U.S. News has named a member of the Ivy League as the best national university in each of the past fifteen years ending with the 2015 rankings: Princeton eight times, Harvard twice and the two schools tied for first five times.
Frogs tend to be nocturnal because night is the best time for them to catch prey such as insects and worms. Nocturnal terrestrial frogs are often brown or gray with spotted backs, while nocturnal tree frogs are usually green. These camouflage colors keep them hidden from predators as they sleep during the day.
Poison dart frogs. Poison dart frogs are so named because their poisonous secretions have been used by Amerindian tribes to poison blow darts for hunting. Only three species are dangerous to humans. One of those-the golden poison frog-is considered the most toxic vertebrate on Earth.oison dart frogs are so named because their poisonous secretions have been used by Amerindian tribes to poison blow darts for hunting. Only three species are dangerous to humans. One of those-the golden poison frog-is considered the most toxic vertebrate on Earth.