Some Features Of Breathing, Smell And Hearing In Dogs

2023 Author: Molly Page | [email protected]. Last modified: 2023-11-27 22:49

Research into the olfactory orientation of animals has prompted the need to study nostril function in dogs. In the available literature, it was not possible to find a description of the morphological features of the initial section of the upper respiratory tract and the movement of air in them in dogs. Only in the works of S. A. Korytin is an assumption made about the role of the lateral nasal openings in the olfactory orientation of predatory animals, which make it possible to catch odor particles brought by a side wind. However, the author did not engage in special studies of the function of these formations.

Experiments on the study of this function gave the following results. In large dogs, the cross-section of the jet of air inhaled through the nose is like an enlarged copy of the dog's nostril and resembles a tennis racket or tadpole. With a normal inhalation, the stream of inhaled air is felt at a distance of no more than 5.8 cm; when sniffing - at a distance of 7.7 cm from the nostril; when exhaling - at a distance of 17.3 cm.

With a regular inhalation, 47 percent of the air enters the nose through the side cutout, and when sniffing, a little more - 53%. When exhaling, less than 1/3 of the exhaled air passes through the side cut of the nose, that is, unlike inhalation, the bulk of the air is exhaled through the round part of the nostril.

The contours of the jets of air inhaled by both nostrils are in the plan two fans or an almost complete disk, from which two sectors, as it were, are "cut and removed" - one in front, the other behind. Directly in front of the animal's nose there is an area from which air is not sucked into the nostrils. This sector is approximately 60 degrees - 30 degrees to the left and right of the longitudinal axis of the head. In sectors from 30 to 80 degrees to the left and right of the axis of the head, air enters the round part of the nostril, both during normal inhalation and when sniffing. In sectors from 80 to 130 degrees, air enters through the lateral incision of the nose during normal inhalation, and when sniffing, these sectors extend slightly more - from 80 to 150 degrees. The enlargement of the sector when sniffing is facilitated by the function of the side cutout of the nose.

Other animals, such as horses, have approximately the same shape of nostrils. However, in horses, the “tadpole tail”, which is capable of expansion, serves to increase the entrance to the nasal cavity when breathing increases due to physical exertion. In dogs, however, any intensity of physical activity does not affect the size of the entrance to the nasal cavity (does not increase it). Here, there is an increase in the frequency of breathing with obligatory mouth breathing. Therefore, it seems that the lateral incisions of the nose in dogs are an important adaptive tool for more successful orientation in space using the sense of smell. Their structure and function contribute to the entry of air into the nose not only in front of the animal, but mainly from the side and even somewhat behind.

During normal inhalation, the fan covers two sectors of 100 degrees (from 30 to 130 degrees) to the left and right of the longitudinal axis of the head. In this case, although the animal is not alert, the function of the nostrils provides an examination of the space from the front and from the side. The upper and lower walls of the side cutout are parallel to each other, which probably prevents air from entering the nose from the rear hemisphere. When sniffing, the side cutouts change their shape. The upper and lower walls become concave, the outer slit narrows and the lateral cut in this case is a tube almost closed along its length with a narrow longitudinal cut. This state of the sidecut allows the dog to capture air portions from the rear hemisphere in the nose. The jets of inhaled air in this case are two sectors already 120 degrees (from 30 to 150 degrees) to the left and right of the longitudinal axis of the head. This is probably biologically justified, since here most of the space on the sides of the animal's head is examined using the sense of smell, without the need to turn the head to the sides.

The plane drawn through the contours of the inhaled jets of both nostrils makes an angle of about 30 degrees with the axis of the head. And the side notches of the dogs' nose have the same direction in relation to the axis of the head. Other representatives of the order of carnivores, for example, cats, also have side notches of the nose, but they are relatively small and directed along the axis of the head, and not at an angle to it. At the same time, it is known that sense of smell plays a lesser role in the life of felines, and there are no long-term, active pursuers of the victim by its scent trail among cats.

Observations of the dogs following the trail using the lower sense show that the plane drawn through the lateral incisions of the nose of both nostrils is strictly perpendicular to the earth's surface. This is biologically justified for the following reasons. If we conventionally take a stream of inhaled air for a disk with a diameter of 14-15 cm (the sensation of inhaled air when sniffing at a distance of 7.7 cm), then a dog with a muzzle lowered to the ground examines a horizontal column of air, which is a cylinder of 14-15 cm, equal to the length of the track of the pursued animal or person.

Naturally, during oral breathing, the diameter of the studied air column will be significantly smaller due to a decrease in the size of the jet of air sucked into the nose. Under natural conditions, when air masses are constantly moving, this column of air will constantly be enriched with odor information outside it. Observing the dog following the trail using the lower sense shows that the nose of the dog is approximately 6-7 cm from the surface of the soil or vegetation during movement.