But can bison really be sad? Do nonhuman animals ever cry from sadness? Tears are useful for our eyes—as they are for many other animals. A lot of mammals, reptiles and birds have tear glands ...

Animals simply don’t cry. Or at least, they don’t shed emotional tears. The only creatures who have evolved to do so, it turns out, are humans. We snivel at sad movies, well up at weddings and blink ...