Rapid self-recognition ability in the cleaner fish

TL;DR

Cleaner fish show rapid self-recognition in mirrors, suggesting they may be self-aware, similar to humans and some other animals.

Contribution

The study reveals rapid mirror self-recognition in cleaner fish and identifies behavioral differences before and after recognition.

Findings

Cleaner fish achieve mirror self-recognition rapidly, indicating possible self-awareness.

Behavioral differences were observed before and after mirror self-recognition in cleaner fish.

Self-recognition in cleaner fish shows parallels with human self-awareness processes.

Abstract

Whether animals are self-aware has important implications for our approaches to both animal cognition and animal welfare. A landmark moment in animal cognition research was when great apes passed the mark-test and demonstrated mirror self-recognition (MSR). Animals that pass the mark-test are capable of visually self-recognising and considered to be self-aware. Other taxa, including a fish, the cleaner wrasse (cleaner fish: Labroides dimidiatus) have also now passed the mark-test, forcing a rethink of the mental and neurological requirements for MSR. Previous research has largely focused on which species can pass the mark-test, rather than the processes underlying MSR. Here, we marked mirror-naïve cleaner fish with an ecologically relevant mark resembling an ectoparasite and then undertook detailed behavioural observations after exposure to a mirror. We found that cleaner fish achieve MSR rapidly, implying self-awareness prior to mirror exposure. By observing the exact timing of MSR in individuals, we could also report previously undocumented differences in pre- and post-MSR behaviours, including post-MSR exploratory behaviour of the mirror’s reflective properties. We find remarkable parallels between the processing of MSR in humans and cleaner fish, suggesting that some aspects of self-awareness are conserved across animal taxa.

The online version contains supplementary material available at 10.1038/s41598-025-25837-0.

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