Visitors pose for a picture next to a mallard duck on the cobblestones of St Peter's Square with St Peter's Basilica in the background at The Vatican, on May 5, 2025. (Photo by Alberto Pizzoli/AFP Photo)
One of the Siberian tiger twins, born on April 13, 2025, is presented to the press at the Budapest zoo and botanic garden, on June 12, 2025 during their first veterinary examination. (Photo by Attila Kisbenedek/AFP Photo)
Mott Sreymom, 34, a rat handler with the humanitarian demining organization APOPO, carries an African giant pouched rat back from a landmine field in Siem Reap, Cambodia, Tuesday, June 10, 2025. (Photo by Anton L. Delgado/AP Photo)
Yanna Xian, 24, and her boyfriend Mitch Brown, 27, were swimming while on a boat tour off Honolulu, Hawaii last year, when a curious two-week-old humpback approached them. (Photo by South West News Service)
A small flock of birds seems to be giving an escort to an airliner on final approach to Reagan Washington National Airport in Arlington, Virginia on January 12, 2022. The scene took place over Gravelly Point which is an area within the National Park Service's George Washington Memorial Parkway. (Photo by Michael S. Williamson/The Washington Post)
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.
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)