Why can animals drink swampy water that wouldn't be safe for humans?

Jerry Pruzan | North Bethesda, Maryland

 Jerry Pruzan | North Bethesda, Maryland

HUMANS TEND TO LIVE in sterile environments that limit our exposure to contamination, so our immune systems aren't used to protecting us against certain pathogens that may be in swampy water. Animals may be exposed to contaminated water on a regular basis and build up resistance that protects them against those pathogens. Some wild animals also have a strong sense of smell that helps them identify safe water to drink, and many animals have strong digestive systems that are better suited than ours to consume swampy water safely. It's also true that not all things that may make a human sic k would affect all animals the same way. For example, salmonella bacteria are a natural part of a snake's or a turtle's body system, but the same bacteria could make humans very ill. Of course, some animals do get sick from the same causes we do. We call those animals "sentinels," since we can study what is making them sick and find out what might happen to humans if we were exposed.

  Katrina Lohan and Calli Wise, 

parasite ecologist and research technician,

Smithsonian Environmental Research Center w York