by Janet Spencer
Tape recorders were invented in the 1940s, allowing researchers to record the calls of animals and take them back to the lab for study. This helped them understand the meaning of the calls, and allowed them to play the calls back to the animals in the wild to see the response. The invention of sonar technologies during World War II allowed scientists to discover that bats, dolphins, and whales communicate using methods beyond our capacity to hear. Our understanding of how things communicate has exploded. Come along with Tidbits as we learn about how creatures communicate!
• A small species of tree frog in Borneo came up with a unique way of having its tiny voice broadcast over the noisy jungle. It seeks out small hollows in trees that are filled with water. Submerging itself, it adjusts the sound frequency of its call to fit the size of the hole. Soon it hits the frequency that makes the tree resonate, broadcasting the call like a speaker.
• A vine in the Central American rain forest developed flowers shaped like tiny satellite dishes. The concave petals bounce sound waves outward. This vine depends on bats to fertilize its flowers, and the shape of the flower helps the bats find the flowers amid the noise of the forest. The blossoms only open at nightfall when the bats are out.
• Sound travels best at night, which is why most birds do the majority of their calling at dawn and at dusk, just on the edges of night.
• One scientist carefully analyzed the cacophony of animal sounds that filled the jungle at night. He found that it was not a jumble of random calls; instead, it was a carefully ordered layer-cake of sounds, with each species calling on its own specific frequency. Bats, bugs, crickets, frogs, and mosquitoes each claimed, and communicated on, a single frequency that they did not vary from, and which did not overlap with the frequencies being used by other creatures in the neighborhood.
• This leads to a neighborhood-wide “sound signature” that each individual area carries. Each regional mini-habitat as small as 30 feet wide reveals a different but entirely identifiable symphony. Animals that stray from their home turf are able to make their way home by identifying this signature symphony. On the other hand, animals that have been displaced by logging, development, or natural disasters are unable to find and fit into a new territory with an entirely foreign sound.
• Howler monkeys, native to central American rain forests, open each morning by screeching, a call that can be heard for a mile or more. Each monkey in the tribe screeches, which lets neighbors know how many monkeys there are in the group, ready to defend their territory.
IT’S A FACT
• Colonies of bacteria communicate by releasing chemicals that alert other individual bacteria that they are there: “I’m here!” “I’m here too!” and when they reach a critical mass, they know they have enough numbers to invade. This is likely the oldest form of communication on earth.
CONVERSATION BY ELEPHANT
• In the 1980s a researcher was studying elephants in a zoo. While standing next to one, she felt a strange rumbling in her chest that she couldn’t explain. On a hunch, she recorded the rumbling and then analyzed the recording using a sound spectrograph. Subsequent study showed that two elephants on opposite sides of the zoo were communicating using ultra-low frequencies that are impossible for humans to hear. Further research showed that less than a third of 1,000 hours of recorded elephant calls were audible to the human ear.
• Researchers can identify over 30 different elephant calls.
• Elephants also communicate by scent. Male elephants give off pheromones from glands under their eyes. The odor of a young elephant’s pheromone is rather pleasant, like honey. But as the elephant ages, the scent changes to that of a skunk, and then to “the smell of a thousand goats.” The older the elephant is, the worse he smells, but the females find the odor attractive and will mate with the oldest and most odiferous elephant.
COMMUNICATING BY ODOR
• Pine beetles live in pine trees. A female attracted by the odor of tree sap burrows into the tree. The tree exudes sap to entrap her, but she carries with her a particular fungus that she deposits in the burrow which plugs up the tree’s pores.Then the female releases a pheromone odor to signal other females to come. The odor is ten times stronger than the scent of the sap. They all burrow into the tree while making clicking noises so everyone knows where everyone else is, avoiding intersecting burrows. Next the male beetles arrive, pairing off with the females, and then emitting an odor to signal other males that “this female is taken.” When all the males are giving off the same “no vacancy” odor, other male beetles avoid the tree.
ODORS OF ANTS
• When ants encounter an invader, they release a chemical odor that alerts other ants to the threat and leads them to attack. Meanwhile, each ant also carries a chemical odor that identifies them as a member of the colony. If an intruder is marked with the “I belong here” chemical before entering the anthill, it is left undisturbed.
• All primates use hand gestures to supplement their limited vocal sounds. Many gestures are identical to those used by humans, including palms up meaning “give me some” to pointing. Different groups develop different “dialects” of gestures, so that a chimp from one region may not understand a chimp from another area. This tendency to use gestures convinced researchers to try to teach primates sign language, an experiment that began in the 1920s and continues today.
• Researchers at a zoo in Georgia were trying to teach an adult female bonobo (similar to a chimp) to communicate using pictograms. Each card depicted a different thing. For two years researchers worked with her daily hoping she could learn to construct sentences. During the lessons, the bonobo’s young son named Kanzi would constantly be interrupting as he goofed off. The lessons failed, and the mother bonobo was sent to a different zoo to be mated, while her son Kanzi, now two and a half years old, remained behind.
• To the researcher’s surprise, the youngster almost immediately demonstrated that he was perfectly able to communicate using the pictograms, constructing over 650 sentences and proving that he even understood proper syntax and grammar.
• Now 42 years old, he lives at a facility in Iowa, and knows around 3,000 words. He has even mastered the video game Pac-Man.