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Scientists have been studying the behavioral ethos of nonhumans for a long time. Amongst various traits of nonhumans, the peculiarities of self-awareness have also been studied, but in a few species only. The literature reveals that Gallup Jr1 was the first to conduct such studies in 1970. To examine whether the particular nonhuman individuals, chimpanzees, in his case, possessed the capacity of self-recognition, Gallup Jr1 devised a novel technique using a mirror. Based on the ability of chimpanzees to recognize themselves as individuals through their mirror images and he named this technique the "Mirror Test".
In his original experiments, Gallup Jr identified four chimpanzees and after 2 days of isolation prior to the test, exposed them individually for 8 h on each of the 2 study days to their reflected images in a mirror. Following another 8 days-approximately 80 h-of prolonged exposure to their reflected images in the mirror, all the four chimpanzees, when marked with a red dye on a part of their body, which they could not directly see, attempted to touch the red marks on their own bodies after seeing their reflections in the mirror. It was interpreted as clear evidence that the chimpanzees possess the self-awareness trait, as they seemed to identify the individuals bearing the red marks, in the mirrors as being themselves. With this experiment, Gallup Jr. was able to show that chimpanzees possess the capacity for self-recognition.
Over the years, self-recognition through mirror-images has been reported as an emergent phenomenon in several studies on nonhuman species, including, amongst others, the great apes, bottlenose dolphins, Asian elephants, and most recently, a fish species-the cleaner wrasse2. The comprehensiveness of Gallup's mirror test has, however, often been challenged, especially with respect to animals that rely on sensory modalities other than vision to perceive themselves and their environment3.
In birds, self-awareness has been investigated successfully using the mirror test in pigeons4, magpies5, and Indian house crows6. Using the mirror-image technique, Epstein and his colleagues4 investigated the self-awareness trait in three pigeons through their ability to locate a spot on each of their body, which they could not see directly, following independent exposure and habituation to a mirror for ~15 h over a 10 day training period. The study of literature reveals that in all investigations, every individual bird, however, had to undergo a variety of prior laboratory experiences, similar to that of Gallup Jr.'s chimpanzees, and they all acquired repertoires similar to those of the experimental chimpanzees. It must be noted, however, that the ability of birds to generally recognize themselves visually in a mirror remains equivocal, with jackdaws7 and carrion crows8,9 having failed the mirror mark test10.
Mirror tests are often conducted under highly artificial laboratory settings, without knowledge of how individuals will react toward their reflection in the wild11. More generally, should a failure to recognize oneself or fail the mirror test necessarily mean that a particular nonhuman lacks self-awareness or the capacity to become the object of one's own attention12,13.
There are a few definitions of self-awareness. Henley equates awareness with self-reports indicating that an observer "consciously see" a stimulus14,15. We have considered 'self-awareness' as the ability of the animal to be intrinsically conscious of its surrounding environment and processes—the "turning inward" aspect of the self and its recursiveness16.
Penguins are ancient flightless birds found mostly in the Southern hemisphere. They are one of the few species surviving on earth for over 60 million years, having outlived even the dinosaurs. Over time, penguins evolved a suite of morphological, physiological, and behavioral features that make them arguably the most uniquely specialized of all extant birds. These adaptations have allowed penguins to colonize some of the most extreme environments on Earth17.
Amongst 17 species of penguins found worldwide, only seven species inhabit the Antarctica and sub-Antarctic islands, and of these, the Adélie penguin, Pygoscelis adeliae, is the most abundant18,19. They are social birds, with remarkable adaptive features, which include feeding, swimming, nesting, and breeding colonially in discrete homogeneous groups, but only in the ice-sea zones. The extreme climate of Antarctica necessitates a high level of cooperative behavior amongst these penguins-an essential prerequisite for the development and maintenance of rookeries-areas where penguins, seals, and some other species of animals or birds live or breed.
A study of literature revealed that no study has been done on finding self-awareness characteristics in penguins in Antarctica. This could be because of the presence of penguin colonies in remote and isolated places in Antarctica, coupled with its extremely cold environment (near the coast, the summer temperature may vary from 30 C to +10 C)20, and difficult snow-covered terrain.
In this study, possibly the first of its kind on any penguin species, we examined the responses and reactions of wild Adélie penguins Pygoscelis adeliae, both individually and as a group, to their self-images, generated in a mirror during several field experiments. Our investigations led us to tentatively suggest that Adélie penguins have the self-awareness characteristic (intrinsic quality). We argue that this self-awareness trait in penguins may play a critical role during their various colonial activities and social interactions in which individuals of this avian species are typically engaged.
This study is pioneering in reporting the presence of self-awareness trait in a non-human species in a natural ecosystem, without any acclimatization or prior training of test species. It is also the first study on penguins in the difficult, snow-covered, and barren terrain of the Antarctica region having extremely low temperatures, 30 C to +10 C. Here, not only proper care was ensured in handling the highly sensitive species but the prescribed 'Code of Conduct' was also strictly followed21.