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

Abstract

Mirror-guided self-inspection is seen as a cognitive hallmark purportedly indicating the existence of self-recognition. Only a few species of great apes have been reported to pass a standard mark test for mirror self-recognition in which animals attempt to touch a mark. In addition, evidence for passing the mark test was also reported for Asian elephants, two species of corvids, and a species of cleaner fish. Mirror self-recognition has also been claimed for bottlenose dolphins, using exposure of marked areas to a mirror as evidence. However, what counts as self-directed behaviour to see the mark and what does not has been debated. To avoid this problem, we marked the areas around both eyes of the animals at the same time, one with visible and the other with transparent dye to control for haptic cues. This allowed the animal to see the mark easily and us to investigate what side was exposed to the mirror as an indicator for mark observation. We found that the animals actively chose to inspect their visibly marked side while they did not show an increased interest in a marked conspecific in the pool. These results demonstrate that dolphins use the mirror to inspect their marks and, therefore, likely recognise a distinction between self and others.

Identity and the Brain: The Biological Basis of Our Self

“…Certain animals, particularly higher primates and dolphins, have been shown to have evidence of self‐consciousness. A dolphin will spend more time looking at itself in the mirror if certain marks are placed on its head (Loth, Güntürkün and von Fersen 2022). Of course, the communication barrier is a challenging problem, but it might be possible to observe whether animals appear to have consciousness in some form as better methodologies are developed.…”

Minding the Minds: A Primer on Cognitive Challenge for Marine Mammals in Human Care

“…Marine mammals have lived in zoological facilities such as zoos, aquaria, and marine mammal parks for more than the past century. During that time, studies have suggested that at least some of these species possess complex cognitive and communicative abilities, including imitation [ 1 , 2 , 3 , 4 ]; metacognition [ 5 ]; mirror self-recognition [ 6 ]; vocally-coordinated cooperation [ 7 ]; the ability to learn symbols and basic syntax [ 8 , 9 , 10 ]; and decades-long memory [ 11 , 12 ]. Over this same time period, thanks to advances in veterinary knowledge and husbandry care, there has been significant and ongoing improvement in the physical welfare of these animals, as evidenced by increases in their health, longevity, and breeding success [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ].…”

Geckos differentiate self from other using both skin and faecal chemicals: evidence towards self-recognition?

“…Third, a mark has to be applied in a spot that can be seen without the use of the mirror to confirm the subjects’ motivation to remove marks in general (Gallup and Anderson 2018 ). Humans, most great apes, elephants, dolphins and cleaner fish show MSR (Gallup 1970 ; Gallup et al 2011 ; Kohda et al 2019 ; 2022 ; Loth et al 2022 ; Plotnik et al 2006 ; Reiss and Marino 2001 ). The evidence from species other than humans and great apes has, however, led to controversial discussion (Gallup and Anderson 2018 ; 2020 ).…”