Alligators Detect Water Movement
with Special Sensory Receptors

August 8, 2002

We humans have some great ways to find out about the world around us. For example, we use our eyes to gather information about movement, shape and color. Our ears allow us to hear sounds with frequencies between 20 Hz and 20,000 Hz. We use our noses and taste buds to learn about food, and special receptors in our skin tell us about texture, pressure and temperature.

Although our senses are well suited to our environment, many animals are equipped with sensory systems that we lack. For example, rattlesnakes have a sensitive organ between their eyes and nostrils to detect heat. Penguins can see into the ultraviolet range. Alligators have special sensory receptors to detect ripples in the water, according to new work done by Daphne Soares, a graduate student in the Department of Biology at the University of Maryland.

Soares knew that the jaws of alligators and other crocodilians are lined with small domes. She also knew that half submerged alligators lunge at or turn toward drops of water even if the animals are in complete darkness and can't hear anything. To test the function of the domes, Soares covered the domes with plastic. With covered domes, the alligators stopped reacting to drops of water. Soares also recorded the activity from nerve cells that innervated the domes and found that they responded to pressure.

Soares believes that these special sensory receptors, which she calls dome pressure receptors (DPRs), are used by crocodilians to hunt, especially at night. Small disturbances on the water, such as that caused by a bird or frog, may trigger the DPRs and help the alligator catch its next meal.

References and further information:

  1. Soares, D., An ancient sensory organ in crocodilians. Nature, 417:241-242, 2002.
  2. Crocodilians
  3. Movies of alligators from Soares' experiments!

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