, the sound itself is a cue and the interaction is not considered a communication attempt.