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.
Tribes in the frogs' native habitats used the frog poison on their arrows. The frogs' vivid colors warn potential predators they aren't safe to eat. As adults, poison dart frogs are carnivores, yet many are omnivores as tadpoles, says National Aquarium Curator Ken Howell on the organization's website. Native to Central and South American rainforests and to some Hawaiian islands, poison dart frogs hunt spiders and small insects such as termites and ants.