Sunday, November 24, 2013

Good Vibrations: 7 Animals That Use Vibrations to Communicate

Photo of a male jumping spider.

Although we can’t always perceive them, vibrations provide a critical way of communicating for many animal species.
Scientists think vibrational communication is an ancient sensory mode—one that is still widely used throughout the animal kingdom. Animals from tiny insects to jumbo-size elephants talk to each other using vibrations for many different purposes, from mating and hunting to solving territorial disputes and warning predators away.
Read on to discover some of the animals that use good vibes to communicate.
1. Caribbean White-Lipped Frog
Like many frogs, male Caribbean white-lipped frogs sing to attract mates. But their songs contain more than just pleasing sounds.
When they call, the frogs sit with their rear ends buried in the mud and their head and front legs just above the ground. With each chirp they make, their vocal sacs expand and contract, hitting the ground and producing an accompanying vibration.
The thumps can be felt 10 to 20 feet (3 to 6 meters) away. Since singing males space themselves apart by 3 to 7 feet (1 to 2 meters), each can feel the calls of its nearest neighbors. Scientists think males might use this vibrational information to maintain the distance between them or time their calls so they don’t overlap. (See “‘Deaf’ Frog Hears By Using Its Mouth As An Echo Chamber.”)
2. Jumping Spiders
Male jumping spiders go to great lengths to attract females, putting on colorful and elaborate displays that also include a vibrational component.
Male spiders generate their vibes by rubbing parts of their bodies together, drumming body parts against the ground, and vibrating special organs. These vibrations not only make the female more likely to mate, they also decrease the chances that she will eat her suitor.
There are some jumping spiders that take advantage of other spiders’ vibrational sensitivities to prey on them. These jumping spiders invade a potential meal’s web and mimic the vibrations of an insect struggling to escape. When the spider approaches to investigate, the sneaky trickster makes a meal of it. Other spider species imitate the vibrations of a courting male to attract and then prey on interested females. (Watch video of jumping spiders attacking insects.)
3. Elephants
The low-frequency calls of elephants actually travel farther through the ground than they do through the air—perfect for communicating over long distances. (See “Elephants ‘Hear’ Warnings With Their Feet, Study Confirms.”)
Elephants detect these seismic waves with the skin of their feet and trunk. Researchers have observed elephants in the wild leaning forward and putting more weight on their front legs, presumably to increase ground contact and the sensitivity of their feet.
By using vibrations, highly social elephants can tell each other about danger from miles away. (See “Elephants Communicate in Sophisticated Sign Language, Researchers Say.”)
4. Mole Rats
Mole rats are a group of rodents that live in underground burrows. Under the ground, there is not much light for visual signals, and sound doesn’t travel very far. So several species of mole rats have developed other ways to communicate—like head-banging.
The Middle East blind mole rat knocks its head against the walls of its tunnels to signal to its neighbors. Demon mole rats also head-bang to talk to each other, and the pattern of their banging might even be specific enough to communicate an individual’s identity to its neighbors. 
5. Termites
African termites build giant mounds in which they live and grow fungus for food. If a mound is threatened by a predator such as an aardvark, chains of drumming termite soldiers head-bang an alarm.
To alert the entire colony of an impending attack, termites will bang their heads on the ground about 11 times a second. One termite’s head-drumming travels only about 15 inches (38 centimeters), but any termite close enough to hear the alarm responds by drumming its head too. In this way, the alarm spreads like a chain reaction through the colony. (Related: “Africa’s Mysterious ‘Fairy Circles’ Explained.”)
6. Kangaroo Rats
Like a desert version of Disney’s Thumper, banner-tailed kangaroo rats use foot-drumming to communicate in a number of situations, including when they encounter snakes.
The foot-drumming may be a form of parental care, warning vulnerable offspring that a dangerous predator is near. It could also convey to the snake that the kangaroo rat has spotted it and the reptile should probably look for easier prey elsewhere.
7. Treehoppers
Treehoppers are tiny insects that cling to plant stems and often live in family groups. They communicate with each other by vibrating the stem they’re sitting on. Although none of their signals are perceptible to humans without the aid of specialized instruments, treehoppers produce a surprising variety of vibrational signals.
Young treehoppers will signal to the group when they’ve found a new stem to eat, or to send out an alarm if a predator approaches. Adult males also vibrate to attract mates. Interested females respond to these vibrational courtship songs by vibrating back.


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