A comparative study of mirror self-recognition in three corvid species

Abstract

Mirror self-recognition (MSR) assessed by the Mark Test has been the staple test for the study of animal self-awareness. When tested in this paradigm, corvid species return discrepant results, with only the Eurasian magpies and the Indian house crow successfully passing the test so far, whereas multiple other corvid species fail. The lack of replicability of these positive results and the large divergence in applied methodologies calls into question whether the observed differences are in fact phylogenetic or methodological, and, if so, which factors facilitate the expression of MSR in some corvids. In this study, we (1) present new results on the self-recognition abilities of common ravens, (2) replicate results of azure-winged magpies, and (3) compare the mirror responses and performances in the mark test of these two corvid species with a third corvid species: carrion crows, previously tested following the same experimental procedure. Our results show interspecies differences in the approach of and the response to the mirror during the mirror exposure phase of the experiment as well as in the subsequent mark test. However, the performances of these species in the Mark Test do not provide any evidence for their ability of self-recognition. Our results add to the ongoing discussion about the convergent evolution of MSR and we advocate for consistent methodologies and procedures in comparing this ability across species to advance this discussion.

Mirror stimulation in Eurasian jays (Garrulus glandarius)

“…This is quite interesting because these corvid species all failed to pass the classic mark-test and, more importantly, the behaviors often considered as indicators of the ability to pass the mark-test (exploratory behavior, contingent behavior and self-exploration) were limited both in the occurrences displayed, as well as in the number of individuals displaying them ( Brecht, Müller & Nieder, 2020 ; Vanhooland, Bugnyar & Massen, 2020 ; Wang et al, 2020 ). Our results indicate that neophobia can posit a challenge for the jays, and most likely to other corvids as well, to approach and explore the mirror, appreciate its reflective property, and use it to explore parts of their body otherwise not visible ( Vanhooland et al, 2023 ).…”

“…Therefore, the time in direct view of the mirror was definitely less compared to when birds were tested in a more confined testing compartment and forced to face the mirror. The effective time in front of the mirror has also been proposed to explain the overall delayed occurrences of contingent behavior in ravens or a lack of interest towards the mirror in azure-winged magpies ( Vanhooland, Bugnyar & Massen, 2020 ; Vanhooland et al, 2023 ). On the other hand, some suggestive evidence of MSR has been proposed to have been found in mirror-naïve Clark’s nutcrackers presented with a social caching task in a small compartment (in which they were in view of a mirror most or all of the time; Clary & Kelly, 2016 ), as well as in another mirror-related cache-protection study involving California scrub-jays without previous mirror exposure ( Dally, Emery & Clayton, 2010 ).…”

“…African grey parrots have been successful at mirror-mediated object discrimination, mirror-triggered search, and mirror-guided spatial locating ( Pepperberg et al, 1995 ), New Caledonian crows solved a mirror-guided spatial locating task ( Medina et al, 2011 ) and azure-winged magpies failed a mirror-guided spatial locating task ( Wang et al, 2020 ), but the mirrored image of a treat did trigger search efforts. Generally, avian species exposed to mirror-image stimulation react to their reflected image socially, but a few of the species did not show social responses (or these decreased over habituation), and possible contingency checking occurred ( Prior, Schwarz & Güntürkün, 2008 ; Van Buuren et al, 2018 ; Vanhooland, Bugnyar & Massen, 2020 ; Buniyaadi, Taufique & Kumar, 2020 ; Vanhooland et al, 2023 ). Instances of self-examination are extremely rare, but one parrot may have done so by examining the bottom of its foot in the mirror and real life simultaneously ( Pepperberg et al, 1995 ).…”

“…Three studies claim to find evidence of MSR in corvids ( Prior, Schwarz & Güntürkün, 2008 ; Clary & Kelly, 2016 ; Buniyaadi, Taufique & Kumar, 2020 ). However, the claims about MSR in birds are highly debated, with later studies failing to replicate initial findings ( Soler et al, 2020 ; Parishar, Mohapatra & Iyengar, 2021 ), and other studies reporting negative results (carrion and hooded crows, Vanhooland, Bugnyar & Massen, 2020 ; Brecht, Müller & Nieder, 2020 ; azure-winged magpies, Wang et al, 2020 ; great tits, Kraft et al, 2017 ; keas and Goffin’s cockatoos, Van Buuren et al, 2018 ; ravens, Baciadonna et al, 2022 ; Vanhooland et al, 2023 ). In the studies in which a mark-test was conducted, birds were also, as would be expected, presented with a mirror stimulation test in which their behaviors towards the mirror itself were recorded.…”

Could theropod dinosaurs have evolved to a human level of intelligence?

“…Among nonhuman mammals, it has been consistently seen in individual chimpanzees, orangutans, and dolphins, and in Asian elephants, gorillas, and gibbons mirror‐guided self‐recognition was seen in some studies and individuals but not others (Emery & Clayton, 2004b; Prior et al., 2008; Ristau, 2013). By contrast, among avian species thought to parallel apes in their intelligence, common ravens, azure‐winged magpies, carrion crows, jungle crows, and African grey parrots have not shown mirror‐guided self‐recognition (Emery & Clayton, 2004b; Vanhooland et al., 2022; Wang et al., 2020), although such self‐recognition was reported in Indian crows (Parishar et al., 2021) and in three of five Eurasian magpies (a corvid) tested (Prior et al., 2008), but not in another study of a larger magpie cohort (Soler et al., 2020). Moreover, although crows mimic chimpanzees in tool use, some authors have shown that chimpanzees can be taught to communicate using human sign language (Gardner & Gardner, 1980), but there is no such evidence for language use by corvids, suggesting that while corvids may cognitively match chimpanzees in some regards, they do not do so in all regards.…”