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.Hill, P.S.M., (2008). Vibrational Communication in Animals. Harvard, Cambridge, London Vibrations and other communication channels are not necessarily mutually exclusive, but can be used in multi-modal communication.
Functions Communication requires a sender, a message, and a recipient, although neither the sender or receiver need be present or aware of the other's intent to communicate at the time of communication.
Intra-specific communication Vibrations can provide cues to conspecifics about specific behaviours being performed, predator warning and avoidance, herd or group maintenance, and courtship. The Middle East blind mole-rat (Spalax ehrenbergi) was the first mammal for which vibrational communication was documented. These fossorial rodents bang their head against the walls of their tunnels, which was initially interpreted as part of their tunnel building behaviour. It was eventually realised they generate temporally patterned vibrational signals for long-distance communication with neighbouring mole-rats. Footdrumming is used widely as a predator warning or defensive action. It is used primarily by fossorial or semi-fossorial rodents, but has also been recorded for spotted skunks (Spilogale putorius), deer (e.g. white-tailed deer Odocoileus virginianus), marsupials (e.g. tammar wallabies Macropus eugenii), rabbits (e.g. European rabbits Oryctolagus cuniculus) and elephant shrews (Macroscelididae).Randall, J.A., (2001). Evolution and function of drumming as communication in mammals. American Zoologist, 41: 1143–1156 Banner-tailed kangaroo rats (Dipodomys spectabilis) footdrum in the presence of snakes as a form of individual defense and parental care.Randall, M.D. and Matocq, J.A., (1997). Why do kangaroo rats (Dipodomys spectabilis) footdrum at snakes? Behavioural Ecology, 8: 404–413 Several studies have indicated intentional use of ground vibrations as a means of intra-specific communication during courtship among the Cape mole-rat (Georychus capensis).Narins, P.M., Reichman, O.J., Jarvis, J.U.M. and Lewis, E.R., (1992). Seismic signal transmission between burrows of the Cape mole-rat Georychus capensis. Journal of Comparative Physiology [A], 170: 13–22 Footdrumming has been reported to be involved in male-male competition where the dominant male indicates its resource holding potential by drumming, thus minimising physical contact with potential rivals. The Asian elephant (Elephas maximus) uses seismic communication in herd or group maintenanceO'Connell-Rodwell, C.E., Arnason, B. and Hart, L.A., (2000). Seismic properties of elephant vocalizations and locomotion. Journal of the Acoustical Society of America, 108: 3066–3072 and many social insects use seismic vibrations to coordinate the behaviour of group members, for example in cooperative foraging. Other insects use vibrational communication to search for and attract mates, like North American treehoppers, Enchenopa binotata. Males of this species use their abdomen to send vibrations through their host plant's stem. Females perceive these signals and respond to them to initiate a duet.Mcnett, G.D. and Cocroft, R.B. (2008). Host shifts favor vibrational signal divergence in Enchenopa binotata treehoppers. Behavioral Ecology. 19.3: 650–656.Wood, T.K., 1980. Intraspecific divergence in Enchenopa binotata Say (Homoptera: Membracidae) effected by host plant adaptation. Evolution, 34: 147–160Wood, T.K. & Guttman, S.I., 1982. Ecological and behavioural basis for reproductive isolation in the sympatric Enchenopa binotata complex (Homoptera: Membracidae). Evolution, 36: 233–242.
Inter-specific communication The banner-tailed kangaroo rat, (Dipodomys spectabilis), produces several complex footdrumming patterns in a number of different contexts, one of which is when it encounters a snake. The footdrumming may alert nearby offspring but most likely conveys that the rat is too alert for a successful attack, thus preventing the snake's predatory pursuit. Vibrations caused by stampeding animals may be sensed by other species to alert them to danger, thereby increasing the size of the stampede and reducing the risk of danger to an individual.
Eavesdropping Some animals use eavesdropping to either catch their prey or to avoid being caught by predators. Some snakes are able to perceive and react to substrate-borne vibrations. The vibrations are transmitted through the lower jaw, which is often rested on the ground and is connected with the inner ear. They also detect vibrations directly with receptors on their body surface. Studies on horned desert vipers (Cerastes cerastes) showed they strongly rely on vibrational cues for capturing prey. Localisation of the prey is probably aided by the two halves of the lower jaw being independent.
Vibrational cues can even indicate the life stage of prey thereby aiding optimal prey selection by predators, e.g. larval vibrations can be distinguished from those generated by pupae, or, adults from juveniles.Meyhöfer, R., Casas, J. and Dorn, S., (1994). Host location by a parasitoid using leafminer vibrations: characterizing the vibrational signals produced by the leafmining host. Physiological Entomology, 19: 349–359 Although some species can conceal or mask their movements, substrate-borne vibrations are generally more difficult to avoid producing than airborne vibrations. The common angle moth (Semiothisa aemulataria) caterpillar escapes predation by lowering itself to safety by a silk thread in response to substrate-borne vibrations produced by approaching predators.
Mimicry Several animals have learnt to capture prey species by mimicking the vibrational cues of their predators. Wood turtles (Clemmys insculpta),Kaufmann, J.H. (1986) Stomping for earthworms by wood turtles, Clemmys insculpta: a newly discovered foraging technique. Copeia, 1986: 1001–1004 European herring gulls (Larus argentatus),Tinbergen, N., (1960). The Herring Gull's World. New York: Basic Books, Inc. and humans have learnt to vibrate the ground causing earthworms to rise to the surface where they can be easily caught. It is believed that deliberately produced surface vibrations mimic the seismic cues of moles moving through the ground to prey on the worms; the worms respond to these naturally produced vibrations by emerging from their burrows and fleeing across the surface.
Other animals mimic the vibrational cues of prey, only to ambush the predator when it is lured towards the mimic. Assassin bugs (Stenolemus bituberus) hunt web-building spiders by invading the web and plucking the silk to generate vibrations that mimic prey of the spider. This lures the resident spider into striking range of the bug. Spiders from at least five different families routinely invade the webs of other spiders and lure them as prey with vibratory signals (e.g. Pholcus or 'daddy long-leg' spiders; salticid 'jumping' spiders from the genera Portia, Brettus, Cyrba and Gelotia).
Portia fimbriata jumping spiders lure female Euryattus species by mimicking male courtship vibrations.
Habitat sensing The wandering spider (Cupiennius salei) can discriminate vibrations created by rain, wind, prey, and potential mates. The creeping grasshopper can escape predation by this spider if it produces vibrations similar enough to those of wind.Barth, F.G., Bleckmann, H., Bohnenberger, J. and Seyfarth, E-A., (1988). Spiders of the genus Cupiennius Simon 1891 (Araneae, Ctenidae): II. On the vibratory environment of a wandering spider. Oecologia, 77:194–201 Thunderstorms and earthquakes produce vibrational cues; these may be used by elephants and birds to attract them to water or avoid earthquakes. Mole rats use reflected, self-generated seismic waves to detect and bypass underground obstacles – a form of "seismic echolocation".
However, this type of use is not considered communication in the strictest sense.
Production of vibrational cues Vibrational cues can be produced in three ways, through percussion (drumming) on the substrate, vibrations of the body or appendages transmitted to the substrate, or, acoustical waves that couple with the substrate. The strength of these cues depends mostly on the size and muscular power of the animal producing the signal.Markl, H., (1983). Vibrational communication. In: Neuroethology and Behavioral Physiology, edited by Huber, F. and Markl, H. Berlin: Springer-Verlag, pp. 332–353
Percussion Percussion, or drumming, can produce both short-and long-distance vibrational cues. Direct percussion of the substrate can yield a much stronger signal than an airborne vocalization that couples with the substrate, however, the strength of the percussive cue is related directly to the mass of the animal producing the vibration. Large size is often associated with greater source amplitudes, leading to a greater propagation range. A wide range of vertebrates perform drumming with some part of their body either on the surface or within burrows. Individuals bang heads, rap trunks or tails, stamp or drum with front feet, hind feet or teeth, thump a gular pouch, and basically employ available appendages to create vibrations on the substrates where they live.Hill, P.S.M., (2008). Vibrational Communication in Animals. Harvard, Cambridge, London Insects use percussion by drumming (or scraping) with the head, hind legs, fore legs, mid legs, wings, abdomen, gaster, antennae or maxillary palps.
Tremulation Tremulation is performed by a range of insects. This process involves rocking of the entire body with the subsequent vibrations being transferred through the legs to the substrate on which the insect is walking or standing.
Stridulation Insects and other arthropods stridulate by rubbing together two parts of the body. These are referred to generically as the stridulatory organs. Vibrations are transmitted to the substrate through the legs or body.
Tymbal vibrations Insects possess tymbals which are regions of the exoskeleton modified to form a complex membrane with thin, membranous portions and thickened "ribs". These membranes vibrate rapidly, producing audible sound and vibrations that are transmitted to the substrate.
Acoustically coupled