The Dolphin in the Mirror – A Familiar Face?

Abstract

We suggest how a basic physics problem becomes much richer when researchers of various disciplines converse. Our discussion explores Snell’s window from the perspective of what a dolphin might see. An aperture, Snell’s window, allows light to travel through the air-water interface. Outside this window, there is total reflection from under the water-air interface. Dolphins see through the aperture to follow our movements above the water’s surface. When dolphins look outside the window, can they see their own reflections from under the water-air interface?

“Cognition in marine mammals: the strength of flexibility in adapting to marine life”

“…According to the new study (Loth et al 2022 ), bottlenose dolphins can use mirrors for self-inspection; nevertheless it is still hard to assess whether mirror-experiments can be interpreted regarding self-awareness (see Delfour 2006 ; Harley 2013 ). However, the authors’ observation that dolphins’ familiarity with natural reflecting surfaces such as the water’s surface (in line with Dibble et al 2017 )—one of their experimental animals seemed to have used the water surface instead of the artificial mirror to control its eye region during marking sessions—illustrates that specifics of the underwater environment, such as the presence of reflecting surfaces, may foster varying utilization of perceptual skills and different cognitive mechanisms related to the processing of stimulus representation and problem solving.…”

Through the looking glass: how do marked dolphins use mirrors and what does it mean?

“…This is true both for the captive as well as the natural environment of dolphins, so that all dolphins have access to reflecting surfaces and potential experience with their own mirrored image. However, when looking upwards to the water surface, dolphins will likely see a clear cone of light with a width of about 98° while everything around this manhole will be reflected like in a mirror (Dibble et al ( 2017 ). Thus, dolphins will not be able to see their head while approaching a flat air–water interface, but could undoubtedly see reflections of their posterior body as well as other dolphins that swim along.…”

“…Dolphins in zoos often have windows in their environment and the illumination of the tank with a dark surrounding make these good reflectors. Furthermore, dolphins are continuously faced with the reflective water surface when approaching it to breathe (Dibble et al 2017 ). Thus, these animals are likely to have a lot more experience with reflections than most other animals tested in these paradigms.…”

Through a glass darkly? Divergent reactions of eight Lake Tanganyika cichlid species towards their mirror image in their natural environment

“…These laboratory shortcomings call for careful verification of the explanatory value of mirror tests in a natural context. In the wild, the occasions where animals might be confronted with their mirror image are limited either to reflections in water surfaces (de Waal, 2019), though this is physically restricted to body parts not containing the head region in aquatic organism (Dibble et al, 2017), or to human‐made reflecting devices like polished metal or glass surfaces. Hence, most knowledge about how animals react when approaching their mirror image in the wild is derived from a limited number of species (de Waal, 2019).…”