Supplementary material from "Kangaroos display gazing and gaze alternations during an unsolvable problem task"

Domestication is generally assumed to have resulted in enhanced communication abilities between non-primate mammals and humans, although the number of species studied is very limited (e.g. cats, Felis catus; dogs, Canis familiaris; wolves, Canis lupus; goats, Capra hircus; horses, Equus caballus). In species without hands for pointing, gazing at humans when dealing with inaccessible food during an unsolvable task, and in particular gaze alternations between a human and the unsolvable task (considered forms of showing), are often interpreted as attempts at referential intentional communication. We report that kangaroos, marsupial mammals that have never been domesticated, actively gazed at an experimenter during an unsolvable problem task (10/11 kangaroos tested), thus challenging the notion that this behaviour results from domestication. Nine of the 10 kangaroos additionally showed gaze alternations between the unsolvable task and experimenter. We propose that the potential occurrence of these behaviours displayed towards humans has been underestimated, owing to a narrow focus on domestic animals, as well as a more general eutherian research bias.