Steve Jenkins & Robin Page
Page 1
How to Clean a Hippopotamus
A Look at Unusual Animal Partnerships
Steve Jenkins and Robin Page
* * *
HOW TO CLEAN A
HIPPOPOTAMUS
A LOOK AT UNUSUAL ANIMAL PARTNERSHIPS
Steve Jenkins & Robin Page
Houghton Mifflin Books for Children • Houghton Mifflin Harcourt
Boston New York 2010
Sometimes animals form surprising
partnerships …
Why does a giraffe let an oxpecker climb into its ear?
Why does a crab wave an anemone like a pom-pom?
Why do a coyote and a badger team up?
Why does a plover stroll into a crocodile’s mouth?
And how does a turtle keep a hippopotamus clean?
These creatures—and many others—have formed relationships in which each animal helps the other. This is called symbiosis. This book explores some of these unusual partnerships …
LOOK, LISTEN, AND SNIFF.
On the African savannah, grazing animals must lower their heads to eat, which can make it easier for a predator to sneak up on them.
Three different animals have found that feeding together makes them safer: each detects danger in a different way.
The zebra has excellent hearing. It stays alert for the sound of danger.
The wildebeest has an acute sense of smell. If the wind is blowing the right way, it can sniff out a nearby predator.
The ostrich, the tallest of the three, has sharp vision. It frequently lifts its head and looks around.
GOING MY WAY?
The cattle egret is a long-legged bird of the African grasslands. Grasshoppers are one of its favorite foods.
This egret hitches a ride on a
waterbuck, a large antelope.
As the waterbuck grazes, its hooves stir up grasshoppers hidden in the grass.
The insects fly up and the egret swoops down and nabs them.
The egret helps the waterbuck by warning of danger with a loud call.
LOOK OUT! That lion is getting too close for comfort.
The giraffe can keep most large predators at bay with sharp hooves and a powerful kick …
LOWER, AND A LITTLE TO THE LEFT.
… but like many wild animals, it is tormented by tiny ticks and other skin parasites.
The oxpecker, also known as a tickbird, eats ticks and insects.
The oxpecker searches for ticks and insects, pulling them off with its beak.
The oxpecker will warn its host of approaching predators. If its giraffe has fallen asleep, the bird wakes it with loud shrieks and flapping wings.
The giraffe lets the bird pick off pesky
parasites wherever it can find them.
HAVE BEAK, WILL TRAVEL.
Giraffes aren’t the only large animals that form partnerships with the oxpecker.
Here, an oxpecker de-bugs a rhino.
Another helps out a deer.
And a third inspects an African buffalo.
These oxpeckers take a song break from zebra cleaning.
All of these large animals benefit by having fewer parasites, while the birds get to feast on their favorite food.
WIDER, PLEASE.
The Egyptian plover is sometimes called the toothpick bird.
The plover feeds on scraps of meat that get stuck in the teeth of the Nile crocodile.
The crocodile will devour any animal it can catch, but it won’t eat a plover. In return for a tooth cleaning, it lets the little bird come and go freely.
DINNER IS SERVED.
The ocean sunfish, or mola mola, is one of the largest fish in the sea. Its skin, like that of many ocean animals, is often infested with worms and other parasites.
As a hungry seagull soars above the waves, it notices a large fin waggling back and forth.
This is a signal. The fin belongs to an enormous fish, and the seagull moves closer.
The sunfish rises to the surface and rolls onto its side. The seagull swoops in …
… and uses its beak to pry parasites from the fish’s skin.
People sometimes mistake the sunfish’s fin for that of a large shark, but it’s easy to tell the difference. A shark’s fin cuts straight through the water, but the peculiar shape of the sunfish’s body makes its fin wobble.
CLIMB ABOARD, MATE.
The hippopotamus spends much of its time in the water …
… where its skin becomes covered with algae and water plants.
An African helmeted turtle can help.
As in many other cleaning relationships, the hippo holds still while the turtle does its work, nibbling away unwanted greenery.
The hippo also lets the cold-blooded turtle use its back as a platform for basking in the sun.
MORE THAN MEETS THE EYE.
The sea anemone and the clownfish, with its immunity to the anemone’s poisonous tentacles, are one of the best-known examples of animal symbiosis. But this relationship is more complex than it might appear.
At first, the clownfish isn’t immune to the anemone’s toxin. It must acquire its resistance by brushing lightly against the stinging tentacles, gradually touching them more and more.
The clownfish is immune only to its own anemone. If it swims into another anemone—even one of the same kind—it will be killed.
The clownfish hides from predators among the anemone’s stinging tentacles. It helps the anemone find food by luring other fish to their death in the anemone’s tentacles.
If the clownfish leaves its anemone for more than 45 minutes, it will no longer be safe. It will have to start over, once again exposing itself gradually to its anemone’s stings.
ARMED AND READY.
The shell of the tiny boxer crab is about the size of your thumbnail.
Even a small anemone has thousands of deadly stinging cells on its tentacles …
… but the little crab plucks two anemones from the sea floor.
A hungry grouper swims closer …
… thinking that a boxer crab will make a nice snack.
As the big fish moves in for the kill,
the crab displays its living weapons like a boxer waving his gloves.
Later, when the crab has its own meal, the anemone is rewarded with stray scraps of food.
The grouper decides to look for easier prey somewhere else.
HOLD ON!
Other crabs also carry living protection and camouflage on their backs. Their passengers get bits of food that drift up as the crabs eat.
The hermit crab lives in a shell abandoned by another animal. It tickles an anemone with its claws, and the anemone climbs onto the crab’s shell. Its stinging tentacles protect the crab.
The sea sponge isn’t poisonous, so it can’t defend the sponge crab that gives it a ride. But it’s hard for a predator to spot a crab with a colorful sponge growing on its back.
With its pincers, the crab keeps the sea sponge trimmed to just the right size.
The decorator crab adorns its shell with anemones, sponges, and bits of shell and seaweed. It looks like part of the sea floor.
Unlike other animals that live on a crab’s shell, the upside-down jellyfish is not permanently attached. The jellyfish’s stinging tentacles provide protection in return for crab meal leftovers.
I’LL WATCH THE BACK DOOR …
Prairie dogs live in underground colonies. These plump rodents …
… are one of the coyote’s favorite foods.
The badger, an expert burrower, also hunts prairie dogs.
In some places, coyotes and badgers ha
ve learned that they can catch more prairie dogs if they hunt together.
The coyote has keen eyesight. It spots a prairie dog colony.
If the coyote attacks, however, a sentry sounds the alarm …
… and the prairie dogs duck into their underground tunnels.
So instead of rushing in, the coyote sets off to find a badger.
The badger usually hunts alone, but it knows that a coyote can lead it to food. It follows the coyote back to the prairie dog colony.
The prairie dogs spot trouble coming. It’s time to take cover!
The coyote sniffs out a back entrance to the burrow and waits.
Meanwhile, the badger rips into the burrow entrance with powerful claws.
The colony panics and the coyote pounces, nabbing one prairie dog as it bolts from a rear exit.
Another darts back into the burrow …
… straight into the jaws of the waiting badger.
NOT THE BEST OF FRIENDS.
A flock of ravens circles overhead. They are following a wolf pack that is on the move.
The ravens look on from above as the wolves, working together, attack an elk.
Ravens are thieves. As soon as the kill is made, they crowd in to steal what they can.
The wolves try to drive the aggressive birds away.
But sometimes the ravens help the wolves. If they find a carcass that’s too tough for them to eat, they caw loudly and more birds arrive on the scene. If wolves hear the call, they come too.
The wolves tear open the carcass, getting a meal for themselves and leaving the leftovers for the ravens.
FOLLOW ME!
A honeyguide spies a bee in flight …
… and trails it back to its beehive.
The honeyguide isn’t strong enough to break in to the bees’ nest, so …
… it finds a ratel, or honey badger, and flutters around it.
The ratel knows that this means honey. It follows the honeyguide to the bee’s nest.
The honeyguide waits nearby while the ratel tears open the nest and gorges on honey. Its tough skin and thick fur protect it against bee stings.
Once the ratel has had its fill, the honeyguide dines on scattered bits of wax honeycomb and juicy bee larvae.
THAT TICKLES!
The sparse hair of the warthog does a poor job of protecting its skin from insect pests.
Insects filled with warthog blood are a favorite food of the mongoose.
An itchy warthog spots a group of mongoose. It lies down …
… signaling the small, catlike mammals. They come running …
… and clamber all over the warthog, which lies quietly while its skin is picked clean.
SEASIDE SERVICE.
The marine iguana is the world’s only oceangoing lizard. It lives on the Galapagos Islands …
… where it spends much of its time in the sea, feeding on algae.
The water here is cold, and the iguana must periodically warm its body by lying in the sun.
As it basks, a Sally Lightfoot crab takes notice.
Soon this agile land crab is scrambling over the iguana’s body.
It eats ticks and feeds on bits of the lizard’s dead skin.
A STREAMLINED HITCHHIKER.
The remora attaches itself to a tiger shark with a special suckerlike fin on the top of its head. The smaller fish gets a free ride and feeds on scraps from the shark’s meals.
The remora helps its host by vacuuming algae and parasites from the shark’s skin.
CLEANING WHILE YOU WAIT …
The cleaner wrasse gets its food as it removes parasites from all sorts of sea creatures. These fish gather in a particular spot—a cleaning station—where they service a constant stream of visitors.
A moray eel, which would normally make a meal of a small fish, is on its best behavior at a cleaning station. It holds still while the wrasse does its work.
A parrotfish …
… a stingray …
… and a potato cod all visit the wrasse cleaning station.
… AND A LITTLE COMPETITION.
Other fish also provide cleaning services. A school of tang have dinner as they give this green sea turtle a thorough shell cleaning.
ROOMS FOR RENT.
The African social weaver is a champion nest builder.
Social weaver nests are among the largest animal-made structures in the world. As many as 400 birds may live in a single nest. Each family has its own entrance and nesting chamber.
An African pygmy falcon moves into the weaver’s nest. In many cases, the falcon won’t harm the smaller birds. It gets a ready-made home …
… and helps the weavers by killing snakes and reptiles that prey on the small birds or their eggs.
TRUCE?
Black tree ants build their nest on a branch high above the ground.
The black ants guard their basketball-sized home fiercely, attacking and stinging any animal that comes too close.
The rufous woodpecker normally tries to eat the ants, often getting stung in the attempt.
But in the spring, when it’s time for the female woodpecker to lay her eggs, the situation changes.
The bird makes a hole in the nest—a chamber in which she lays her eggs. The ants don’t attack her, her eggs, or the newly hatched chicks.
The woodpecker doesn’t eat the ants, and until the eggs hatch and the baby birds leave the nest, she will help defend it against predators.
Once the baby birds leave the ant nest, however, the ants and the rufous woodpecker become enemies once again.
DAY FOR NIGHT.
The tuatara is an ancient species of reptile that lives in New Zealand.
The tuatara makes its home in the nesting burrows of the petrel, a sea bird.
The petrel is active during the day and sleeps in its burrow at night.
The tuatara is nocturnal. It sleeps during the day and hunts at night.
Their different schedules allow these two animals to share the nest without too much conflict. The petrel built the nest—how does the tuatara help the bird?
It defends the nest, attacking any animal that threatens the bird or its eggs.
The droppings of the petrel attract insects, spiders, and worms. The tuatara eats these, keeping the nest pest-free.
A GOOD NEIGHBOR.
The goby is a small fish that makes its home in cracks, crevices, and holes in the sea floor. It can’t dig its own burrow, so it often shares a home with some other creature.
When a blind shrimp shares its burrow with a goby …
… the shrimp uses its antennae to stay in contact, and the fish leads the blind shrimp to food.
In case of danger, the goby darts into the burrow. The shrimp follows.
Another goby lives with a pea crab in a sea floor tunnel excavated by a worm.
If the goby finds a piece of food too big for it to eat, it brings it back to the crab, which tears it apart with its claws.
Crabs are messy eaters, and the goby gets some of the scraps.
Still another goby lives near a giant clam.
If the fish spots danger, it darts into the clam’s shell. The clam snaps its shell shut, protecting itself and the goby.
After a while, the clam opens its shell a little. If the coast is clear, the goby swims out.
TENDING THE FLOCK.
Thousands of meat ants live together in underground nests.
During the day the ants leave their nest …
… to tend flocks of baby leafhoppers, or nymphs.
As the nymphs feed on plant juices, the ants protect the baby leafhoppers from predators.
The ants stroke the nymphs’ abdomens with their antennae.
In response, the nymphs excrete a drop of sweet liquid called honeydew, which is the ants’ main source of food.
YOU CAN FOOL ALL OF THE ANTS SOME OF THE TIME …
A large, brilliantly colored blue butterfly lays its eggs on a plant growing in a meadow.
>
The egg hatches into a caterpillar, which begins to eat the leaves of the plant.
Then the caterpillar does a strange thing. It lets go of the plant and drops to the ground.
The meadow floor is a dangerous place for a caterpillar. There are ants and other predatory insects everywhere.
Sure enough, a red ant soon finds the caterpillar and drags it back to its nest.
But the caterpillar has a trick: it produces a chemical that smells like an ant larva. So instead of eating the caterpillar, the ants clean and protect it.
Soon, the caterpillar spins a cocoon and becomes a chrysalis. It continues to fool the ants by making a clicking sound like one the ants themselves make.
The ants believe that they are caring for one of their own.
In return, the caterpillar produces a sweet liquid, which the ants drink. The caterpillar eats some of the ant larvae, but the ants don’t seem to notice.
At last the blue butterfly emerges from its cocoon. It can no longer fool the ants, and it must leave the nest quickly or be killed by its former caretakers.
WHO’S IN CHARGE HERE?
Dogs and humans have lived together for thousands of years. Their relationship is probably the most commonly observed symbiosis in the animal world.
In return for food and shelter, the first domestic dogs —descendants of the wolf—helped protect human settlements and livestock.
Today, dogs help humans in many ways:
as workers …
… hunters …
… herders …
… and guides.
In return, humans feed dogs, provide a home for them, keep them healthy …
… and give them the attention they seem to crave.
Today the most important role for dogs is that of companion. Dogs keep us company and cheer us up when we’re sad. They are loyal and affectionate.
We’ve looked at just a few of the mutualistic symbiotic relationships in the animal world. There are thousands—perhaps millions—of others, many of them still waiting to be discovered.