by Kathleen Keefe
As the light fades, the familiar daytime creatures of High Park change places with the nightshift. The darkness is inhabited by a new cast of crawlers and creepers, flyers and leapers, howlers and beepers! Preferring the cool cover of darkness, out come the nocturnal hunters, grazers, foragers and scavengers.
These night shifters have evolved and adapted to succeed without illumination. Let’s see how these superstars of the night use their specially developed senses to navigate, communicate, eat, seek shelter, find mates and elude predators.
Night Owls
People who stay up long into the night are called “night owls.” Yet people are nowhere near equipped for nightlife the way owls are. High Park in the dark features the haunting trill of the tiny screech owl and the legendary hoot of the great horned owl. But when in flight, the owl’s prey, its predators and you will not hear its approach because the tips of its serrated flying feathers ensure nearly silent wing flaps. And while we can’t hear them approaching, their own hearing is so acute, they can locate creatures moving under heavy vegetation or snow 20 metres away! The owl’s ear openings are on slightly asymmetrical levels on either side of its head, enabling it to convert the two different incoming sound perceptions into the exact location of its prey.
The night vision of owls is no less incredible. Their enormous eyes occupy half the skull and their retinas are comprised of light-sensitive rod cells that gather any available light even if there is almost none. The eyes work like binoculars to search a field of vision for any tiny movement. Because an owl’s eyeballs are cylindrical (ours are round), they cannot turn in their sockets. In order to focus on sources of sound or objects at different distances, its 14 neck vertebrae (we have 7) enable an owl to rotate its head ¾ of the way around!
Hurry, Scurry Little Deer Mice
While owls are using their nighttime super powers to locate dinner in the dark, deer mice are doing their best not to become that dinner! By going underground and staying hidden in their burrows, they try to avoid detection. But it’s hard to stay concealed for long because of their voracious appetite they must travel 15 to 20 times a night to look for food! Using highly sensitive whiskers to detect temperature changes and alterations in the terrain, they navigate in darkness between their burrows and foraging sites.
Being very social, these mice communicate lots of important information to each other with ultrasonic sounds. Besides owls, many other nocturnal predators are after them, but deer mice are superior get-away artists. They excel at running, climbing, swimming and jumping (46cm into the air), and all in the dark!
Blind as a Bat?
Whoever started this myth got it very wrong. Bats have good vision and see better than we do at night. And their hearing is so good, it is like having a second kind of sight, called echolocation. While in flight, a bat emits high-pitched sound waves that bounce off objects and come back to its extremely sensitive ears. Depending on the speed, pitch and intensity of the rebound sound, the bat knows how big and how far away an object is. This is how they locate and capture their prey in midair while flying. The rate of echolocation speeds up as the bat progresses from merely flying around, to locating prey, then to zeroing in on it with a very high pulse called a feeding buzz. Moths and beetles are frequent targets.
Bat echolocation powers extend 10 to 20 metres. Beyond that range, they use their eyes to see. They fly very fast, reaching speeds of nearly 65km per hour.
Saved by the Smell!
Skunks do not see well. They do not hear well. They do not have a good sense of smell and they cannot move quickly with their small short legs. And yet, this easy warm-blooded target has almost no predators. Only starving mammals might hazard a go at a skunk. Great horned owls have more success, but they risk being blinded when they pursue a skunk. While nature seems to have deprived skunks of all the usual defenses for escape from predators, they are in fact equipped with an extremely powerful and effective weapon: scent glands.
Skunks rely exclusively on their scent glands for security. Their two grape-sized scent glands, located on each side of the anus, each hold 15 millilitres of foul-smelling yellow oily liquid that can be discharged at any threat within six metres. The spray can cause pain and temporary blindness when sprayed into eyes. Even juvenile skunks just eight days old are capable of spraying. Skunks come out at night to forage for insects and worms and they do not fear humans. Even a skunk that is backing away from you can rise into a handstand position with its hind quarters arched over its head to aim at you! If that’s not reason enough to avoid skunks, then consider that they can also carry rabies and other diseases.
Playing Possum
The opossum is another slow moving nocturnal creature that wobbles when it walks and seems defenseless against predators. However, a convincing performance worthy of Hollywood’s attention saves the day (night) for the opossum: when threatened, it curls up and pretends to be dead! At the same time, it releases a foul-smelling substance that mimics the stench of decaying flesh. For up to six hours it remains in this reeking catatonic state, baring its teeth and foaming at the mouth with its tongue hanging out. Lucky for it, predators avoid dead and decaying food.
Opossums also escape danger by hanging out in trees. Though wobbly walkers, they are excellent climbers aided by two big toes that function like opposable thumbs for grabbing and holding branches. The opossum is Canada’s only marsupial, keeping its dime-sized babies in a pouch to develop for three months. It forages from dusk to dawn looking for insects, worms, snails, slugs, nuts, birds, mice, snakes, garbage, grass, berries and plants. To cope with the chewing of this varied diet, the opossum has 50 teeth! (the most of any land mammal in North America).
Muskrat Magic
The creatures of the High Park night have all adapted to survive in the dark, but the muskrat’s strategy is a bit of a mystery. Muskrats have poor hearing, poor vision and a poor sense of smell. Yet somehow they can navigate with ease through the maze of water routes they create. It was thought they must have a good sense of direction until one researcher proved they do not! Muskrats removed from their dens and taken a very short distance away could not find their way back. Still, somehow they can find food and each other even during winter in ice-cold water under a meter of ice and snow in almost total darkness.
Love Songs Around the Pond
The male American toad can trill his musical song for up to 30 seconds at a time. It is meant to attract a female who will in fact choose her mate by assessing the quality of his song along with the attractiveness of the territory he has staked out for them. During the springtime mating season, this distinctive call amps up to a constant frantic pitch of desire. With each vocal appeal, the males puff out their throats like inflated bubble gum. These mating calls are so loud that the toad is equipped with an inner ear membrane to protect itself against deafness.
Few predators are successful in catching these creatures because toads can make themselves virtually unseeable. They avoid daylight and even moonlight. Their cryptic skin colour can change to match backgrounds. When mating, the two joined toads are motionless. When hunting, the toad also remains stock-still with only its eyes appearing above the water’s surface. (The toad couldn’t even move its head if it wanted to, but its field of vision includes the front, the sides and even partially behind.) While remaining in this immobile state, the toad’s long rapidly darting sticky tongue snatches up insects, slugs, centipedes and worms. If detected by a predator, the toad inflates itself to look much larger and excretes poison through its skin. It also urinates to make itself extra unappetizing. These defenses work against most predators except a few skunks, raccoons and snakes.
But that’s not all that makes these toads nocturnal superstars. They have incredible hearing, a good sense of smell and a good sense of touch. Most astounding of all is their vision. They appear to have night vision superior to all other animals. Even when it is too dark for humans to see anything at all, they can see quite well, including colours. Because their photoreceptors are 25 times slower than humans, their brains can form images even when a photoreceptor receives just a single photon per second. Like a camera with a very slow shutter speed, they are able to collect photons for up to four seconds at a time, meaning the images they receive may already be four seconds old. Good thing their prey is sluggish! And those amazing eyes have another function besides vision. When the toad’s tongue whips some food into its mouth, the eyeballs close, drop into the roof of its mouth and push the food down its throat.
Raccoon Talent Show
A raccoon has five-fingered hands that can untie a shoe, pull a dime out of a pocket and open latches, doorknobs and jars. It is able to climb headfirst down a tree because it can reverse the direction of its feet by 180 degrees. It can also walk away from a fall of 12 metres (4 stories)…and do all this in the dark!
A raccoon’s super power is definitely its sense of touch. Raccoons have different kinds of nerve endings in their front paws than humans have in their hands. A very high density of these special nerve endings enables raccoons to recognize things by touch alone. This sensitivity is heightened when the padding on the paws gets wet and becomes softer and more pliable. What looks like a raccoon washing its food in a pond is actually a raccoon locating and interpreting its food with highly sensitized wet fingers. Raccoons also have an acute sensitivity to vibrations that they use to help capture insects, small animals, crustaceans and fish. And that’s not all! A raccoon’s hearing is better than a dog’s, and with the help of their special Jacobson’s organ, raccoons can easily smell roots, acorns, rodents and insects that are underground.
While they are nearly colour blind and have poor long-distance vision, raccoons’ eyesight at close range is very good. The iconic black mask around their eyes that makes them all look like robbers can help reduce glare and aid night-vision. Ever wonder what that eerie nighttime luminous raccoon eye-glow is about? That’s a layer of cells beneath the retina, called tapetum lucidum, which works like a mirror to reflect any existing light back to the sensitive rod cells.
Red Fox Talkers and Stalkers
In the dark, just before sunrise, the red foxes of High Park are busy hunting and communicating in remarkable ways. With their oval pupils bringing in extra light, partnered with their binocular vision, they can catch the slightest movement in the dark. Then with their intensely sharp ears they zero in on their prey. Depending on conditions, foxes can hear the flight of crows up to five kilometres away or the small squeak of a mouse from 100 metres.
Unique among mammals, the red fox hears low frequency sounds very well and can detect small animals digging underground. When hunting a rodent, the red fox can pinpoint the sound of the prey from five metres distance, leap high above it, and while sailing through midair, steer with its tail to pounce directly on the moving target. Though they don’t even like the taste of moles, they still catch them so their kits can have live playthings. No matter how full they are, foxes continue to hunt and stash the extra food.
It’s not just their superior vision and hearing that leads foxes to their prey – a very keen sense of smell helps too. Smell also plays a big role in fox communication. By using 12 distinctly different urinating poses, the males can control the precise placement of their scent markings, indicating their home range to group members and to neighbouring foxes that come sniffing by. To signal states of fertility, foxes deposit their feces in conspicuous spots such as on top of objects, paths or food remains. Foxes also leave smelly messages with their various scent glands and their saliva. They have scent glands on their tails, faces, footpads and anuses. The contents of these glands can be discharged or rubbed on selected objects. Red foxes also use their saliva to mark certain places, especially plants.
To complete their impressive repertoire of communication, foxes are able to call to each other using 12 different sounds spanning five octaves. Even the white tips of their tails are used like signal flags to send messages to each other through the dark park.
Natural Lighting
Welcome back fireflies! Missing from the park for years, the return of these magical insects is a longed-for sign that something is right again in its High Park ecosystem. Once more we can experience the enchantment of the tiny lights flickering in the park.
The light made by fireflies is the most efficient light ever produced! 100% of the energy created by their internal chemical reactions results in light. Our own incandescent light bulb by comparison, is only 10% efficient, with 90% of its energy lost to the creation of heat.
Fireflies (actually misnamed beetles) produce the light in their abdomens. This chemically driven event, called bioluminescence, is used by firefly males to attract females. Each species of firefly has its own pattern of lighting so the males and females can find each other. If a female firefly is ready to receive the invitation of the flashing male, she returns a flash to him and then he flies to her.
This insect glows in every one of its stages from egg to larva to pupa to the adult firefly. Fireflies are most readily found in wet moist areas because their larvae feed on snails, slugs, worms and larvae. Firefly blood has a chemical in it that makes it taste revolting. After the first sampling of a firefly, that disgusted predator will never try another.
Opossum in tree. Photo: Tony Pus
