A book by Ed Yong, An Immense World, gives us insight into how animal senses differ from ours. I often assumed that animals were like us, but with extra capabilities, such as a dog’s superior hearing or sense of smell. In fact, we live on our planet in very different ways.
A note on this book for those who might be encouraged to read it. The book is equally fascinating, pedantic, and ponderous. I recommended this book to my book club. But most of the members of my book club were unable to finish it…and I may be banned from selecting books for the foreseeable future.
At its core, the book helps us understand how differently we sense the world. Humans are highly visual with high acuity and color sensitivity; most other species use other senses. Our vision is limited in some ways. We have better color vision and acuity than most species, but raptors and some birds have better acuity and a wider field of vision. Prey animals, with their eyes on each side, have a greater field of vision than we do…but it is blurry.
Most humans cannot see ultraviolet (UV) light (which is below 400 nm). For that reason, scientists assumed that few species could perceive UV wavelengths. But that is not true. Many animals and insects can see UV…in fact some bird species have UV markings that distinguish gender; we cannot see the differences, but they sure can. Bees use their UV light vision to find pollen and nectar in flowers that use ultraviolet markings to attract them.
The world we live in is a sensory abundance, and we all experience it differently. There are smells, sights, senses, visual and auditory wavelengths, vibrations, that we cannot sense…but they are out there. In our ethnocentric world, we are often guilty of assuming that everyone sees the world exactly as we do. But it is not even close.
Even within our human species, our vision differs, sometimes dramatically. We have different levels of acuity. We have different night vision capabilities. We have different color vision. Eight percent of the population, mostly males, cannot distinguish certain colors due to “color blindness” (the most common is red/green color deficiency). In a column several years ago, I noted that it is estimated that 12% of women have four instead of three cone cells (which are the cells that we use to perceive color). The vast majority of us are trichromats (using three cone cells that are activated at certain wavelengths). But a few women are tetrachromats, with four types of cone cells uniquely tuned to wavelengths allowing them to see millions of colors. Each of our cone cells may be sensitive to slightly different wavelengths, making it likely that we all see colors differently.
Blame these differences on the X chromosome which carries the genes for color vision. Tetrachromatic vision occurs when one of the X chromosomes has a gene for an additional cone cell and the other X chromosome has genes for three or four cone cells. Some insects and birds are tetrachromats. The most well-known are zebra finches.
Similarly, hearing degrades over time. Men lose the capability to hear the frequencies in the woman’s voice’s range. (Payback, I guess for that X chromosome vision thing.)
Because humans are so visual, it is likely that we have capabilities in other senses that have gone dormant. It is well known that bats and dolphins use echolocation (called sonar) to find prey and navigate around obstacles. I was amazed to learn that some blind individuals have developed echolocation capability.
Our senses of smell are equally diverse. To some people, body odor smells like vanilla…if only.
It is a beautiful spring day. I walk outside and marvel at my pansies representing all the hues of the rainbow; some with happy faces, others with a yellow mid-center. My climbing honeysuckle bush is awash in vermillion, tubular flowers, perfectly hued to attract hummingbirds. The trees have their early blush of pale green sponged across their branches and the vivid green spring lawn is dotted with the occasional bright yellow dandelion. My fluffy pink peonies are spreading their sweet scent throughout my garden…complementing my variegated weigela bush whose branches are laden with light pink flowers. My clematis is climbing up an abandoned birdhouse, sporting pale green buds and generous lavender flowers.
My cockapoo, Annie, is using her sense of smell to follow the trail of a bunny that dashed away after being alerted to our presence by its superior sense of smell and hearing. After reaching the end of the bunny’s trail, Annie lifts her head and sniffs at the scents from a barbecue two blocks away. She can identify all the meats on the grill and each ingredient in the barbecue sauce. Children are dancing around the barbecue squealing and laughing sometimes in frequencies that I can no longer hear.
My dog, Gus, whose hearing ability is four times greater than mine, listens for the unmistakable click of the door handle next door and rushes to the fence to await the arrival of his tail-wagging dog buddy.
Spring is awash in green hues; but my dogs can only see the blues and yellows of my smiling pansies. The green hues that I am admiring appear to them to be shades of brown/gray.
My garden is brimming with multi-colored flowers, but the bee buzzing around my yard is searching for UV markings (that I can’t discern) on dandelions to find the nectar and grab their pollen. She will be depositing some of that pollen onto the next flower that beckons her.
I can hear the caws from the greedy crows watching from above. Their superior acuity and wide angle of vision are monitoring me, to see if I’ll fill the bird feeders.
On the wires above, a bird is singing for his mate, producing two notes simultaneously in sequences so rapid that my ears cannot discern the complexity of his song.
Elsewhere, a raptor is using his visual acuity, which is ten times ours, to spot a field mouse dashing through my lawn. The mouse has poor vision, so he is using his whiskers to guide him through the weedy maze as he makes it safely through the hole that he crafted under my house. Unfortunately for him, the humongous black snake that has set up residence there uses his infrared vision to spot a thermal image of the mouse. But the mouse is aware of him. Despite the darkness, the mouse can smell the snake, hear its movements, and detect its vibrations with its feet.
Bugs that I don’t see are crawling in the dirt, using their tactile senses and scent locators to find food.
The little ants that are wandering in the lawn have poor vision so they are using their antennae to smell the breadcrumbs that fell from my bagel. They have a very keen sense of smell because they have five times more odor receptors than most insects. They are alerted to, my dog, Annie’s presence through vibrations from her steps that they can sense with their legs. Annie steps on an ant and kills it. Upon its death, it releases pheromones signaling danger causing a group of ants to arrive to investigate the cause of death. After their investigation they will return to the hive and relay the results of their investigation.
And while I am marveling at the bright sunny day and the visual splendor of the colors that are before me, the rest of the animal and insect kingdoms are going about their business, mostly oblivious to my existence. We are all living in a very large world, yet simultaneously inhabiting parallel universes.
Angela Rieck, a Caroline County native, received her PhD in Mathematical Psychology from the University of Maryland and worked as a scientist at Bell Labs, and other high-tech companies in New Jersey before retiring as a corporate executive. Angela and her dogs divide their time between St Michaels and Key West Florida. Her daughter lives and works in New York City.