Nature presents humanity with countless mysteries, and we tirelessly work to unravel them one by one. The otter, which inhabits rivers, primarily feeds on fish. There are no recorded instances of otters eating anything else during the winter months. But come spring, the otter often starts eating grass, and when berries appear it leaves the water to feast on them. Why does the otter seek out plant foods in spring and summer when it gets by fine on fish in winter? It’s a puzzler.
That mystery has been solved. The otter swallows fish whole—scales and bones included. In winter, its stomach produces enough hydrochloric acid to dissolve the bones completely. As spring and summer arrive, its acid production drops, causing a buildup of undigested fish bones in the stomach.
That’s when it diversifies its menu. Grasses and berries supply the chloride the otter needs to make hydrochloric acid. That’s why it devours them so eagerly.
