Steve Jenkins - Sisters and Brothers: Sibling Relationships in the Animal World

sibling relationships in the animal world

sisters & brothers

steve jenkins & robin page
houghton mifflin company boston 2008

Playing together, working together, arguing, fightingsometimes animal brothers and sisters act a lot like human siblings. Other creatures have more unusual relationships. They may be identical quadruplets, or have only sisters. Some have hundreds, thousands, or even millions of brothers and sisters. There are animal brothers that fight to the death, and others that are companions for life. In this book you can read about some of the ways animal siblings get alongor not. At the back of the book you can find out more about each creature's size, what it eats, and where it lives.

One at a time

Bringing up baby.

Like humans, African elephants are usually born singly. Elephants weigh 200 pounds (440 kilograms) or more at birth, but even a youngster this size isn't safe from lions and other predators. If a baby elephant wanders away from its herd, an older sister will often act as a babysitter and guide it back to safety. A typical elephant herd includes twelve to fifteen family members led by an older female. Young elephants are well cared for until they are about twelve years old. At this age, males leave the group to live on their own. Females, however, stay with the herd and help take care of their younger siblings, bathing them, feeding them, and keeping them safe.

Let's hold on!

Two tiny bats hold on to their mother's fur, one under each of her wings. They hang on while she hunts and stay safely in place as she folds down her long ears to sleep. Gould's long-eared bats are almost always born as twins. They stay together, clinging to their mother, until they are about four months old. When these small mammals begin to fly on their own, they will hunt and navigate using echolocationmaking a rapid series of high-pitched calls and listening for the echoes. In this way, bats can catch insects and avoid obstacles even when flying in complete darkness.

Twins

Quadruplets

Exactly alike.

Nine-banded armadillos are always born as identical quadrupletsfour brothers or four sisters. They are clones, perfect copies of one another, so they are exactly alike down to their toenails. Armadillos are born with their eyes open and can walk when they are just a few hours old. The quads stay with their mother for several months before setting off on their own. When full grown, this armored mammal is about the size of a small dog. If it is threatened, an armadillo can run, jump, or swim surprisingly quickly. If all else fails, it rolls itself up into an armored ball.

Girls rule!

New Mexico whiptail lizards have only sisters. There are no brothers, because there are no male whiptails. All the sisters in a whiptail community are identical. They are also identical to their mother, their grandmother, and all their female ancestors. Female whiptails don't need to find a mate to produce offspring. Plants often reproduce this way, but animals rarely do. Reproduction without a male does have some advantages, since whiptails don't have to spend any time or energy finding a mate. However, since all the lizards in one of these family groups are exactly the same, a disease or change in habitat that is fatal to one animal could wipe out the entire community.

Sisters

A large family

Two naked mole rats, hairless and nearly blind, meet in an underground tunnel. They stop and sniff each other. Then one mole rat lies flat on the tunnel floor while the other walks right over its back. These two rodents are siblings. There may be hundreds of animals in this colony, and almost all of them are brothers and sisters. They are the offspring of a single female, the queen. She is the only member of the colony that can have babies. Animal societies of this sort are common in the insect world but are very unusual among mammals. Mole rats use their large front teeth to dig a complex tunnel system, their colony's home. Within each colony there is a strict system of social status, or rank, based on a member's age and occupation. When two mole rats meet, the lower status brother or sister has to lie flat on the floor to let its sibling pass by.

Hundreds of siblings.

Mommy's busy right now...

Millions of termite brothers and sisters may live together in a single mound, or nest. These mounds, the largest non-man-made structures in the world, are sometimes as tall as a four-story building. A single female termite, the queen, may produce as many as 30,000 eggs a day for her colony. Every termite sibling has a job to do. Workers repair the nest, collect food, and take care of the queen, who is so heavy that she can't move on her own. Soldiers are larger and use their huge jaws to defend the nest against attack. Termites look a bit like ants but are closely related to cockroaches.

A very large family

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