How do you reach out to your close ones to inform them about your feelings or to provide them with a useful piece of information? You’d call out to them, right?
And your tone isn’t the same when you’re happy as compared to when you’re sad.
Similar is the case with our animal friends. Apart from visual, olfactory, chemical, and tactile means of communication, sounds play an instrumental role in their communication, ranging from hunting its prey and escaping predators to attracting mates and navigating through the darkness.
In the two parts of the articles on animal sounds, we’ll delve into the acoustics of our animal friends and learn some intriguing and amazing features about how they utilise their abilities to serve various purposes.
Mammals like the bats, whales and the dolphins and others like the nocturnal oilbird have the amazing ability to determine the location of objects using reflected sound, which allows them to move around in pitch darkness, so they can navigate, hunt, identify friends and enemies, and avoid obstacles. This is called echolocation.
BATS
Of the 900 species of bats, most of them make echolocating sounds in their larynxes and emit them through their mouths. Fortunately, they are too high-pitched for humans to hear. In terms of loudness, bats emit calls as low as 50 dB and as high as 140 decibels, as loud as a jet engine 30m away!
Their external ears are designed to aid in the reception and funneling of echoes and sounds emitted from prey. Also, their ears and brain cells are specially tuned to the frequencies of the sounds they emit and the echoes that result in a concentration of receptor cells in their inner ear making bats extremely sensitive to frequency changes. To avoid being deafened by its own calls, its middle ear muscle (called the stapedius) contracts to separate the malleus, incus, and stapes just before calling, and reduces the hearing sensitivity, restoring its hearing a split second later to listen for echoes.
Amazing!!! Isn’t it?
DOLPHINS AND WHALES
Like humans, dolphins and whales are social creatures, typically found in pods, swimming, and hunting alongside other members.
Dolphin sounds have a whole range of frequencies, volumes, and patterns, including trills, clicks, buzzing, and squeaking. One very unique dolphin form of communication is the whistle. Each individual appears to have a “signature” whistle which is uniquely theirs and used to identify them. From birth, a mother dolphin whistles her own pattern continuously to her baby, perhaps to help him memorise her whistle. Dolphins have also been observed copying the whistles of their fellow friends too! Researchers often observe dolphins “chattering” and being answered by another dolphin, indicating they are engaged in some sort of dialogue.
Echolocation in dolphins is so finely honed that they can tell the difference between a ping-pong ball and golf ball by evaluating the density of the object. A 2010 study discovered that bats and dolphins have identical mutations of ‘Prestin’, a genetic protein affecting hearing sensitivity, making a strong case for convergent evolution of echolocation in bats and dolphins.
The sounds are made by squeezing air through nasal passages near the blowhole. These sound waves then pass into the forehead, where a big blob of fat called the melon focuses them into a beam. The sound waves reflect off the object back to the dolphin, specifically to a highly evolved, fat-rich area in a dolphin's lower jaw. Transmission of this acoustic information from the jaw to the middle ear to the brain allows the dolphin to rapidly interpret and process the information.
The whales mainly produce 3 types of sounds-- clicks, whistles, and pulsed calls.
Clicks are mainly produced by Toothed whales. They help in navigation and identifying physical surroundings by echolocation. Clicks can even help to differentiate between friendly creatures and predators.
Whistles and Pulsed calls are used during social activities.
Differing vocal “dialects” have been found to exist between different pods within the same whale population, suggesting that whales can differentiate between whales within their pods and strangers.
Baleen whales use low-frequency sounds, and these can be heard over long distances.
Some species such as the humpback and blue whale produce melodic tunes that are referred to by scientists as whale songs.
Whales and dolphins also use spy-hopping to keep them alert of their surroundings or use their tails and fins to make loud slapping noises on the surface of the water(tail slapping) to show aggression or warn other members of potential threats. Stay tuned for more.