An empty cell block is pictured within Joint Task Force Guantanamo's Camp VI at the U.S. Naval Base in Guantanamo Bay, Cuba March 22, 2016. (Photo by Lucas Jackson/Reuters)
An Israeli Air Force F-35 fighter jet flies during an aerial demonstration at a graduation ceremony for Israeli airforce pilots at the Hatzerim air base in southern Israel December 29, 2016. (Photo by Amir Cohen/Reuters)
LA-based model Tori Brixx at the BET Awards 2023 held at Microsoft Theater on June 25, 2023 in Los Angeles, California. (Photo by Broadimage/Rex Features/Shutterstock)
People look at a collection of vintage cars during the Expo Transporte event at the Francisco de Miranda Air Base in Caracas on December 7, 2025. (Photo by Juan Barreto/AFP Photo)
BASE jumper Luke Denniss of Australia gestures as he dives in the air from the Kuala Lumpur Tower during the KL Tower International Jump in Kuala Lumpur, Malaysia, Saturday, September 27, 2014. BASE stands for the places such jumpers usually jump from: buildings, antennas, spans (bridges) and earth (cliffs). (Photo by Lai Seng Sin/AP Photo)
Base jumper Denis Odintsov from Russian leaps from the 300-meters Open Deck of the Malaysia's landmark Kuala Lumpur Tower during the International Tower Jump in Kuala Lumpur on September 27, 2013. Some 103 professional base jumpers from 20 countries are taking part in the annual event. (Photo by Mohd Rasfan/AFP Photo)
Giant pandas are playing and foraging inside the Shenshuping base of China Conservation and Research Center for the Giant Panda in Wolong National Nature Reserve on November 3, 2021 in Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province of China. (Photo by An Yuan/China News Service via Getty Images)
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.