Tag Archives: frequency

Rattlesnakes modulate their tail wagging to make you think they’re closer than they are

The rattling of rattlesnakes isn’t as simple a warning as we assumed. New research explains that this sound is subtly modulated to change the listener’s perception of its source, making it seem the snake is closer than it actually is.

Image via Pixabay.

Rattlesnakes are quite famous for the warning sounds they produce with their tails, the iconic ‘rattling’ that gives them their name. Far from being a simple wagging of the tail, however, new research suggests that this rattling is a fine-tuned intimidation tool. As the snake rattles its tail, it makes an abrupt shift to a high-frequency mode, the team explains. This makes listeners perceive the source of sound as being closer than it actually is.

In effect, while definitely being deadly, rattlesnakes also engage in some strategic deception.

Rattle my bones

“Our data show that the acoustic display of rattlesnakes, which has been interpreted for decades as a simple acoustic warning signal about the presence of the snake, is in fact a far more intricate interspecies communication signal,” says senior author Boris Chagnaud at Karl-Franzens-University Graz. “The sudden switch to the high-frequency mode acts as a smart signal fooling the listener about its actual distance to the sound source. The misinterpretation of distance by the listener thereby creates a distance safety margin.”

Past studies have shown that rattlesnakes’ rattles vary in frequency, but they didn’t give us any insight into why they do, or what this behavior actually achieves in the real world.

The hypothesis behind this paper was born while Chagnaud was visiting an animal facility and noticed that rattlesnakes increased the frequency of their rattling as someone approached the snakes — but decreased when they walked away. From this observation, Chagnaud and his team developed an experiment in which objects appeared to move towards rattlesnakes. One of these objects was a human-like torso, and another was a looming black disk. The illusion of forward-back movement was created by making the objects increase or decrease in size.

The team reports that over the course of this experiment, as potential threats approached the snakes, they would increase the frequency they rattled at to approximately 40 Hz. But, abruptly, they would switch to an even higher frequency range, between 60 and 100 Hz.

Further experimentation revealed that rattlesnakes adapt their rattling frequency to the (perceived) approach velocity of an object, rather than its size.

“In real life, rattlesnakes make use of additional vibrational and infrared signals to detect approaching mammals, so we would expect the rattling responses to be even more robust,” Chagnaud says.

Inside a virtual reality environment, the team then tested how this shift in rattling frequency is perceived by a person or animal close to the snake. A group of 11 participants were asked to engage in a simulated walk inside the virtual environment — a grassland — and told they’ll be walking towards a snake. Its rattling rate increased as the participants closed in, as per the previous findings, and suddenly raised it to 70 Hz at a virtual distance of 4 meters.

The participants were asked to tell the team when the rattling sounded like it came from only 1 meter away. All the participants underestimated the distance that the virtual snake was at after it increased its rattling frequency.

“Snakes do not just rattle to advertise their presence, but they evolved an innovative solution: a sonic distance warning device similar to the one included in cars while driving backwards,” Chagnaud says. “Evolution is a random process, and what we might interpret from today’s perspective as elegant design is in fact the outcome of thousands of trials of snakes encountering large mammals. The snake rattling co-evolved with mammalian auditory perception by trial and error, leaving those snakes that were best able to avoid being stepped on.”

The paper “Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans” has been published in the journal Current Biology.

Looking at the universe naked – an Ontological Awakening

It was Stephen Hawking who said:

We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the universe. That’s what makes us special.

The pictures showcase the universe in its cosmic brilliance. Spanning the entire electromagnetic spectrum, these images have been false- colored to help us perceive the universe that lies beyond our visual cognizance.

Breathtaking isn’t it ?

Courtesy: Chromoscope.

 

 

Blue whales singing lower every year, baffled scientists say

Blue whales are not only the biggest living creatures in the world right now, but the biggest ever to have ‘walked’ the face of the earth; they’re also the loudest for that matter. After recovering from near extinction in the beginning of the 20th century, blue whales are finally getting a part of the respect they deserve.

However, researchers cannot understand what is causing these majestic creatures to ‘sing’ at lower frequencies year after year. No one is fully sure of all the uses of the blue whale songs, but it’s known they are used to communicate and as a mating ritual. However, ever since the 1960s, the frequencies which these giants use are getting lower and lower, without anybody being able to give an explanation.

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Of course, some theories have emerged, the two most likely being that it’s a direct result of the water pollution or a sign that an almost extinct population is recovering. Mark McDonald, president of Whale Acoustics, a company that specializes in recording the songs of blue whales (yeah, really) originally thought the cause could be noise pollution caused by intensified traffic; however, if this would be the case and they would want to make themselves heard louder, they would use higher, and not lower frequencies. This may be a bit weird because generally lower frequency transmissions are used for long distances, but mister McDonald explains:

Across the frequencies of blue whale song, the underwater transmission losses are nearly the same regardless of frequency. It is absorption which is the primary cause of frequency dependent transmission losses, rather than dispersion in this case, and the absorption loss only begins to become significant when ranges reach thousands of kilometers. Theory tells us the whales can produce higher amplitude songs at higher frequencies, based on given lung volume.

whales

Another possible reason could be a change in the mating rituals. Scientists have long known that only male blue whales sing, and larger (which are usually more mature) specimens sing at lower frequencies. The hypothesis is that the younger guys are trying to emulate the older ones in order to attract females (that seems familiar). Either way, there are many we have yet to understand about the way these marine mammals act. The only good thing is that the blue whale populations is nearing a normal limit; let’s set this as an example for other species too, instead of treating them with less care now that they’re not on the brink of extinction anymore.

Mosquitoes make harmonic music before making sweet love

So the male mosquito comes, humming an Elvis song, with a rose in his mouth… maybe I’m taking this a bit too far. You know that pesky mosquito sound ?? Scientists have known for years that that is the sound of love for the little buggers.

But what they didn’t know, and is quite fascinating in a way, is that males and females flap their wings in a certain way, to create a harmonic tune duet just before mating. According to renowned profesor of neurobiology and behavior Ron Hoy, they “interact acoustically with each other when the two are within earshot — a few centimeters of each other”.

“The frequency at which males and females converge is a harmonic or multiple of their wing-beat frequencies, which is approximately 400 hertz [vibrations per second] for the female and 600 hertz for the male,” adds Hoy.

If that’s not romance, I don’t know what is.

The frequency at which they “sing” when they’re mating is very high (1.200 hertz), about an octave higher than the standard A at which instruments are tuned. What’s a bit more interesting (especially if you have a bit of musical knowledge) is that they set their thoracic box to produce a frequency that converges to the frequency that is the female’s third harmonic, that’s three times her natural frequency; and despite whatever you may think, this is actually useful.

“By studying these flight tone signals, we may be able to determine what kind of information males and females consider important when choosing a mate,” said co-first author Lauren Cator, a Cornell graduate student who works with Harrington. “This will allow us to release ‘sexy’ transgenic or sterilized males that will be able to successfully compete with wild populations.”