Senses of Animals
Humans and animals have the same sensory systems including auditory (hearing), gustatory (taste), kinesthesia/proprioception (touch), olfactory (smell), and vision (sight). However, the acuity of these senses for animals may be increased or decreased compared to humans’ senses. For example, rats and mice have a limited visual ability but their sense of smell is increased when the ability is compared to humans’. Additionally, some animal species have other sensory abilities that humans do not have such as echolocation, electroreception, infrared detection, ultraviolet detection, and whisking.
One of the most notable animal senses is echolocation, which is used by microchiropteran bats, dolphins, toothed whales, shrews, and a few cave-dwelling birds. These animals use echolocation for navigation purposes and communication as well as for hunting or foraging for food. Echolocation is a type of bio sonar. The animal will make its own high-pitched sound—above the hearing range for humans—and wait for the echo to return to its ears. In animals that use echolocation, their ears are slightly apart so that when the echo from the environment returns, the sounds are received at different time points for each ear. The auditory cortex uses this time difference to determine the distance of the object. Some blind humans have learned to use echolocation to navigate their movements by either using a clicking device or making sounds by mouth.
Electroreception is the ability to sense electrical fields in the environment. It is mostly used by aquatic or amphibious animals who live in the ocean, as saltwater is a good conductor of electricity. Recent studies, however, have shown that bees, cockroaches, and land monotremes (echidnas) have the ability to use electroreception as well. Lampreys, sharks and other cartilaginous fish, catfish, platypus (aquatic monotremes), and others use electroreception to detect their location, the location of their prey, and to communicate. In active electrolocation, some aquatic animals have a specialized organ that consists of modified muscles or nerves. This electric organ produces an electric field around the animal’s body. The animal also has sensors to detect if an object distorts the electric field. The electric field in most cases is very weak, less than one volt. Other animals use a passive form of electrolocation. They are able to detect a nearby animal’s bioelectric field in the environment by the changes of ion flow through the gills.
Infrared and Ultraviolet Detection
Some animals and insects use wavelengths that are outside of visual light, either infrared (very long wavelengths) or ultraviolet (very short wavelengths), to locate prey or food. In the cases of infrared, snakes have air-pocket pits that are covered with a membrane containing heat-sensing receptors or a pit organ. These structures are located within the head and are able to detect infrared heat to help in locating prey and to regulate the snake’s body temperature. Bees have compound eyes that can use ultraviolet wavelengths to help find flowers. Scientists have shown that when flowers are viewed under ultraviolet light, the flowers reveal a pattern we humans do not see. This helps bees to identify flowers with different types of pollen.
Many land mammals—mice, rats, cats, dogs, and others—have specialized whiskers that are necessary to detect spatial sensing such as the width of an opening or for object identification. These are called vibrissae, a Latin word meaning to vibrate. Mammals will move their facial whiskers (vibrissae), sweeping them back and forth quickly and repetitively to explore their external environment. Vibrissae are grown in groups and are located in different parts of the head or body, which may lead to different specialized tasks. Vibrissae on the head are found above the eyes (supraorbital), on the cheeks (genal), around the mouth (mystacial), and on the jaw (mandibular). Vibrissae are also found on the wrist (carpal) on the underside of the leg just above the paw. The mystacial vibrissae are divided into groups based on their size: macrovibrissae and microvibrissae. The macrovibrissae are stiff and protrude to the side of the face. These are used to detect spatial openings. For instance, if the macrovibrissae are stimulated when a cat puts its head into a small opening, the cat will know that the rest of its body would not be able to fit. In rodents, these whiskers are generally the same size as the width of the animal’s body. The microvibrissae are below the nostrils and are used to identify objects.
Patricia A. Bloomquist and Jennifer L. Hellier
See also: Pheromones; Vibration Sensation; Vomeronasal Organ
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