A study by researchers from Karl-Franzens-University-Graz in Austria has found that rattlesnakes shake louder to seem like they are close by to warn other animals to stay away.
How researchers conducted the study
The researchers came to this conclusion when they visited an animal facility. They noted that the rattlesnake was louder when they were closer but lower when they walked away.
To investigate their suspicions, they used a human-like torso for their experiment. They found that the rattling rate went from 40Hz or lower to a frequency of 60-100Hz in western diamondback rattlesnakes (Crotalus atrox). The snakes would also adjust the rattling speed according to the velocity of approach rather than the animal’s size.
Researchers also placed other volunteers in a virtual-reality grassland and asked them to guess how far a snake was. Their estimations were closer to the actual distance when the vibrations were slower and occurring at a lower frequency. However, when the rattling was closer, they thought the snakes were nearer than they were.
When the snake rattles slowly, the human ear can pick out every vibration individually. However, when it becomes faster, the vibrations fuse into one sound that is alien to human ears. Because of human perception, the sound seems higher even when the amplitude and loudness are the same.
According to Boris Chagnaud, a senior study author, while the rattling has always been viewed as a simple warning to other animals about the snake’s presence, it is even more complex.
He adds that since these snakes use infrared signals and vibration to detect animals, it only makes sense that their rattling would be more complicated. Rattlesnakes don’t just rattle to indicate their presence but have adapted a sonic distance warning. This is similar to the one found in cars while they drive backwards.
Rattlesnake vibrations are a result of evolution
The random process of evolution can explain this response. The rattlesnakes might have had many encounters with larger mammals and tried to adapt to the auditory response of mammals. This adaptation enabled those who could use mammalian auditory perception to avoid being stepped on and hence survive better.
