COMMUNICATION IN WHALES AND DOLPHINS (ECHOLOCATION) By olakunmi ogunrinde

Communication is simply the act of transferring information from one thing to another. Animal communication just like humans. Animals posses their own way of communicating and that can be said to be the transfer of information from one animal to one or more animals.

Different ways Whales and Dolphins communicate

To whales and dolphins, sound is very important as it could be used for hunting, navigating and communication. There are different ways they communicate like: clicks, whistles, body language and echolocation. My focus would be on echolocation

ECHOLOCATION

This is is a psychological process used for locating objects by reflected sounds in certain animals such as toothed whales, dolphins and bats.

How it works

These animals make sounds that project over a certain distance (varies with vertebrates). An echo is produced when the sound wave bounces off an objects or anything in range. The animals hear the echo and based on the frequency, they know which direction to move.

Evolution of echolocation in Whales

After detailed comparisons with living and fossil whales, it was discovered by Geisler and his colleagues who concluded that Cotylocara belonged to an extinct family of whales that split off from other whales at least 32 million years ago. The discovery, when viewed in the context of the entire toothed whale(whales that has teeth) family tree, implies that a rudimentary form of echolocation evolved in the common ancestor of Cotylocara and other toothed whales, between 35 and 32 million years ago. Once it evolved, the fossil record indicates that there was a progressive increase in size and complexity in the air sacs and muscles that controlled the sound generating apparatus in the face.Toothed whales, as well as baleen whales, were known to be descendants of land-dwelling mammals of the artiodactyl order. They are closely related to the hippopotamus, sharing a common ancestor that lived around 54 million years ago(mya). The primitive cetaceans, or archaeocetes, first took to the sea approximately 49 mya and became fully aquatic by 5–10 million years later. ("New fossil species: Origin of toothed whale echolocation" 2017)

The adaptation of echolocation occurred when toothed whales split apart from baleen whales, and distinguishes modern toothed whales from fully aquatic archaeocetes which happened around 34 mya.

How far the sounds can go

For whale, to feed in water over 150om deep, where light is absent, they produce unidirectional clicks of 235 dB re 1 μPa (underwater pressure unit: decibels with respect to 1 μPa), which is comparable to the sound of a powerful air rifle at a distance of 0.5 m. From the moment it dives, it begins to send out sound clicks, quickly locates prey and makes a beeline in that direction. The closer it gets, the more the interval between clicks decreases, i.e. the sounds become increasingly frequent. In dolphins, Echolocation is most effective at close to intermediate range, about 5 to 200 m (16–656 ft.) for targets 5 to 15 cm (2–6 in.) in length.

The distance that sound travels in the ocean also depends on the water temperature and pressure. Considering the fact that sound moves at much faster speed in water than in air, as the pressure continues to increase as ocean depth increases, temperature of the ocean decreases up to a certain point, after which it remains relatively stable.

How whales and dolphins communicate compared to other vertebrates

The sound is not produced through their mouth but through their blowhole(located on top the head). They use frequencies that are far beyond our hearing capabilities. Large whales can communicate over several hundred kilometres. Dolphins use higher frequencies which limits the distance. Whales also communicate by creating sounds and body language.

Relating to Bats

Most bats produce echolocation sounds by contracting their larynx (voice box). A few species, though, click their tongues. These sounds are generally emitted through the mouth, but Horseshoe bats (Rhinolophidae) and Old World leaf-nosed bats (Hipposideridae) emit their echolocation calls through their nostrils: there they have basal fleshy horseshoe or leaf-like structures that are well-adapted to function as megaphones

some bats can hear sounds up to 110 kHz in frequency. By emitting a series of often quite loud ultrasounds that either sweep from a high to low frequency or vary around a frequency, bats can distinguish objects and their insect prey and therefore avoid the object or catch the insect. The frequency range individual bat specie can produce depends on their environment and prey types.

Comparison of communication between whales and other vertebrate (Bat)

The environment can also affect the echolocation provided by both in sense that the whale is under water which is more secluded and has more advantage compared to bat which is in an open space in the air and so can easily be tampered with by climate change and other attributes in the air.

References

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Echolocation - Bat Conservation Trust. 2017. Available from http://www.bats.org.uk/pages/echolocation.html [accessed 1 March 2017].

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How do bats echolocate and how are they adapted to this activity?. 2017. Available from https://www.scientificamerican.com/article/how-do-bats-echolocate-an/ [accessed 15 March 2017].

How Far Away Can Sperm Whales Detect Their Prey? | Whales online. 2017. Available from http://baleinesendirect.org/en/how-far-away-can-sperm-whales-detect-their-prey/ [accessed 25 March 2017].

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National Marine Mammal Laboratory. 2017. Available from https://www.afsc.noaa.gov/nmml/education/cetaceans/cetaceaechol.php [accessed 30 March 2017].

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