It has been revealed for the first time that reptiles can change the way they communicate according to environmental noise, such as the complex voice communication methods of birds and mammals.
The Tokai Gecko lizard, which is mainly active in the nighttime in Southeast Asia, communicates with the loudspeakers at different volumes depending on when there is environmental noise and when the surroundings are quiet, the researchers of the Max Planck Institute for Ornithology in Zeben, Germany, said.
The lizards did not control the amplitude of the sound, but they produced a louder syllable in noisy conditions.
This discovery has revealed that the communications system of non-bird reptiles is much more complex than previously thought. Reptiles, like mammals and birds, are capable of sophisticated signaling.
The feature of sophisticated voice communication methods of algae and mammals is the high degree of plasticity, in which the signal is individually adjusted as the environment changes.
As one of these mechanisms of vocal plasticity is the Lombard effect, the call amplitude increases equally as the level of ambient noise increases. The Lombard effect involves the duration of the signal, which helps detect the signal of the noise.
Some species of non-algae reptiles have voice communications such as the nocturnal Tokai Gecko lizard in Southeast Asia.
These lizards are especially loud gecko and cry, so their scientific name is also gecko gecko (Gekko gecko).
This crab-nosed sound plays an important role in the communication of the Tokai-gecko lizard as a sound to seduce a female and to woo other males. In front of this sound, the low-amplitude chuckle makes a sound.
For this research, Henck Broome and Suzanne Zollinger of the Max Flink Ornithological Institute exposed the Tokaekiko lizard to a noise of about 65 decibels (A), which corresponds to traffic noise on crowded streets. They expected the Lombard effect to emerge from this reptile.
In comparison with the control group that was actually in a quiet environment, the duration of Tokai Gecko crab sounds in a noisy environment increased by 7% and the duration of nose sounds increased by 37%. Tokai Gecko lizards and other reptiles can adjust their sounds according to the surrounding conditions.
However, the Tokai Gecko lizard did not increase the amplitude of the syllable in relation to the background noise level, so the researchers did not find the Lombard effect.
"Research has shown that the Lombard effect has evolved independently from birds and mammals," said Broome, a research group leader.
However, the Tokai Gecko lizard produced more loud crab-nasal syllables instead of increasing the amplitude of each sound component, and produced fewer loud noises when there was ambient noise.
"The communication method has developed because of the fact that the signal arrives at the intended recipient regardless of each animal group," said Zoellinger, co-author of the study.