The natural world is full of creatures that differ in their unusual method of movement, appearance, gastronomic preferences, behavior, etc. Of course, there is nothing unusual for them themselves, because all this is the result of hundreds of thousands of years of evolution aimed at the survival of the species in constantly changing environmental conditions. What is necessary for an animal becomes for us the object of research and inspiration in developments used in a variety of industries, from medicine to robotics. So scientists from the Georgia Institute of Technology (USA) decided to conduct a detailed analysis of the elephant's trunk, with the help of which the herbivorous giant is able to drink and collect food. What happens to the trunk when the elephant drinks, what force does it use when it picks up small objects,and where can the obtained data be applied? We will find answers to these questions in the report of scientists. Go.
Basis of research
Although elephants are the largest owners of a trunk, they are far from the only ones. Butterflies, tapeworms, leeches, bedbugs, tapirs, elephant seals, etc. - they all have some form of trunk. In various cases, the trunk serves as an organ of touch, nutrition, and even protection.
For elephants, the trunk, formed from the nose and upper lip, is a kind of "Swiss knife". With its help, they collect water (which is then poured into their mouth), pick up small objects, pluck fruits, breathe while crossing water bodies, use in communication with their relatives, etc.
Image # 1
One African elephant ( Loxodonta africana) consumes more than 200 kg of vegetation daily, spending about 18 hours a day harvesting grass, leaves, fruits and tree bark ( 1a ).
The most surprising thing is that an elephant's trunk can weigh about 100 kg, but an elephant can easily pick up a small and fragile object from the floor without damaging it. The secret of such accuracy lies not only in the flexibility and mobility of the trunk, but also in the air that it sucks in. Scientists have suggested that the nostrils and lungs of the animal play an important role in how the elephant manipulates the trunk. During the absorption of water, certain changes also occur due to muscle contraction, which allows the elephant to receive more water in one go.
The fact that elephants use water and air as additional tools to manipulate objects in the environment was described back in 1871 by Charles Darwin. He noticed that elephants can move objects out of their reach by blowing through their trunk. Elephants can adjust the duration of the blow based on the distance to the object, and even deliberately direct a jet of air at the wall, which will then push the object closer to them.
Scientists note that animals that manipulate objects with a stream of fluid usually live in water, not on land. A striking example is fish from the genus Toxotes (sprayers), capable of shooting a stream of water at insects above the surface of the reservoir.
Splatter on the hunt.
Squids and octopuses also shoot water, but not for hunting, but for movement. Many species of fish use what is called "suction feeding", where they suck food into their mouth.
Given the uniqueness of this behavior among terrestrial creatures, elephants and their trunks require study, scientists say. Therefore, several tests were carried out, during which scientists recorded any changes in the morphology of the elephant's trunk during feeding, water intake and manipulation of small fragile objects.
Research results
During the tests (14 runs), the experimental elephant was fed rutabagas cut into cubes of different sizes. The trunk grip varied depending on the size and number of dice ( 1b ). When the elephant was given 10 small cubes (less than 40 mm), he used the tenacious end of the trunk without suction. If there were more than 10 small cubes, then the elephant preferred absorption ( 1c ). It's funny that scientists characterized the sound that accompanied this process as the sound of a working vacuum cleaner.
Methods for collecting small (16 mm) and large (32 mm) rutabaga cubes. In the first case, there is suction (note the sound). In the second, it is not there, since the cubes are too large.
Curiously, during the grain tests, suction was not used, instead the elephant tried to grab as many grains as possible in a handful. Most likely there was no suction to prevent the grains from getting stuck in the trunk.
Then the elephant's meal continued with chips (tortilla) in order to evaluate its interaction with large flat objects. The thickness of the chip is not more than 500 microns, therefore it is difficult to lift it from a flat surface (a force platform was used). To break the chip, you need to apply a force of 11 ± 2 N (Newton), which is about 1% of the weight of the elephant's trunk.
After the first contact, the process of raising the chip took 3.0 ± 0.2 seconds. The process itself can be divided into three stages ( 1d and 1e ): approaching the object, searching for the object, lifting the object.
Attraction of chips by air suction (video slowed down 5 times).
At first, the elephant did not touch the chip directly, but touched the outer edge of the force platform, while applying a force of 4 ± 1 N. During the search phase, he approached the chip, applying a force of 5 N, i.e. 50% of the strength required to break the chip.
During the ascent phase, two different behaviors were observed. In the first case, the elephant applied suction at a fixed distance from the chip ( 1d ). In the second, he applied suction, pressing the trunk directly to the chip ( 1e ). It is also curious that, in any case, the elephant almost always lifted the chip without damaging it.
Visual observation of elephants, while fun, provides too little data. Therefore, scientists additionally measured the created suction pressure during tests with water. In order to better visualize the flow sucked in by the trunk, chia seeds were added to the water. The flow profile appears to be parabolic, as evidenced by the greater distance traveled by the chia seeds in the center of the nostrils ( 2a ).
Image # 2
Graph 2c shows the course of the liquid flow in the trunk over time, measured as the liquid in the reservoir decreases. During three test runs, the elephant sucked in water for 1.5 ± 0.1 s, which corresponds to the volumetric flow rate Q w= 3.7 ± 0.3 l / s. And here scientists again make a strange comparison (for Americans, this is quite normal practice): such a volumetric flow is equivalent to 20 toilet flushes (I do not know how such a comparison can help to assess or visualize the strength of the flow, but okay).
Water suction experiment.
The total volume of liquid in the trunk was 5.5 ± 0.41 liters. After suction of 3 liters, there was a pause of about half a second, at which time the flow rate was 1 ± 1.2 l / s. The flow then increased again to 4.5 ± 2.1 l / s for the last half second of the suction cycle. A similar dynamics was observed during all observations. Scientists suggest that short breaks during absorption are necessary to prevent water from entering the posterior sphincter of the trunk.
For further analysis, it was necessary to establish the internal volume of the trunk (approximately 1.9 m long). For this, data from measurements of the cross-section of the trunk were used. The trunk cavity has a radius of 1 cm at the distal end and 3 cm at the proximal end. The estimated volume of the trunk in this case will be 5.2 liters, which is almost equal to the volume of water drawn in (5.5 liters). How can an elephant draw in more water than its own trunk? Previous studies have shown the presence of a muscle structure extending from the nostrils that allows the trunk to expand.
Further, the scientists conducted ultrasound examinations ( 3a) to find out the limits of the expansion of this structure. Ultrasonographic measurements of the trunk walls were carried out under three conditions: natural respiration, water intake, and bran water intake.
№3 image
in image 3c and 3d it is seen that the radial muscles contracted when elephant drew water from the bran.
Ultrasound examination of the nasal wall of an elephant during bran absorption. The red arrow marks the border between the fluid and the nasal wall.
The initial radius of the trunk and nostril is 7.5 and 1.5 cm, respectively. Consequently, the thickness of the investigated trunk wall is 6 cm.When water was sucked in, the wall thickness decreased to 5.7 cm, and when water with bran was absorbed, to 5.6 cm.It
was found that the radius of the nostril during the absorption of air, water and water with bran was: 1.5 ± 0.2 cm, 1.8 ± 0.2 cm, and 1.9 ± 0.2 cm, respectively ( 3e ). Thus, the values of the radius during the absorption of water and water with bran increased by 18% and 28%, respectively.
If we assume that the radius increases along the entire length of the trunk, then the internal volume of the trunk increases by 40% for water and 64% for bran water.
However, every system has its limit. Scientists have created a mathematical model to calculate the effective distance for suction feeding ( 2d ). The model allowed us to establish the maximum pressure used in experiments with water, and the maximum distance from the chip, at which the elephant can lift it using suction.
In experiments with water, the average water velocity (u w ) in the trunk is the flow rate divided by the cross-sectional area of the nostrils: Q w / (2πa 2) ∼ 2.7 m / s, where a = 2.1 cm is the radius of the nostril. The maximum pressure was observed at the end of the suction cycle, when the water reaches its maximum velocity and height in the trunk. By calculating the Reynolds number * of the flow inside the nostril, you can find out if the fluid is experiencing turbulence.
Reynolds number * - the ratio of inertial forces to viscous friction forces in viscous liquids and gases.The Reynolds number for transporting water through the pipe is Rew = 8.1 x 10 4 , and the Reynolds number for air is 4.2 x 10 6 . Given that these Reynolds numbers are higher than 4000, Bernoulli's law * can be used for approximation . As a result, the applied pressure was found to be -20 kPa.
Bernoulli's law * - if the fluid pressure increases along the streamline, then the flow rate decreases, and vice versa.If the same pressure is applied during the suction of the chip, then the air speed is 150 m / s. Calculations also show that the distance at which an elephant can effectively attract objects is linearly dependent on the size of the nostril. Therefore, an object with a smaller mass or a larger area can be efficiently absorbed and at a greater distance than during experiments with chips.
In the experiments, the surface area of the chip was 113 cm 2 , and the mass was 10 g. Taking into account the acceleration of gravity (in the calculations it was 9.81 m / s 2 ) and the calculated pressure (-20 kPa), the scientists found that the maximum effective suction height is 4.6 cm.
The most important aspect affecting the effectiveness of suction is the pressure in the elephant's lungs. Elephants can create high pressure in their lungs due to their specialized respiratory system. An extensible network of collagen fibers fills the pleural space, freely connecting the lungs to the chest wall, while not restricting lung movement in relation to the chest wall ( Why does an elephant have no pleural cavity ? , John B. West, 2002).
It is this anatomical feature that allows air currents to be generated at such a high speed. In addition, the endothoracic fascia * in elephants is eight times thicker than in humans, rabbits, rats and mice, which can create additional pressure in their lungs.
* — , . .
Image # 4
In conclusion, the scientists, based on the data obtained, decided to determine whether other animals are capable of attracting objects by suction, like elephants. First, the ratio of body weight to the radius of the nostril ( 4a ) was estimated , which increases with the size of the creature (from those that were taken into account in the calculations).
Elephants have the widest nostrils of all mammals studied, with a nostril radius of 10 mm at the tip to 30 mm at a distance of 90 cm from it. Using elephants as a reporting point, the scientists charted the maximum distance at which mammals, in theory, can attract objects by suction ( 4b ). For example, for cows this distance is 1 cm, and for pigs and tapirs 0.65 cm.
And the funniest part, of course. A person can also attract objects by sucking in air, although they will not be thicker than a sheet of paper, and the maximum distance for a successful trick with a chip cannot be more than 0.4 mm. Any fluctuations in the air between the chip and the nose will make the trick impossible.
For a more detailed acquaintance with the nuances of the study, I recommend that you look into the report of scientists .
Epilogue
For what one can love science, so it is for its infinity. A person is ready with immense curiosity to explore everything, from the mysterious space and the depths of the oceans to the trunk of an elephant.
In this study, scientists conducted experiments and calculations detailing how exactly the elephant manages to attract objects using suction. On the one hand, this seems to be a very simple process, but many factors are required for its implementation, from non-standard lungs to the flexible muscular structure of the trunk.
For an elephant, its trunk is both a manipulator, an environmental sensor, and a sampling tool. Elephants' sense of smell is much better than ours, and the flexibility and mobility of the trunk allows them to interact with even the most fragile objects without damaging them.
Elephants are amazing creatures that can easily be called an example of how even the seemingly strange quirks of evolution have meaning, logic and practical application.
Thanks for your attention, stay curious and have a great weekend, guys. :)
PS After reading this material, please do not try to pull chips in at home by drawing in air. It is unlikely that the authors of the study wanted you to choke when trying to portray Dumbo.
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