In animals, yawning can serve as a warning signal. For example, Charles Darwin, in his book The Expression of the Emotions in Man and Animals, mentioned that baboons yawn to threaten their enemies, possibly by displaying large canine teeth. Similarly, Siamese fighting fish yawn only when they see a conspecific (same species) or their own mirror-image, and their yawn often accompanies aggressive attack. Guinea pigs also yawn in a display of dominance or anger, displaying their impressive incisor teeth. This is often accompanied by teeth chattering, purring and scent marking.
Audience take photos of a model presenting a creation by Greek designer Dimitrios Ordoulidis during the 10th Athens Exclusive Fashion Week in Athens, Greece, October 22, 2016. (Photo by Alkis Konstantinidis/Reuters)
Guests attend the Hollywood Forever 2023 Dia De Los Muertos Celebration at Hollywood Forever on October 28, 2023 in Hollywood, California. (Photo by Emma McIntyre/Getty Images)
Overall winner: The Art of Flight by Alwin Hardenbol (University of Eastern Finland). A panning shot of a Dalmatian pelican in flight. The picture was taken on Lake Kerkini in Greece. (Photo by Alwin Hardenbol/2020 British Ecological Society Photography Competition)
Relatives of inmates of the «Santiago 1» jail react outside the prison after a large number of prisoners attempted to escape amid panic over the spread of the COVID-19 coronavirus in Santiago, Chile, on March 19, 2020. (Photo by Javier Torres/AFP Photo)