Amazing Animal Senses
Visible Light Touch Sound Ultraviolet Light Temperature	Gravity	Infrared Radiation Smells Magnetic Fields Tastes Electric Fields

Some animals have developed amazing adaptations to their environments. Many different types of energy exist in the environment, some of which humans cannot detect. Here are some examples of how some animals sense the outside world and the anatomical structures that allow them to do so.
Ants	Can detect small movement through 5 cm of earth. Can see polarized light.		Bats	Can detect warmth of an animal from about 16 cm away using its "nose-leaf". Bats can also find food (insects) up to 18 ft. away and get information about the type of insect using their sense of echolocation. Can hear frequencies between 3,000 and 120,000 Hz.
Bees	Can see light between wavelengths 300 nm and 650 nm. Have chemoreceptors (taste receptors) on their jaws, forelimbs and antennae. Worker honey bees have 5,500 lenses ("ommatidia") in each eye. Worker honey bees have a ring of iron oxide ("magnetite") in their abdomens that may be used to detect magnetic fields. They may use this ability to detect changes in the earth's magnetic field and use it for navigation. Can see polarized light.		Butterfly	Has chemoreceptors (taste receptors) on its feet. The butterfly has hairs on its wings to detect changes in air pressure. Using vision, the butterfly Colias can distinguish two points separated by as little as 30 microns. (Humans can distinuguish two points separated by 100 microns.) The common bluebottle butterfly has at least 15 different types of photoreceptors in its eye.
Buzzard	Retina has 1 million photoreceptors per sq. mm. Can see small rodents from a height of 15,000 ft.		Cat	Has hearing range between 100 and 60,000 Hz. Olfactory membrane about 14 sq. cm. For comparison, humans have an olfactory membrane of about 4 sq. cm.
Chameleon	The eyes of the chameleon can move independently. Therefore, it can see in two different directions at the same time.		Cockroach	Can detect movement as small as 2,000 times the diameter of a hydrogen atom.
Crab	Has hairs on claws and other parts of the body to detect water current and vibration. Many crabs have their eyes on the end of stalks.		Crayfish	Has sensory hairs that can detect movement of 0.1 microns (at 100 Hz frequency).
Cricket	Can hear using their legs; sound waves vibrate a thin membrane on the cricket's front legs.		Dog	Has olfactory membrane up to 150 sq. cm. Can hear sound as high as 40,000 Hz.
Dolphin	Like bats, dolphins use echolocation for movement and locating objects. Can hear frequencies up to at least 100,000 Hz.		Dragonfly	Eye contains 30,000 lenses.
Earthworm	Entire body covered with chemoreceptors (taste receptors).		Eagle	Eyeball length = 35 mm (human eyeball length = 24 mm) Visual acuity is 2.0 to 3.6 times better (depending on the type of eagel) than that of humans. (Shlaer, R., An eagle's eye: quality of the retinal image, Science, 176:920-922, 1972.)
Elephant	Has hearing range between 1 and 20,000 Hz. The very low frequency sounds are in the "infrasound" range. Humans cannot hear sounds in the infrasound range.		Falcon	Can see a 10 cm. object from a distance of 1.5 km. Visual acuity is 2.6 times better than human. (Garcia et al., Falcon visual acuity, Science, 192:263-265, 1976.) Can see sharp images even when diving at 100 miles/hr.
Fish	Some can detect the L-serine (a chemical found in the skin of mammals) diluted to 1 part per billion. Have a "lateral line" system consisting of sense organs ("neuromasts") in canals along the head and trunk. These receptors are used to detect changes in water pressure and may be used to locate prey and aid movement. Some fish can see into the infrared wavelength of the electromagnetic spectrum while others, such as Sockeye salmon, can see ultraviolet light.		Fish (Catfish)	Has 3 or 4 pairs of whiskers, called barbels, to find food. The catfish also has approximately 100,000 taste buds. (Humans have only 10,000 taste buds.)
Fish (Deep sea)	Only have rods in the retina: 25 million rods/sq. mm. Perhaps they need this high density of photoreceptors to detect the dim biolumninescence that exists in the ocean depths.		Fish (Drum Fish)	Collects underwater sound vibrations with an air bladder. The signals are then sent from the air bladder to the "weberian apparatus" in the middle ear and then to the inner ear. Hair cells in the inner ear respond to the vibration and transmit sound information to the fish brain.
Fish ("Four-eyed Fish" Anableps microlepis)	Can see in air and water simultaneously. Each eye is divided by flaps, so there is one opening in the air and one in the water.		Fly	Each eye has 3,000 lenses. (Simmons and Young, 1999) Eye has a flicker fusion rate of 300/sec. Humans have a flicker fusion rate of only 60/sec in bright light and 24/sec in dim light. The flicker fusion rate is the frequency with which the "flicker" of an image cannot be distinguished as an individual event. Like the frame of a movie...if you slowed it down, you would see individual frames. Speed it up and you see a constantly moving image. The small parasitic fly (Ormia ochracea) can locate sounds within a range of only 2o of the midline. (Mason et al., Nature, 410:686-690, 2001) Blowflies taste with 3,000 sensory hairs on their feet.
Frog	Has an eardrum (tympanic membrane) on the outside of the body behind the eye.		Giant Squid	Eye is 25 cm in diameter. Retina can contain up to 1 billion photoreceptors. Sensitive to polarized light.
Grasshopper	Has hairs ("sensilla") all over the body to detect air movement. Can hear up to 50,000 Hz.		Hawk	Normal vision for people is 20/20. A hawk's vision is equivalent to 20/5. This means that the hawk can see from 20 feet what most people can see from 5 feet. (Scientific American, April 2001, page 24)
Hawk Buteo	Has 1 million photoreceptor per square millimeter in its retina.		Iguana	Able to detect the temperature of sand within 2 degrees F. This temperature is needed for the iguana to lay its eggs.
Jellyfish	The box jellyfish has 24 eyes. (Nature, 435:201-205, 2005.)		Mice	Can hear frequencies between 1,000 and 100,000 Hz. By comparison, humans can hear frequencies between 20 and 20,000 Hz.
Star-nosed Mole	Uses its fleshy star nose for hunting. The Star-nosed mole has 100,000 nerve fibers that run from star to the brain. This is almost six times more than the touch receptors in the human hand.		Mosquito	Attracted to host by human body odor (especially foot odor), carbon dioxide, body heat and body humidity.
Moth	Noctuid Moth has a hearing range between 1,000 and 240,000 Hz. Emperor Moth can detect pheromones up to 5 km. distant. Silkworm Moth can detect pheromones up to 11 km. distant. This moth can detect pheromones in concentrations as low as 1 molecule of pheromone per 1017 molecules of air. A receptor cell can respond to a single molecule of the pheromone called bombykol and 200 molecules can cause a behavioral response.		Octopus	Retina contains 20 million photoreceptors. The eye has a flicker fusion frequency of 70/sec in bright light. Sensitive to polarized light. The pupil of the eye is rectangular. Has chemoreceptors (taste receptors) on the suckers of their tentacles. By tasting this way, an octopus does not have to leave the safety of its home.
Penguin	Has a flat cornea that allows for clear vision underwater. Penguins can also see into the ultraviolet range of the electromagnetic spectrum.		Pig	Tongue contains 15,000 taste buds. For comparison, the human tongue has 9,000 taste buds. Xan smell truffles under six inches of soil.
Pigeon	With eyes mounted laterally on their heads, pigeons can view 340 degrees...everywhere except in back of their heads. Can detect sounds as low as 0.1 Hz.		Platypus	Has electric sensors in its bill that can detect 0.05 microvolts. Other receptors in the bill are for touch and temperature detection. The cochlea of the inner ear is coiled only a quarter of a turn. In man, the cochlea is coiled about 2.7 times.
Rabbit	Tongue contains 17,000 taste buds.		Rat	Has hearing range between 1,000 and 90,000 Hz.
Seahorse	Each eye can move independently.		Scallop	Has 100 eyes around the edge of the shell. These eyes are probably used to detect shadows of predators such as the starfish.
Scorpion	Can detect air moving at only 0.072 km/hr with special hairs on its pincers. Can have as many as 12 eyes.		Shark	Has specialized electrosensing receptors with thresholds as low as 0.005 uV/cm. These receptors may be used to locate prey. The dogfish can detect a flounder that is buried under the sand and emitting 4 uAmp of current. Some sharks can detect fish extracts as concentrations lower than one part in 10 billion. Some sharks sense light directly through the skull by the pineal body. The thresher shark has an eye up to 5 inches (12.5 cm) in diameter. The last three facts are from D.Perrine, Sharks and Rays of the World, Stillwater: Voyaguer Press, 1999.
Snakes	Pit-vipers have a heat-sensitive organ between the eyes and the nostrils about 0.5 cm deep. This organ has a membrane containing 7,000 nerve endings that respond to temperature changes as small as 0.002-0.003 degrees centigrade. A rattlesnake can detect a mouse 40 cm away if the mouse is 10 degrees centigrade above the outside temperature. The tongue of snakes has no taste buds. Instead, the tongue is used to bring smells and tastes into the mouth. Smells and tastes are then detected in two pits, called "Jacobson's organs", on the roof of their mouths. Receptors in the pits then transmit smell and taste information to the brain. Snakes have no external ears. Therefore, they do not hear the music of a "snake charmer". Instead, they are probably responding to the movements of the snake charmer and the flute. However, sound waves may travel through bones in their heads to the middle ear. Snakes have no moveable eyelids. Instead, they have a clear, scale-like membrane covering the eye.		Sparrow	Retina has 400,000 photoreceptors per sq. mm.
Spider	Many spiders have eight eyes. Spider can detect electrical fields in the atmosphere.		Starfish	Arms covered with light sensitive cells. Light that projects on an "eyespot" on each arm causes the arm to move.

1. John Downer, Supersense. Perception in the Animal World, Holt and Co., New York, 1988, pp. 160. (Grades 9-12).
2. Howard C. Hughes, Sensory Exotica. A World Beyond Human Experience, The MIT Press, Cambridge, 1999, pp. 345. (Grades 9-12).
3. Sandra Sinclair, How Animals See. Other Visions of Our World, Facts on File Publications, New York, 1985, pp. 146 (Grades 7-12).
4. Jillyn Smith, Senses & Sensibilities, John Wiley & Sons, New York, 1989, pp. 230 (Grades 9-12).