Wild recognition: conducting the mark test for mirror self-recognition on wild baboons

The distribution of self-awareness across species is important to understand, not only as a matter of scientific interest but also because of its implications for the ethical standing of non-human animals. The prevailing methodology for determining self-awareness is to test for visual self-recognition using mirror-image stimulation and a 'mark test'. However, most studies have involved very small sample sizes, omitted a control condition and been conducted on captive animals. Here, we designed and implemented the first controlled mark test in a wild setting, conducting the mark test using a laser pointer on a large (n = 51 individuals, 135 mark tests) sample of wild chacma baboons (Papio ursinus) in situ. Control tests showed that baboons were interested in the mark, but this interest decreased with age, and was greater in males and towards green (cf. red) marks. However, as predicted, subjects showed no evidence of visual self-recognition, which, given the control, cannot be attributed to a lack of motivation in the mark. Our study proposes a novel, controlled mark test in situ and contributes to the evidence that, without extensive training, non-hominid primates are not capable of full visual self-recognition.