Owl, a master of nocturnal hunting.
A pair of majestic eyes, sparkling in the night.
270º barrier-free rotating neck, standing on the tree as long as you twist your head to scan the whole field, leaving no dead corner.
The free-turning neck not only helps the eyes to expand their field of vision, but also helps the ears to collect sound in all directions and determine the source of sound. The owl hunted at night, whose ears are more useful than the eyes, can hear and distinguish the position with only one pair of ears, and catch the mouse hiding behind the obstacle.
In your head is a shaped geomorphological map of your surroundings, which is stored on the visual cortex, and the location of the objects on the map corresponds to the equivalent position on the retina, that is, your map is recorded in the head through the eyes. The owl has a different map than you, and the location of the objects on the map is not from the line of sight, but from the sound, and it can draw the map through the ear.
Before parsing ear hearing positions, let's take a look at the neck that helps the ear collect sound. The owl's strong cervical vertebrae, which twisted left and right, crushed the fragile necks of other animals, including humans.
With its head resting directly on its shoulders, an owl that looks like it has 14 cervical spines, while an owl with a graceful neck curve has only 7 cervical spines.
Above is the skeleton of the spotted owl (African spotted owl), plucking the feathers to see the truth, the owl has a long neck. The multi-segment cervical spine facilitates the owl to rotate its head in a large number of directions, and it not only surpasses us in the number of cervical vertebrae, but also the arterial blood vessels in the cervical vertebrae are much stronger than ours.
Our carotid arteries are very fragile, and a little external force, such as a collision on the brakes, or a wrong massage, can hurt the carotid arteries and tear the inner layer of the blood vessels. In contrast, the owl twists its head all day long, swoops and stops, and no matter how violent the movement will not damage the blood vessels in the cervical spine, and no matter what angle the owl's head is crooked, there will be no shortage of blood supply to the brain, dizziness and fainting. Why is its carotid vertebral artery so much stronger than ours? Two things are different, one is that it has a cache blood bank, and the other is that it has room for activity.
The team at Johns Hopkins University in the United States injected a developer into the owl's artery to simulate blood flow. The team was shocked to find that as the owl twisted its head, the blood vessels at the base of its chin became thicker and thicker, storing more blood. This phenomenon is the complete opposite of ours, when you twist your head, the carotid vertebral artery blood vessels will only get thinner and thinner, and will never become thicker when the head is out of place.
No matter how much the owl turns its head, the cause of cerebral ischemia has been found, and it has a cache bank on its chin that stores the blood that the brain needs. When extreme twisting of the head causes temporary ischemia of the carotid vertebral artery, the cache blood bank can supply blood to the brain in time.
The same is the arterial blood vessel, your blood vessel is close to the lumen of the cervical vertebrae, and the blood vessels have limited space to move in the lumen. The owl's cervical spinal canal lumen is 10 times the diameter of the blood vessels, and the abundant space provides a cushioning cushion for the blood vessels, as well as sufficient places to move. When the owl turns its head at a large angle, the arterial vessels are not compressed by bone friction within the wide lumen.
The flexible cervical spine, free-moving carotid arteries, and a stockpile of blood allow the owl to twist its head unrestrictedly in the 270º range.
The owls' ears are hidden under the feathers and, unlike other animals, have external ears that collect sounds. The owl without external ears relies on a flexible rotating neck to help the ears collect sounds from all directions and catch prey.
To explain: The owl in the picture above has feathers on its head, not ears. [Headlines - France is Bacon - Please do not reprint other platforms without authorization]
We who move in bright light, have sunlight during the day and light at night, and have long been accustomed to relying on our eyes to receive information, ignoring the advantages of the ears.
In fact, the auditory sense covers a wider range than vision. When the light is blocked by a wall, we can't see the movement behind the wall, but we can still hear the purring of the cat behind the wall. Sound waves can both travel through solid walls and around walls into our ears, whereas light can't.
Owls can not only catch rats in the dark nights without a little light, but also catch mice hiding under the snow, all by ear.
You may suspect that an owl can catch prey through its sense of smell or temperature perception, and perhaps its eyes can still see infrared rays, and it is uncertain that the owl is located by its ears. Then look at a classic experiment that is enough to reassure you.
In the dark room, tie a piece of paper to the rat's tail. Rats dragged paper around, and the paper rustled against the floor. The owl pounced exactly on the moving paper, not the mouse. In the dark room, when the owl turns its head from side to side, not to see the mouse, but to listen to the mouse, it uses its ears to find the mouse.
Owls that rely on sound to be accurately located have ears that are different from ours.
Pictured above is the skull of the most common owl, the aegolius funereus. The well-looking owl has a distinctly asymmetrical structure in the skull hidden under the feathers, two ears, one high and one low, with different opening shapes. The right ear opening is up and the left ear opening is facing down. When an owl swoops down from a high place to prey on the ground, the sound coming from directly in front of it will be louder in the right ear than in the left ear. When the owl stays in the tree, the sound coming from directly below will be louder in the left ear than in the right ear.
If the sound is not coming from the front or bottom, but from the side, when it reaches the left and right ears, there is a time difference in addition to the intensity. The speed of sound propagation in the air is 343 m/s, if the distance between the ears is 10 cm, the proximal ear close to the sound hears the sound first, and after 300 microseconds (μs), the far ear hears the sound. The distance of the ears is determined by the size of the head, and the hearing time difference of animals with small heads is shorter.
Our nervous system transmits signals with a time-lapse response time, which is generally considered to be 1 millisecond (ms, 1 second = 1000 milliseconds, 1 millisecond = 1000 microseconds). 300 microseconds is so short that our neural mechanisms can't tell the difference in time. However, many animals, including owls, can distinguish this short-lived microsecond difference in sound.
The picture above is an owl listening to the sound hunting indication, the left picture is the poor auditory intensity, and the right picture is the hearing time difference. When it hears a sound, the left and right ears hear different sounds, the difference being different intensity differences and time differences from the same sound source. It is the two that are different, allowing it to accurately locate the target.
According to the time difference and intensity difference of the sound, the owl calculates the position of the sound source in two directions, one is horizontal and the other is vertical, and these two steps of calculation are carried out in different brain circuits. The owl uses the time difference to determine the horizontal position of the sound, and the intensity difference to determine the vertical position. If it receives more sound in its right ear than it receives in its left ear, it judges that the sound is coming from above.
Horizontally, the owl determines its position with the same accuracy as you, but vertically it is 3 times more accurate than you.
The image above is the result of an owl's hearing experiment, and the coordinates in the figure are azimuth coordinates (horizon longitude). The left figure is the hearing position under different time differences, and the right picture is the hearing position behind the left and right ears. The midpoint blue dot is the actual sound source location, and the red dot is the sound source position determined by the owl when blocking the left ear. The green triangle is the location of the sound source that the owl determines when the right ear is blocked.
For sound from a single sound source, the intensity difference between high-frequency sounds is greater than that of low-frequency sounds, because the wavelength of high-frequency sounds is short, and when bypassing the head, it can reduce sound bending and strengthen reflections. But the time difference between low-frequency sounds is greater than that of high-frequency sounds.
Owls can hear sounds at about the same frequencies as you do, a little narrower than the range of sounds you can hear. But in the frequency range of 1000 to 9000 hertz (hz), the owl's listening sensitivity is 10 times that of yours. It can distinguish between different combinations of frequencies in a complex set of sounds.
The image above is a schematic diagram of the owl listening positioning map, the sound source is projected to the horizontal direction, there is a two-dimensional plan; the sound source is projected to a vertical position, another floor plan. Maps in both directions are combined to form a 3D spatial map.
The spatial map drawn by the sound is stored in the owl brain, located in a place called the extrakumulus nucleus of the midbrain, where different sound positions correspond to different neurons, and the sound from the front activates the neurons at the anterior edge of the hypothalamus, and the lateral voice activates the relatively posterior neurons.
The owl has excellent hearing to draw maps, and it has no less than night vision. The information received by the vision enhances and calibrates its listening map.
How strong is an owl with good ears and big eyes? Look at the numbers: 1 barn owl, more than 1,000 mice caught in 1 year. In the faint moonlight, barn owls have a 90% success rate in hunting mice.
Excellent hearing and night vision, the two combined forces, make the owl an excellent hunting master at night.
#这很科学 #
Resources:
1： “adaptations of the owl's cervical & cephalic arteries in relation to extreme neck rotation”，by fabian de kok-mercado etc. feb.2013，science
2：“the representation of sound localization cues in the barn owl’s inferior colliculus”，by singheiser, m., etc. frontiers in neural circuits
3：“how the owl tracks its prey – ii"，by takahashi, t.t. journal of experimental biology
4：“auditory spatial acuity approximates the resolving power of space‐specific neurons“，by bala, a.d.s., etc. plos one 2
5：“visual modulation of auditory responses in the owl inferior colliculus”，by bergan, j.f. etc. journal of neurophysiology
6：“variability reduction in interaural time difference tuning in the barn owl”，by fischer, b.j., etc. journal of neurophysiology
7：“instructed learning in the auditory localization pathway of the barn owl”， by knudsen, e.i., nature
P.S. Today we update the secrets of nature series, which is the 9th: Bird Hearing.