Curious Creatures — May - June 2002

Step right up to nature's sideshow wonders.

illustration of curious creatures

By Jennifer Amie and Jennifer Menken. Illustrations by Jennifer Menken.

The fox snake (Elaphe vulpina) did not earn its name by being as sly as a fox. When startled, the fox snake gives off a strong, musky smell, resembling the odor of a fox.

Like a rattlesnake, the fox snake rapidly shakes its tail when spooked. Though it has no rattle, it sounds like a rattlesnake as its tail rustles dry leaves or grass. Because the fox snake is large and has a blotchy brown and tan pattern much like a rattlesnake, its display is convincing, and people often mistake these pretenders for actual rattlesnakes. Mistaken identity sometimes leads to the demise of this harmless southern Minnesota snake.

If wild animals won Academy Awards, the western hognose snake (Heterodon nasicus) ought to be nominated for best actor. When menaced by hawks, crows, foxes, raccoons, or people, the hognose spreads out the ribs behind its head, forming a "hood" like a poisonous cobra. Its head appears to double in size. Then the hognose hisses loudly and strikes repeatedly (with its mouth closed). If that doesn’t scare off the predator, the snake convulses violently, poops on itself, rolls onto its back, and plays dead. If the predator flips it right side up, the hognose turns over on its back again. After all, everybody knows that a dead snake lies belly up. From this upside-down position, the dead-looking hognose occasionally lifts its head and peeks to see if the danger has passed.

The gray treefrog (Hyla versicolor), like some other species of Minnesota frogs, freezes. It spends the winter nestled in dead leaves, rocks, or logs on the forest floor. Its body can survive outdoor temperatures as low as 19 F.

The water in the spaces between the frog’s organs and muscles freezes. In fact, 65 percent of the treefrog’s total body water can be frozen. To protect its organs and muscles, the treefrog has its own sort of antifreeze. When cold temperatures arrive, the frog’s liver turns glycogen into glycerol, which protects the frog’s cells from damage.

After a long, cold winter’s nap, the gray treefrog thaws, wakes up, and hops away.

The beaver (Castor canadensis) has several unusual traits that help it swim and work underwater. For example, the beaver has flaps of skin on both sides of its mouth. When the beaver gnaws or carries wood underwater, the flaps close behind its teeth, so it won’t gulp pond water. The beaver can also pucker up, closing its lips together in front of its teeth.

The beaver’s ear and nose valves shut out water. Like goggles, clear membranes cover and protect its eyes.

Because it can tolerate an unusually high level of carbon dioxide in its blood, the beaver can hold its breath for a long time. Most dives last just a few minutes, but the record is about 15 minutes.

With all of these traits, as well as webbed hind feet and a rudderlike tail, the beaver is well-equipped for life in its watery habitat.

Contrary to popular belief, the ruby-throated hummingbird (Archilochus colubris) does not hitch a ride on the back of a goose to migrate to and from its wintering grounds in Central America. In fact, the tiny bird, which weighs no more than a penny, flies solo nonstop across the Gulf of Mexico, about 600 miles. It cannot stop to rest because it cannot land on water. The journey across the gulf takes 18 to 24 hours.

The hummingbird builds the world’s smallest bird nest, using spider webs, lichens, moss, and spit. About the size of half a walnut shell, the nest holds two pea-sized eggs.

The smallest mammal in North America lives in northern Minnesota. The pygmy shrew (Sorex hoyi) weighs only 1Ú10 ounce (about as much as a penny) and measures just over 3 inches long, including its tail.

This little ball of fur is one of the world’s biggest eaters. Every day the pygmy shrew eats its own body weight in worms, insects, and even mice. To keep its speedy system running, it needs to eat every few hours. Without food, the pygmy shrew would starve in less than a day.

The pygmy shrew’s larger and more common cousin, the short-tailed shrew (Blarina brevicauda) is one of the few venomous mammals in the world. When this shrew bites, its poisonous saliva can kill a mouse its own size or bigger.

If a human were to be bitten by a shrew, the spot would swell up like an insect bite. The chance of anyone getting bitten by a shrew is very small.

The male fathead minnow (Pimephales promelas) woos its mate to its nest by "singing." The minnow probably produces this melodic clicking sound by grinding his back teeth against the base of his skull.

When choosing a mate, the female fish considers the male minnow’s looks, as well as his singing talent. During the spawning season, the male’s head swells, thus earning the name "fathead." The male also develops hornlike bumps, called tubercles, on its snout and back. Like your fingernails, tubercles are made of keratin.

The female deposits her sticky eggs on the underside of a board, branch, or rock in 3 to 12 inches of water. Then, the male fertilizes them and guards the nest. He cleans, gently fans, and endlessly strokes the eggs with his tubercles.

Fathead minnows are commonly used as fishing bait.

The paddlefish (Polyodon spathula) is a monster-size fish with a long, paddle-shaped nose. Its nose and the sides of its head have electro-receptors that can sense nearby living organisms. Because it lives in dark, murky water where it is hard to see, the paddlefish counts on its electro-receptors to find food—mainly colonies of tiny animals, known as zooplankton. Paddlefish strain zooplankton through their gill rakers.

Paddlefish may grow to be 65 pounds or more. In Minnesota, paddlefish are found in the Mississippi and lower St. Croix rivers.

Some animals really do have strange eating habits. The great horned owl (Bubo virginianus) snacks on skunk. Of course, it helps that the great horned owl, like other owls, has almost no sense of smell.

Both skunks and owls are nocturnal—they hunt for food during the night. The great horned owl has extraordinary hearing and night vision. Its feathers have very soft edges that allow the owl to fly silently and sneak up on a skunk.

If skunks aren’t around, the owl will eat opossums, weasels, turkeys, bats, rabbits, other birds, bullheads, crayfish, beetles, snakes, or almost anything else it can catch.

When workers tore down a building in Minneapolis long ago, they discovered an unusual mummy of a pigeon (Columba livia). The bird apparently had become trapped inside the walls of the building and, over time, dried out. Insects came along and ate the pigeon’s internal organs and the soft parts of its feathers. They left behind the skeleton and other dry, hard parts. The central ribs of the pigeon’s feathers remain attached to the corpse, giving the mummy its bizarre, spiky appearance.

A complete copy of the article can be found in the May - June 2002 issue of Minnesota Conservation Volunteer, available at Minnesota public libraries.

Jennifer Amie is publications coordinator and Jennifer Menken is museum naturalist, both at the Bell Museum of Natural History,University of Minnesota, Twin Cities.