The ears of owls are asymmetrical, meaning that one ear is higher up on the head than another. This allows them pinpoint the sound more precisely. The sound will strike one ear prior to it hits the other, which allows the owl to better determine the exact location of sound when compared with normal ears. Additionally, the eardrums of owls are more massive than the human eardrum in relation to the size of their bodies.
Similar to humans, owls have three distinct areas within their ears. The outer ear, middle ear, and then the inner ear. The outer ear channelizes sound waves to the eardrum, which is located inside the middle ear. The eardrum oscillates in relation to the sound waves that travel through the air and transmits energy to the inner ears, which activates thousands of tiny hairs that reside within. Different frequencies of sound will be heard by different parts of the ear’s interior and trigger various hairs which help the owl create an image of the surroundings.
Owls are extremely adept predators at night, hunting prey which includes small mammals, reptiles, as well as insects. They can turn their heads up at 270°, secure onto prey, and then launch an uninhibited attack. Owls can lock onto prey making use of the sound of their location. Sound localization can be defined as the animal’s ability to determine the source of a sound’s sound in the distance and in the direction.
Three species of owls possess ears symmetrical in size and area and shape, which aids in sound localization. The species that are affected are the barn owl (Tyto alba) as well as northern saw-whet-owls (Aegolius acadicus) and long-eared Owls (Asio thetus).
Barn owls are the most studied for the ability to locate sounds (Tyto alba) since they employ similar techniques to humans in understanding interaural time difference on the plane of horizontal. The owl species has developed a special system of pathways in the brain that enable the owl to detect a sound and determine the whereabouts of the object which caused the sound. Sound waves enter the ear through the ear canal, and then travel to the membrane of the tympanic nerve.
The tympanic membrane sends those waves across the ossicles in the middle ear before entering the inner ear, which includes the vestibular organs, cochlea auditory nerve, and cochlea. They can then make use of interaural time differences (ITD) along with interaural levels differences (ILD) to determine the position and elevation that their predators are located.
Anatomy of Owl Ear :
- Owls usually have symmetrical ears and their openings located in the middle of the eye. The design of the opening called the aperture, is dependent on the species. In certain species, the ear opening has an operculum, or valve operculum, that surrounds the opening.
- Left ear opening usually positioned slightly more high than that of the right ear opening in order to help with sound localization as well as the detection of predators, even in darkness. In flight the left ear is able to receive the sounds coming from below, while the right ear is able to receive sounds from above.
- The feathers along the edge of the face of the barn owl create an oval that functions to concentrate and trap sounds, much like the human’s outer ears. The sound waves pass through the ear canal of the owl until they get to the eardrum, through the ossicles and to the inner ear, so that the owl can to know precisely the exact location of their prey.
Because owls rely upon their capability to locate prey with their super sense of hearing to survive, it’s crucial to know the structure of the barn owl’s ear that are responsible for transmitting the sound waves.
The ear canal of barn owls is comprised of the vestibular organ the cochlea along with the auditory nerve. The inner ear’s anatomy of barn owls was investigated in an experiment in which three owls were used and fixed in laboratories using in-vessel perfusion using 1% formaldehyde as well as 1.25 percent glutaraldehyde within a 0.1 buffer containing phosphate.
- The temporal lobes in the owls were removed from the skulls, fixed with the presence of 1% osmium troxide which was then dehydrated and embedded in Araldite to examine anatomical features of the ear. This study demonstrated that the basilar papilla in barn owls is distinguished by two distinct features : a proliferation of lenticular cells as well as an increase in the thickness of the membrane that surrounds it.
- The cochlear duct in the owl is home to the basilar papilla, Tegmentum, the tectorial membrane vasculum, as well as Macula of the Laga. The basilar papilla of cochlea was found to be 9.5-11.5 millimeters in length. The sensory hair cells in the proximal region contained predominantly short hair cells with some intermediary hair cells but none of the high-density hair cells. Tall hair cells are located on the distal portion of the papilla of the owl, beginning at around 5 millimeters from the proximal tip as well as a few hairless cells. The distal end of the papilla’s papilla’s papilla’ solely by tall hair cells and the proximal end is only occupied by the lenticular cells.
- Two main components that make up this basilar membrane comprise the vestibular portion and the tympanic component. The vestibular portion in the basilar membrane surrounded by supporting cells , as well as a few border cells located at the lower portion of the membrane. It is thin towards the distal portion of the papilla.
- However, it is thick and fibrous towards the proximal part. The dense fibrous mass was has been measured to be 37-57 millimeters in size in length and 8.5-11 inches in height, which is the same for the owls that were used for this study. The mass should not be mistaken for the fibrous loose mass in the tympanic portion of the basilar membrane, which forms the basis in the basilar membrane which has sensory cells covering it.
- The fibrous mass that is loose in the tympanic portion is formed near the proximal end as does the fibrous mass that is dense, however, the fibrous mass that is loose is larger and covers more that of the basilar membrane. The only thing between the vestibular as well as the tympanic components is thin, dispersed fibrous cords. These fibers’ cords can be seen near the pendulous tympanic edges of the fibrous mass loose located in the proximal region of the papilla. However, they are scattered throughout the mass.
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