A seal infront of a passing cruise ship on the shore between Sandhaven village and Fraserburgh in Scotland in August 2023. (Photo by Mark Grant/Caters News Agency)
A boy takes his basset hound for a walk with a difference in Noosa, Australia on Saturday, March 9, 2024, during the annual Surf Dog Championships. (Photo by Roberta Holden/Solent News)
A tourist visits an ocean park during the International Day for Biological Diversity on May 22, 2024 in Handan, Hebei Province of China. May 22 marks the 24th International Day for Biological Diversity. (Photo by Hao Qunying/VCG via Getty Images)
In this Wednesday, May 23, 2012 photograph, a young deer and a cat share a moment in Feench village near Jodhpur, Rajasthan state, India. (Photo by AP Photo)
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.