One of the most beautiful and popular frogs in North America is the American green tree frog.  It is approximately 2.5 inches long and bright yellow-green to olive green in color.  However, like other amphibians, it can change its color.  Typically, the American green tree frog is more yellow when it is calling and a darker green when at rest. Even though the American green tree frog frightens easily and cannot be handled too often, it is a common pet.  It is easy to care for and does not need artificial heating.  Its only requirement is a tall aquarium and foliage to climb on.  Many owners claim these frogs have distinct personalities and are very curious.  These frogs are known to chase and eat faster insects instead of the slow-moving ones.  American green tree frogs can become obese as pets and it is wise to make sure they are given room to move and catch their food. Frogs are known as an "indicator species."  The more frogs in an area, the healthier that area is.  As of 2019, the American green tree frog is a species of least concern, but a decrease in its numbers could mean a problem in its habitat.  The United States Postal Service issued four frog stamps in 2019.  These serve as a reminder of how important frogs are so we can continue to ensure their survival for years to come.