Stomach acid helps us by aiding in the digestion of food. Additionally, it helps kill off harmful bacteria in our food, hence why many scavengers have strong stomach acid (Vultures, Hyenas, etc.) to combat the harmful bacteria in the food they eat.

Stomach acid is measured in pH, where a smaller pH is stronger acid. For example, the white backed vulture has a stomach pH of 1.2 and a great white shark has a pH of 1.3. Some other animals with strong stomach acid include humans (pH 1.5), bald eagles (pH 1.3), ferrets (pH 1.5), possums (pH 1.5), owls (pH 1.3), and the common buzzard (pH 1.1).

Stomach acid isn’t the only factor in food digestion, digestive enzymes and bacteria in the intestine perform the bulk of breaking the food down to extract its energy. For this reason, even though humans have stronger stomach acid than cows, they still can’t digest cellulose so they cannot eat only grass like cows do. So having the strongest stomach acid doesn’t necessarily mean the animal can digest food the fastest or survive off the most sources of energy.