Because a frog lives on land and in water, he has a number of sensory organs that make him well-suited to both environments. Most of these sensory organs are on the frog’s head, because a frog needs to be vigilant -- he is both predator and prey. He can keep his head just above the surface of the water to take in sights, sounds, smells, tastes and other sensations, while his body remains hidden underwater.
A tadpole’s eyes are on the side of his head. As he develops into an adult frog, the eyes move to the top of his head. Most frogs have large eyes, placed to let them see to the sides and behind without moving. A frog also has excellent night vision and depth perception, and he can detect the slightest movement.
A frog does not have outer ears, but he does have an eardrum on each side of his head, called a tympanum. The tympanum transfers sound vibrations to the inner ear. The tympanum also allows the frog to maintain a sense of balance. A frog listens for a variety of calls from other frogs. Males listen for the calls of rival males, and females listen for the calls of potential mates. Frogs also listen for distress calls from other frogs that warn when a threat is present.
Like us, a frog uses his two nostrils to sample odors in the air. He also has a second type of olfactory organ between the nostrils, called the Jacobson’s organ. It is used to detect chemicals in the water. Because all of his olfactory organs are on the top of his head, the frog can sample air and water odors simultaneously by putting his nostrils just above the water’s surface.
A frog will eat just about any living thing he can fit in his mouth, but he also has sensitive taste buds. He will occasionally spit out hastily grabbed prey if the taste is unpleasant. The taste buds are on the surface of his tongue and the inside of his mouth. Completely aquatic frogs in the Pipidae family do not have tongues, but they have taste discs in their mouth tissue to receive taste sensations.
Through his skin, a frog can learn a lot about himself and his environment. He can detect temperature, pressure, touch and pain. An aquatic frog has one additional feature, making him uniquely adapted for life underwater -- the lateral line. The lateral line receptors are present not only on the head and around the eyes, but on the body and neck as well. They detect vibrations through the water, giving the frog an idea of the shape and direction of a prey item in the water.
- Herpetology: An Introductory Biology of Amphibians and Reptiles, George R. Zug et al.
- Frogs: A Chorus of Colors; John L. Behler et al.
- Biology Teaching and Learning Resources: Frogs - an Introduction
- Britannica Online Encyclopedia – Jacobson’s organ (zoology)
- Physics News Update - Good Vibrations Help a Frog Locate Tasty Prey
- Sensory Evolution on the Threshold: Adaptations in Secondarily Aquatic Vertebrates; J. G. M. Thewissen, Sirpa Nummela
- Digital Vision/Digital Vision/Getty Images