Bonnie Morgan arrives at the LA Premiere of “Rings” at the Regal LA LIVE Stadium 14 on Thursday, February 2, 2017, in Los Angeles. (Photo by Willy Sanjuan/Invision/AP Photo)
The endangered kea is the world’s only alpine parrot, and one of the most intelligent birds. They show no fear of humans and are thieves and pranksters. The parrot is seen in the Whakaari conservation area, near Glen Orchy in the Otago region of New Zealand, a place where historic huts and mining relics are surrounded by stunning mountains covered in tussock. (Photo by Murdo MacLeod/The Guardian)
A baby baboon appears to ride its mother like a horse at the Chobe River, in The Chobe National Park, Botswana, Southern Africa in January 2023. Young monkeys often ride on their parent's backs, like this Chacma baboon, for protection. (Photo by William Steel/Solent News & Photo Agency)
In this September 27, 2017 file photo, girls walk past a wall riddled with bullet holes from shootings between rival drug traffickers, at the Rocinha slum, in Rio de Janeiro, Brazil. Violence is on the rise in Rio's slums after several years of decline, and the killings of kids have shocked even residents long inured to deaths from gangs and police. (Photo by Silvia Izquierdo/AP Photo)
American actress Anya Taylor-Joy and Australian actor Chris Hemsworth are seen on May 08, 2024 in Los Angeles, California. (Photo by PG/Bauer-Griffin/GC Images)
A shepherd and his flock in the Bitlis province of eastern Turkey in the first decade of April 2024. Shepherds regularly embark on gruelling journeys through the dusty outback, as they take their sheep to the high plateaus needed for grazing and then back to villages for milking. (Photo by Kahraman Kaya/Solent News)
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.