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Visible black integumentary sensory organs – ISOs – allow American alligators to detect underwater quarry, pressure changes and possibly even water salinity levels.

American alligators can have more than one ISO on a scale. And while ISOs are distributed all over an gator’s body, they are generally found around the reptile’s head region.  “Integumentary sensory organs look like little black dots,” says Matt Evans, biologist at the Smithsonian National Zoological Park. “They are an external organ present in the layer of the skin… On alligators, they are often concentrated around the jaw areas. ISOs can potentially detect the proximity of prey in murky waters and are sensitive to changes in salinity… we are just now beginning to understand the full extent of these unique organs.”

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Skilled swimmers, this species thrive in freshwater lakes, rivers, swamplands and marshes of the southeastern United States. Remarkably, many experts say that American alligators have been around for over 150 million years.

Learn more about American alligators and read this Inside WILD blog post on Alligator Wrangling.

Check out Swamp Men on Nat Geo WILD tonight starting at 7P et to see wild alligator wranglers at work in the Everglades.

Photo Credits: Jodi Kendall