Slimy saliva contains digestive enzymes that help canines (and humans) break down their food. Saliva also wets the throat for a smooth snack-slide right into the belly. But that all happens inside the body.
Drooling occurs when there's a saliva spill. It's simply biomechanics:
Some dogs, such as bulldogs and mastiffs, have such short snouts they have trouble containing their saliva and the leakage constantly pours out. Bow-wows with folded skin around their mouths, such as St. Bernards, bloodhounds and Bassett hounds, are also big drippers.
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Jeanna served as editor-in-chief of Live Science. Previously, she was an assistant editor at Scholastic's Science World magazine. Jeanna has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland, and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species. She also received an ocean sciences journalism fellowship from Woods Hole Oceanographic Institution.