Brush your teeth and get cleaned up for the week ahead! These animals answered the call of good dental hygiene. Here: Hamster holds toothbrush. (Photo by Neo Vision/Getty Images/Amana Images RM)
A tourist carries her luggage in a flooded St. Mark's Square, in Venice, Wednesday, November 13, 2019. The high-water mark hit 187 centimeters (74 inches) late Tuesday, Nov. 12, 2019, meaning more than 85% of the city was flooded. The highest level ever recorded was 194 centimeters (76 inches) during infamous flooding in 1966. (Photo by Luca Bruno/AP Photo)
Joseph Fons holding a Pride Flag, runs in front of the U.S. Supreme Court building after the court ruled that a federal law banning workplace discrimination also covers sexual orientation, in Washington, D.C., U.S., June 15, 2020. (Photo by Tom Brenner/Reuters)
Israelis take cover as a siren sounds a warning of incoming rockets fired from the Gaza Strip, in Ashkelon, southern Israel, Sunday, May 16, 2021. (Photo by Heidi Levine/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.
With the help of some fake teeth and multiple exposures, New York AP photographer Eddie Adams' daughter Susan is transformed into a little ghoul on Halloween night, October 31, 1966. (Photo by Eddie Adams/AP Photo)