Animal Senses: Peregrine Falcon

Peregrine Falcon, Mark W. McGinnis

24. Animal Senses

Peregrine Falcon

The Peregrine Falcon is one of the most famous raptors in the world. Part of that may be because it is the most widely distributed raptor in the world and only comes in second to the pigeon as the most widely distributed bird. Surprisingly, they are more closely related to parrots than hawks. But the Peregrine falcon’s fame is also due to its phenomenal dive, or stoop — more on that later.

They are not large raptors, ranging from 13” to 23” body size, 29” to 47” wing span, and females weighing 25 to 53 ounces. Males usually weigh under 25 ounces, being considerably smaller than the females. Due to their small size, the males are more maneuverable and do the more of the hunting. The size of the female allows it to carry 50% more weight and has a faster stoop. They mate for life, and the male does dazzling aerial acrobatics in the courtship. They make their nests on cliff shelfs or skyscrapers, have 3-4 eggs, and ferociously defend the nest, and yet only about a third of hatchlings survive. When bringing home a kill for the chicks, the female may fly upside down under the male and take the meat from his claws. They hunt primarily at dawn and dusk; their primary prey is medium-sized birds taken in flight. The life span of a Peregrine falcon is around 15 years.

The falcon’s super sense is its eyesight. Instead of the single fovea (a depression in the retina where visual acuity is the highest), the Peregrine falcon has two fovea in each eye, 33% more cones, and twice the visual acuity of humans. They also have a shallow fovea that focuses forward and gives sharp distance information. The deep fovea focuses laterally, taking in closer information to the sides. This dual binocular vision allows the falcon to focus on two or three places simultaneously. It has the highest spatial resolution of any animal. This super sight also allows the falcon to see prey over a mile away.

This eyesight gives the Peregrine falcon the capacity for the previously mentioned — famous stoop. Other raptors dive to capture their prey, but not at the astonishing speed of Peregrine — over 200 miles an hour. They are the fastest animals on earth. The dive can begin at a 1000-foot altitude, and the bird turns into a torpedo shape that cuts through the air. The bird has adapted to meet the demands to accomplish such a feat. Its eyes have a third eyelid that keeps them moist and protected from the intense rush of air against the eye. Below the eyes are dark patches of feathers that reduce the solar glare (like athletes). The dark patches are larger in parts of the world with much strong light. The rush of air on the head also causes blasts into the nostrils, strong enough to damage the lungs. To avoid this, they evolved cone-shaped baffles in their nostrils to slow the air down. It is said the baffle system of the Peregrine inspired early jet engine design to solve the same problem. Their overall shape is one of flying perfection.

When the falcon makes its blazing dive, it also endangers itself. A crash into the prey could injure the predator more than the prey. Instead, the Peregrine makes a fist of one of its large lethal feet, punches the bird in the wing, and breaks it. When the falcon ends the stoop he may have reached 25 G-force (twenty-five times the normal gravity we experience). The average person can endure only 5 G. The falcon may then turn to the prey, grab it with its formable talons, and take it back to the nest, or another safe place to eat. It may also let the bird fall to the ground and grab it there. To kill, they often use a “tooth” on their beak that severs the spine cord behind the skull — a quick death.

With everything written above, one would assume that not much could escape this incredible predator. Well, it is almost the opposite. Peregrines have a 20% kill rate —eight of ten get away. The stoop attack probably has a higher percentage, but it is not the only way they hunt. They often use the traditional horizontal chase, but now their prey has a much greater chance as they have all their talents to use. To be fair, it has been observed that not all peregrine attacks are to kill, but sometimes to play or practice — I’ll bet they don’t tell the pigeons it’s play.

Animal Senses: Pit Vipers

Pit Viper, Mark W. McGinnis

22. Animal Senses

Pit Vipers

There are 150 species of pit vipers in temperate and tropical areas around the world. The USA has three species, with rattlesnakes being the most numerous. Pit vipers can range from 18 inches to 8 feet long and live 10 to 25 years. The females breed once every three to five years. Males compete fiercely for mating rights. They will travel as much as five miles a day during mating season looking for a female. When a mate is found, there may be other males already fighting. They twist, tangle, rear up, topple each other, but do not bite one another. The victor copulates with the female for hours or days; on completion, he may place a copulatory plug in the female to inhibit the success of other males. Defeated males sometimes go into what seems a state of depression. A few pit viper species lay eggs, but most develop eight to ten membranous eggs within her and giving live birth when they have hatched. The young are self-sufficient at birth.

Vipers eat primarily rodents and small birds. They are important in the ecosystem, keeping the rodent population in balance. Pit vipers are ambush hunters and wait for prey to pass by and attack. They strike their target with a bite and inject venom, which usually doesn’t kill but gradually immobilizes the creature and begins the digestive process. The snake follows the fleeing animal by its scent, swallows it whole, and begins a digestion process that can last days to weeks. The snake eats about once every two weeks. They are not aggressive animals and do not strike out, if not hunting unless they are startled, cornered, or some fool provokes them. Humans receive about 7,000 – 8,000 venomous snake bites a year in the U.S., and of those, about five people die (due to modern medicine). Of the U.S. pit vipers, the rattlesnake has the most dangerous bite. It is extremely painful, can cause the destruction of tissue, cause permanent paralysis or loss of a hand or limb, cause internal bleeding, and create dangerously low blood pressure. If bit, don’t try silly methods such as sucking out the venom; wash the wound, cover it, stay calm and rest, and immediately seek medical care. Dogs and cats receive 150,000 bites annually; fatality rates range from 1% to 30%. The pet is often attacking the snake, not realizing that the snake’s lunge is much faster than theirs. When living in the southern Black Hills of South Dakota, I had a neighbor whose dog was bit six times — he was not a fast learner.

The pit viper’s senses are finely tuned to fit its lifestyle, and it has not five but six senses. The animal’s vision is not overly acute, with limited color and distance refinement, but a sharp capacity to see movement. It’s hearing/tactile sense is feeling vibration with its long body. It can sense the slightest vibration around it, such as a mouse’s footsteps. The pit viper’s first super sense is that of smell/taste. This is accomplished primarily through its long forked tongue. As scary as that flicking tongue appears, it is only gathering molecules that give the snake detailed information. It can move the tongue in various directions and patterns, collecting environmental data. The split tongue provides the viper with “stereo-smell.” The tongue comes back into the mouth, and tips are inserted into two holes in the Jacobson’s organ on the top of the mouth. From there, the molecular/chemical information is sent to the olfactory area of the brain, where it is analyzed and stored for future reference.

The sixth sense is the most extraordinary of them all. Pit vipers are so named for the pits they have on each side of their heads between the nostrils and the eyes; they are called loreal pits, and with one on each side of the head, they again receive stereo thermal information. The prey’s direction, distance, and size is determined. Detailed knowledge of the heat around the snake is collected and calculated. On its way to the brain, it is combined with visual information and heat, and visual maps are overlaid in the brain. This map gives precise images of warm-blooded creatures and their background. It is an exceptional tool to find prey even in total darkness and to be aware of predators they wish to avoid.

Most people do not like snakes, but it is more than “do not like.” Fear would be more accurate, and with some people, phobic anxiety. It seems likely that this is an evolutionary tendency — “For your own safety, stay away from snakes.” This is still good advice with pit vipers. Give them ample space and let them go about their fascinating and valuable lives.

Animal Senses: Hummingbirds

Hummingbird, Mark W. McGonnks

21. Animal Senses

Hummingbirds

Everything about hummingbirds is amazing. Here is a short list:

– Oldest fossil is 30 million years old

– Evolved to fit flowers

– 336 species in the Americas, 15 in the U.S.

– Smallest mature bird

– Weight ranges from 0.07 to 0.70 ounces

– Flap wings 12-80 beats a second

– Have the highest mass-specific metabolic rate of any thermally regulated animal

– Heartrate is 1,200 beats a minute

– 250 breaths a minute

– Consumes the human equivalent of 150,000 calories a day

– Can lick nectar 10-15 times a second

– Only a few annually migrate, but they can travel 500 miles a day (experts at catching tailwinds), can fly 20 hours a day; the longest migration is 3,000 miles

– Have been known to fly at an altitude of 14,000 feet in the Andes mountains

– Live from 3-5 years, a few up to 9

Now, that is amazing (I double and triple-checked those numbers). To slow hummingbirds’ manic metabolic rate, at rest, they go into a tophor, where they can reduce the rate to about a fifth. They are primarily nectar eaters but also eat insects and spend 70-80% of their time resting and digesting. Some bird’s aggression at feeders may be due to mate competition and an instinctual drive to protect food sources, as starvation is a real threat to hummingbirds.

Hummingbirds supersense is its vision. It sees the spectrum of colors we see, plus ultraviolet, but it also sees a range of non-spectral colors. These are ultraviolet + yellow, ultraviolet + green, ultraviolet + red, ultraviolet + blue, and ultraviolet + purple. How a field of wildflowers looks to a hummingbird is beyond our comprehension. The hummingbird’s brain has an enlarged area for vision and makes comprehensive memory maps for foraging. Its cornea occupies 50% of the eye diameter and is packed with neurons. They have both lateral and binocular vision, giving them an incredible 340-degree field of vision. Hummingbird flight is a wonder to watch. To execute their acrobatics at such speed requires precise vision. I am an avid hummingbird watcher, and I have never seen them make contact with anything or each other unless fighting or mating (the beak/sword fighting is something to behold, as is the figure-eight courtship flight).

Hummingbirds have a sharp hearing. They make a wide range of vocalizations for social interaction. They can hear tonal changes we can’t and also communicate with changes in the humming of their wings. Birds cannot taste sweet; that is, all birds except songbirds and hummingbirds. They evolved their savory taste receptors to detect sweet instead. For a long time, it was thought that hummingbirds had no sense of smell (that seems strange to me and is still found on the internet and in some texts). They do have a sense of smell that aids in foraging and also alerts them to danger. They can smell chemicals that alert them to the threat of potential predators.

The above information partially explains why hummingbirds are such a beloved and watched bird. Feeders for the birds are common in much of their range, but please remember, only plain white sugar (one part sugar, four parts water) and no coloring.

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Animal Senses: American Crocodiles

American Crocodile, Mark W. McGinnis

20. Animal Senses

American Crocodile

Crocodiles! They look like they walked straight out of the Jurassic Period some 200 million years ago. The American crocodile is scary-looking and big, averaging 12-14 feet (a few up to 20 feet) and an average weight of around 1000 pounds. They aren’t picky eaters, consuming what is in the water, feeding in the water and on the banks. Fortunately for us, they are quite shy of humans and usually retreat. I said usually, they have taken people, and big ones have been known to take cows. They live 50-70 years in the wild. The primary way to tell crocodiles from alligators is that they have a longer snout, and their body color is a lighter gray.

An unexpected aspect of crocodiles is the females’ maternal instincts. She digs a nest along the river and lays 30-60 three-inch eggs. She then buries the nest, and this is the tricky part. The nest’s temperature needs to be close to 89 degrees to balance male and female hatchlings. If the temperature is higher, most will be males; if lower, mostly females; if 82 degrees or lower, the eggs won’t hatch. The nest must be made precisely and oriented correctly with the sun. The female ferociously defends the nest. The eggs incubate for around 75 days and begin hatching. The hatchlings start calling and the female diggs the nest out. If some eggs don’t open, she takes them in her mouth and gently breaks them. She then puts them all in her mouth and takes them to the river. Within a couple of days, the hatchlings are hunting. The mother usually stays around, attentive to their needs and giving them rides on her back. At five weeks, the hatchlings disperse, and predators eat most.

Crocodile senses are extraordinary. Their sense of sight is acute. Crocodile eyes have vertical pupils, as do many night-hunting animals. The vertical pupils can regulate the light coming into the eye better than a round pupil. This is helpful in the daylight, where too much light could damage the eye. They have another common nocturnal vision quality. They have a reflective coating behind the retina that captures light that may have missed the retina and sends it back, doubling their night vision. This is also what gives the scary glow to the eyes at night. They also have a third eyelid that protects the eye underwater. Their hearing is well developed, with slits near the eyes and flaps that cover them underwater. They can regenerate hair cells in the ear and have no hearing loss with age. Scientists are studying this. Crocodiles have an extensive range of sound frequencies, from ultrasonic to subsonic, and may also vocalize in that range. Smell is a strong sense for them with olfactory receptors in their long nasal passages. Above water, they can smell some prey for miles. Not much is known of their sense of taste, but they do fondle each other with their mouths during mating.

Crocodiles’ super sense is their sense of touch, or more precisely, their ISO, integumentary sense organs. These bump/pits are attached to nerve endings found dappling the body and clustered around the mouth. As embryos, these develop before the scales. These organs are actually multisenses. ISOs are pressure sensors, mechanosensors, vibration sensors, temperature sensors, and chemical sensors; one of the greatest arrays in the animal kingdom. Their sensitivity is so great that they can detect one drop of water entering a pool. Underwater hunting can be done with these sense organs alone.

The extreme fear of reptiles is called herpetophobia. While most people don’t have a full-blown phobia of reptiles, many have a strong dislike. Mythology, folklore, and religion have all predisposed us to fear them. Fear, disgust, and contempt are common among people, regardless of age, gender, or profession. But as shown above, American crocodiles are fascinating creatures, but giving them plenty of personal space is good.

Animal Senses: Honey Bee

Honey Bee, Mark W. McGinnis

19. Animal Senses

Honey Bees

I can think of nothing about honey bees that is not fascinating. Of the 20,000 known species of bees, honey bees make up only eight. They are found in almost all climate-friendly regions of the planet, and much of that range is because humans have moved them there for the many benefits of this creature.

They are eusocial creatures living in colonies, sometimes called superorganisms, controlled by a queen. The colony has up to a thousand male drones born from unfertilized eggs and tens of thousands of female workers born from fertilized eggs. The females are genuine workers. When young, they care for the larvae, feeding them the royal jelly they produce and pollen and honey. They keep the hive fastidiously clean, and all the bees poop outside the hive except the queen, who is busy laying 3,000 eggs a day. As the females mature, they change to jobs such as hive\cell building, guard duty, and finally, living out their lives as foragers. On a single foraging trip (beating her wings at 200 times a second), she may visit 50-100 flowers and make about eight daily trips ranging from half a mile to three miles — busy as a bee. The worker bees live from six weeks to six months.

Male drone honey bees play a limited role in the hive’s life, but an essential one. Very lucky(?) ones fertilize the virgin queen. But other than that, not much. They do no foraging, but young females feed them nectar. Drones do no work other than help regulate the temperature of the hive. If they get that one in thousands chance to mate, they die immediately as the queen rips their genitals from their body as she flies away. Their average lifespan is between 30 and 55 days, and the drones left in hive in the fall are kicked out to prepare for the more challenging conditions of winter. This minimal role of males in these super-sophisticated colonies may have significantly contributed to their success.

When a new queen is needed for the hive, the nurse workers feed female larvae only royal jelly, and the larvae develop into a queen. The virgin queen takes flight to find a place of drone congregation area where thousands, up to 20,000, males from many colonies are waiting for her. She mates with 10-20 drones and returns to the hive with enough sperm to last a lifetime. The average lifespan of a queen is two to three years.

Bees’ senses are finely tuned. They have two large compound eyes with thousands of lenses and three ocelli eyes with single lenses. Their color range is similar to humans’, slightly shifting to orange through ultraviolet. The ocelli eyes are found between the eyes and process polarized light and patterns assisting the bee’s navigation. They process visual information five times faster than humans and have excellent color and shape memories. They have a good sense of taste with taste sensilla, nerve cells, on their antennae, legs, and mouthparts. Their tactile sense is found all over the body and also concentrated in the antennae, playing an essential role in the darkness of the hive. Related to the tactile is the honey bee’s sense of “hearing.” They hear through vibrations at low frequencies. Their premiere sense is smell — olfactory. It is 100 times better than humans and is primary in communication and social order. So sensitive is their smell that bees have been trained to detect cancer cells. The queen’s pheromones do much to control the social order and tasks of the hive. However, the five senses were not adequate for the bees’ needs. They can also sense the earth’s magnetic field and some electrical fields, which give them knowledge of changes in the weather. The magnetic sense helps them navigate foraging and properly orient their hives.

A wonderful example of a fusing of these magnificent senses is the “waggle dance.” When a foraging bee has located a good source of food, she may return to hive and share its direction, how far away it is, and what quality it is. It does so in the dark of the hive, dancing in the dark, so visual information is not paramount. The bee dances in a figure-eight formation with waggling (twerking) movements at points in the figure, making a map of the food source. Other bees huddle around and absorb the information through vibration, sound, touch, pheromones, and some think magnetic information. To test this, scientists glued magnets to the bees’ abdomens and set them out after a dance. Sure enough, the bees were disoriented, or maybe they were just pissed because someone glued a magnet on them.

The above is the tip of the iceberg about honey bees. They are true wonders.

Animal Senses: Horses

Horse, Mark W. McGinnis

17. Animal Senses

Horses

Horses evolved about 50 million years ago. They have been domesticated for the past 6,000 years. That means for around 4,994,000 years, horses’ senses were developed solely to best serve them as grazing animals pursued by predators. They have the same five senses humans have, yet they have evolved quite a different Umwelt, sensory world, with those same five senses.

Horses have the largest eyes of any land mammal. They are lateral-eyed, one placed on both sides of the head. This gives a 350-degree range of vision, but the 10% it cannot see is consequential. Horses cannot see directly in front of them, so they need a slight head shift to see there. The second blind spot is directly behind them, making them skittish when something is coming up from behind (such as a person). Their day and night vision are both well-developed. They have dichromic color vision, giving them a world of greens, blues, and yellows. They can detect even the slightest movement, preparing them for flight, fight, or forage. Their eyes adjust slowly to strong changes in light intensity (such as stable lights being turned on in the dead of night), and they generally prefer dim light.

Hearing is a finely tuned sense for horses. To receive the sound, they have ears with 16 muscles that they can twist and turn, giving the horse near 360-degree sound reception without moving its head. They can hear frequencies 1300Hz above our hearing but cannot hear some low frequencies we can sense. Astoundingly, they can hear your heartbeat from four feet away and distant sound as far as 2.8 miles away. With this acute sensitivity, they don’t like loud, intrusive sounds like rock music being played in the stables. They prefer quiet music or nothing. In one “experiment,” talk radio was played continuously in the stable, and the rate of gastric ulcers in the horses (and maybe people) increased markedly.

Horses have an exquisite sense of touch. A tiny fly can light anywhere on its body, and the horse is aware. Touch is essential in their social relationships, with the grooming of other horses and muzzle touching (handshakes) being significant factors in the harmony of the herd. A bite on the butt can also send an unpleasant tactile message. Their most subtle sense of touch is their whiskers growing around their face. Each whisker is supplied with blood and nerves to take a tactile reading of anything it touches. The whiskers can be valuable in sensory experience in the dark and the blind spot in front of them. In some equine circles, trimming horses’ whiskers for cosmetic reasons has become the fashion. This practice can lead to confusion, stress, and an increased chance of injury to the horse. The practice has been banned in Germany, Belgium, and in many international equine associations.

A horse has a long nose, and that space is put to good purpose. When a horse breathes in copious amounts of air being sent to its large lungs, all along the nasal passage, the air is thoroughly scanned for odors. The receptors send the information to a large, well-developed olfactory bulb in the brain for analysis and storage in memory. Under the nasal cavity are more olfactory organs called Jackobson’s organs. They primarily receive pheromone information. When a horse curls up its upper lip and lifts its head, the Flehems response, the horse sends an unusual scent on a quick trip to Jackobson’s organs for analysis. This information is highly valuable in social relations and may explain why horses can readily read human emotions.

Most horses can be picky eaters, carefully choosing which plants to eat while grazing. They have the ability not only to taste but also to determine the nutrient value of the food. This also gives them the ability to avoid most poisonous plants.

The next time you walk up to a horse (and you certainly should — they are magnificent beings), think about the sensory array the creature has aimed at you and how much s/he already knows about you.

Animal Senses: Earthworm

Earthworm, Mark W. McGinnis

16. Animal Senses

Earthworms

Earthworms! What senses could those eyeless, noseless, earless, slimy little tubes have? Well, they could and do have a lot of senses. They have been around a few hundred million years and range from 1/2″ to 9′ 8″ (yep, really big earthworms) — the average being 4″ to 8″. They live from one to eight years, and their deceptively simple shapes have complex systems within and without. They have a double tube structure, breathe through their skin, and have lubricating pores to moisten them. They are hermaphrodites, with each individual having both female and male sex organs. When they mate, each worm inseminates the other, fertilizing the eggs of the other. The worms have 100 to 150 segments (a “saddle” segment is near the middle ) and are propelled by muscles and setae, tiny bristles on the bottom of their body. On the inside of the earthworm, their digestive system extends from the mouth to the anus creating high-quality fertilizer. They have five pairs of “hearts,” more accurately aortic arches, that keep blood moving through their circulatory system. Their brain is a cerebral ganglion of two pear-shaped organs joined at the center. With this rudimentary brain, it was often thought that they had little capability for thought. This has been proven not to be the case. They can think and make decisions. This was shown by none other than Charles Darwin. Earthworms like to disguise and block the entrance of their burrows with leaves. In his experiment, he showed that the worms consistently would drag the leaves into the hole with the tipped end first to facilitate the easier drawing of the leaves to plug the opening.

The brain is connected to the central nervous system, and nerves go to the worm’s surface. Here is where we have the remarkable senses of the earthworms. While they have no eyes, they can sense light. They have photoreceptors, called “little eyes,” on their body that tell them of the intensity and duration of the light around them. They are primarily nocturnal animals as the light can dry their skins, and ultraviolet light can kill them. Earthworms also have epidermal receptors over their bodies that give them detailed tactile information of their surroundings and the earth’s temperature. They have chemoreceptors that provide them with knowledge of taste and smell. And finally, the worms have mechanoreceptors that can sense pressure and movement — quite an array of sensory information.

As a boy, I remember being told earthworms cannot feel pain when I was taught to thread a worm on a fishing hook. That is a long-held mistruth. They certainly can feel pain. When you pick up a worm, the salt on your skin sends pain through its body, and when you run that hook through its internal organs and nervous system, it feels intense pain. Another myth is that if you cut a worm in two, the two halves will regenerate into two worms. Sometimes, the worm can regenerate the back end of its body if the cut is behind the saddle.

There are about seven million earthworms for every one of the eight billion people on the planet. They aerate the soil, improve water drainage, recycle nutrients, aid soil structure development, create high-quality fertilizer with their droppings, and more. Aristotle called them the intestines of the earth. The importance of earthworms to the ecological structure of the earth cannot be overestimated. Charles Darwin, whose final book was on earthworms, wrote, “It may be doubted whether there are many other animals that have played so important a part in the history of the world than these lowly organized creatures.” Should earthworms perish from the planet, most other life would perish.

Animal Senses: Naked Mole Rat

Mark W. McGinnis

18. Animal Senses

Naked Mole Rats

Naked mole rats aren’t rats or moles or hairless. They are rodents. Some people consider them the ugliest creature they have ever seen — saber-tooth, poorly-made sausages. What they are is one of the most incredible creatures on earth; or I should say, under the earth. These East African rodents are about the size of mice and live in colonies up to 6 feet under the ground, in tunnel systems up to 2 1/2 miles long, with multiple branching levels. They have chambers for sleeping, food storage, and latrines. These colonies have up to 300 rodents and are eusocial; they are highly cooperative communities, and a “queen” is the sole fertile member of the colony. When a queen dies, the competition/battle for the position can take weeks, and when one is triumphant, her body length extends by a third to accommodate large litters of pups. Unlike insect eusocial colonies, the naked mole rat queens do not repress reproduction in other females with pheromones but with intimidation. They cause so much stress in other females their reproductive systems switch off. The queens do not go through menopause and can reproduce the rest of their 20-30-year lives. One queen produced over 900 pups in her life. The members of the colony care for the young, dig tunnels, gather roots, and defend and plug tunnel entrances from predators, primarily snakes. The crowded colonies cause extremely low levels of oxygen and very high levels of carbon dioxide; levels would kill or brain damage most mammals.

Their exceptionally long lives and the rarity of age-related diseases, including cancer, have stimulated considerable scientific research. Naked mole rats also develop extremely little plaque or tangles in their neurons. They are playful creatures who wrestle, play tug of war, and have some rudimentary tool use. They patch the areas of roots where they eat with dirt so that the rest of the tuber will remain healthy and grow. Their large incisors are used for digging, and their lips are behind the teeth to block earth from entering the mouth. A quarter of their muscle mass is in their jaws.

Their senses have evolved to support their success in the underground environment. Living in complete darkness, they have lost all the ability to see, except for slight changes in light and dark. They hear little in higher frequencies but some lower frequencies quite well. They are quite talkative, with around 18 vocalizations, and each colony has a distinct dialect learned in adolescence. The dialects can change when a queen dies, and a new one takes power. Taste is highly developed in naked mole rats, aiding them in foraging and avoiding poisonous plants. Used in the same endeavors, they have an acute sense of smell. The olfactory area of the brain is enlarged to support this keen sense. Smell is a primary tool in social interaction, recognizing individuals, and taking social cues. The rodents roll in their latrines to have the scent of the colony and set themselves apart from an invading mole rats from another colony. They are very xenophobic.

Naked mole rats’ most highly developed sense is touch. On each side of their body, they have about 50 whisker-like, nerve-laden vibrissae that give them full-time tactile information about their surroundings. They have more facial whiskers than many mammals to help them navigate. A fascinating tactile aspect is what they don’t feel. Adult rodents do not feel pain or not much. Their skin nerve endings have evolved to not send the expected pain level to the brain. This, again, has researchers scrambling for understanding and possible medical applications.

Naked mole rats are a good reminder of the old adage, “Don’t judge by appearances.” They may seem repellent to some, but they are critters of wonder and mystery.

1. Animal Senses — Jumping Spiders

Jumping Spider – Mark W. McGinnis

1. Animal Senses

Jumping Spiders

There are around 6,000 known species of jumping spiders. They range from 1mm to 25mm (about an inch). They range in color from mostly brown to a rainbow of reflective color. They are found in a huge range of environments, from the tropics to the slopes of Mount Everest. Evolving around 50 million years ago, it is a very successful little critter in its remarkable adaption to changing environments and developing remarkable sensory tools to make that success possible.

Independent of size and color, all jumping spiders have the standard eight legs of all spiders, an abdomen, a head, two “arms” in front, and colorful appendages in the front of the head that house powerful fangs that produce venom to paralyze their prey. Their abdomen and legs are dappled with bristling hairs, and they have eight eyes, yes, eight eyes. With that description, one would not think it, but many people find them “cute,” primarily due to their large frontal eyes.

A jumping spider’s eyes are only part of its remarkable sensory showcase, and it is a mind-blowing part. As mentioned, they have two large front-facing eyes and three eyes that wrap around each side. These eyes give the spider nearly 360-degree vision around them. They are lensed eyes similar to ours, not some insects’ faceted eyes. The three eyes on each side do not see in great detail and have minimal color, but they detect the motion of both prey and predator, and the spider can quickly turn its head and focus the two large frontal eyes on the movement. What the spider then sees is a whole different story. As we do, it has red, blue, and green vision, and ultraviolet as a bonus. They see this colorful abundance in nearly HD crispness.

It wasn’t known until recently how and if jumping spiders could hear. They have no ears or ear drums. In an announcement that startled many scientists, it was found that jumping spiders hear with the hairs on their legs and body. The sensitive hairs respond to movements of air that accompany the sound. That is really sensitive hair. They can “hear” sounds from as far away as sixteen feet. Just as incredible is the spider’s sense of taste. It has chemical sensors on its feet, which is how it “tastes.” It tastes everything it walks on.

The male’s mating dance is as remarkable as its senses, and he uses his senses in amazing ways. It is a stylized series of gestures and movements, throwing his long legs in the air and twitching his abdomen. It must be a great dance, and the female approves, or she might eat him. Sometimes, she eats him after mating. It seems that the males of many species will do crazy things for the opportunity of mating.

They rarely build webs but are stalking prey hunters ranging from insects, other spiders, worms, and larvae. They do use the silk they produce for beneficial purposes. They build tents for bad weather, to sleep in, and to winter in. They also often leave a trail of silk behind them to be used as an escape rope to swing away on and also use the silk strand to swing into areas they cannot access in other ways.

Looking back at the sensory information I have given above, I cannot think that an alien could step out of a flying saucer and be more different from these little spiders. Undoubtedly, we know only a fraction of what their sensory experience is. The sensory bubble that jumping spiders live in is their Umwelt. It is their unique world.

2. Animal Senses — Vampire Bats

Vampire Bat — Mark W. McGinnis

2. Animal Senses

Vampire Bats

Vampires!! Bram Stocker! Bela Lugosi! Ann Rice! Buffy! Twilight! Lost Boys! Dark Shadows! Count von Count! Count Chocula! (Well, the last two aren’t very scary.)

Vampire bats are primarily social creatures living in roosts of 20 to 100 individuals, but occasionally in the thousands. The females only produce one offspring a year and sometimes share in caring for the young of others, especially orphans. The females will often maintain relationships with each other for years. They are clean animals and do considerable self-grooming and social grooming. If a group member has not been successful in the hunt, others may regurgitate food for them. Vampire bats’ usual lifespan in the wild is nine years.

They are exceptional hunters. Echolocation, emitting high-pitched sounds that echo back to them, shows shape, location, distance, and speed in incredible detail. It is a formidable tool that very few land mammals share. They have excellent eyesight, primarily monochromatic, as little color exists in the darkness where they live and hunt. Vampire bats can see up to 500 feet in near-total darkness. Their sense of hearing is acute, and they possess a highly developed sense of smell to find prey and to recognize roost mates.

Their diet causes a primary repulsion people have for vampire bats. They eat only blood and are the only mammals to do so. But blood is not a good food source, having few calories and little fat and carbs. This requires the bat to feed daily; if they fail to find food two days in a row, they will likely die. To gain sufficient nutrition, the bat must consume about half its weight in blood daily. This sounds horrific, but the average weight of a vampire bat is one to one and a half ounces. The bat takes a tablespoon of blood in a feeding. Many folks think of vampire bats as large, fearful creatures, but their head and body together are two to three inches, and their wingspan is eight inches.

Vampire bats primarily feed on livestock. After it finds its sleeping prey using its fine-tuned senses, it usually lands on the ground. From there, it can walk/run using its wing thumbs (claws). It then delicately crawls up the beast and searches for a good place to feed. When gently crawling across its food source, another of the bat’s remarkable sensory adaptations comes into play. Its nose has heat-detecting molecules and detects infrared thermal radiation. With this sense, it can find the best veins near the surface. When the vein is located, a 1/8″ incision is made using the bat’s teeth, which have no enamel to keep their razor sharpness. The bat does not suck the blood but laps it. Vampire bats have anti-clotting saliva that keeps the blood flowing. Some scientist/humorist named the substance “draculin.”

While the few tablespoons of blood an animal might lose a night does it no actual harm, the incisions the bats make can become infected, and the bats have been known to transmit rabies. Vampire bats are considered dangerous pests by livestock producers. The proliferation of cattle raising in South America has led to an increase in the bat population.

It is unlikely that my description of vampire bats’ feeding habits has endeared them to many readers, but it gives a glimpse into their Umwelt — their sensory world. The nuanced evolution of these creatures is remarkable, and while it is a bit creepy, I admire these furry, flying, blood-lapping wonders.