Academic Review 2024

14 ST EDWARD’S, OXFORD

A female common bottlenose dolphin named Kelly, 44 years old, captive in Dolphin Cay in the Bahamas, shows the ease with which these cetaceans can learn. She was instructed to remove rubbish that unintentionally falls into her enclosure and give it to her trainers (Eveleth, 2018). She would be rewarded with fish. In time, she realised that the size of the rubbish did not affect the quantity or size of the fish reward. She then started to hoard the items she collected beneath a rock in her enclosure and hand the trainers the rubbish in smaller chunks. By returning more smaller bits of rubbish, she was echolocation. Echolocation serves two purposes: navigation and hunting prey (DolphinPlus, 2018). Without echolocation these species would not be able to hunt in such extraordinary ways as they do and would not be able to coordinate strategic attacks in pods. Echolocation is a major advantage for these organisms, acting as their sixth sense. This adaptation has been caused by the slight murkiness of seawater. Echolocation is ‘pneumatically driven’ (Illustra Media, 2016) by the compression of air. As air passes through the nasal passage it is compressed and then forced through the phonic lips, which vibrate. These vibrations create sound in the form of high and low frequency clicks (Illustra Media, 2016). The pressurised air collects in airsacs which, when full, push the air back down the nasal passage again. This reuse and re-compression of air allows for further Hunting and problem solving Both Orcanus orca and Tursiops truncatus use

rewarded with more fish (Eveleth, 2018). This skill of returning the rubbish was learnt, and then Kelly manipulated it to her benefit.

Both cetaceans communicate via the same mechanisms, via physical gestures and via

vocalisations. T. truncatus are known to have individual signature whistles compared to O. orca who share a dialect within a pod. O. orca have learnt to replicate the whistles of T. truncatus to lure them into a death trap, while T. truncatus have outsmarted their trainer in order to be rewarded with more food.

echolocation. The range of sounds generated by the phonic lips are absorbed and focused on the melon, an organ found in the forehead made of fatty tissues (DolphinPlus, 2018). The melon transmits these clicks into the surrounding water (see figure 1). These sonic waves bounce off specific targets and are received at the lower jaw at the acoustic window, passing through the innermost part of the ear where the signals travel along neurons to the brain where they are interpreted (DolphinPlus, 2018). Echolocation allows for a mental image of the object. Echolocation can be used to determine speed, density, internal anatomy, size, and location of prey (Illustra Media, 2016). This superpower can even allow these whales to detect the foetus inside a pregnant woman’s womb, in a way similar to ultrasound (Kankudti, 2013). This vivid example describes the remarkable level at which echolocation works, with the ability to see with sound.

monkey lips (phonic lips)

posteria bursa

Figure 1: A simplified diagram of the neuroanatomy, regarding components used for echolocation. (Whale and Dolphin Conservation, 2022).

blowhole

airsacs

anterior bursa

brain

melon

skull

maxilla

internal nares

mandible

auditory bulla (inner ear)

acoustic window (sound conducting tissue)