2 Hybrid Animals LEVELED BOOK • Z A Reading A–Z Level Z2 Leveled Book Word Count: 2,335 Connections Hybrid Animals Writing Write an informative article for a local paper on the science of hybrid animals. Include the benefits and challenges so readers are fully informed. Math Research five different hybrid animals not included in the text. Describe how the hybrids compare to their two parent species. Use glossary words in your description. 2 1 •Z Z•Z Written by Cheryl Reifsnyder Visit www.readinga-z.com for thousands of books and materials. www.readinga-z.com Words to Know biodiversity interbreeding Hybrid Animals chromosomes meiosis diverged offspring DNA reproduce embryos species expediting sterile fertilize susceptible genetic test tube hybrids transgenic Photo Credits: Front cover, back cover: © Tom Reed/AP Images; title page: © Todd Pusser/ NPL/Minden Pictures; page 3: © Bettmann/Corbis; page 4: © Funwayillustration/ Dreamstime.com; page 5: © Yva Momatiuk & John Eastcott/Minden Pictures; page 9: © Splash News/Corbis; page 12: © Eriklam/iStock/Thinkstock; page 13 (top): © Olga Filatova/iStock/Thinkstock; page 13 (bottom): © Flip Nicklin/Minden Pictures; page 17: © Steven Kazlowski/NPL/Minden Pictures; page 20: © FLPA/ Rex/REX USA; page 21: courtesy of Holly Steinkraus/University of Wyoming Cover: A four-day-old zedonk—a rare cross between a zebra and a donkey— stands near her mom. Title page: This wolphin is a cross between a bottlenose dolphin and a false killer whale. Even her teeth show that she is a hybrid: bottlenose dolphins have Written by Cheryl Reifsnyder eighty-eight, false killer whales have forty-four, and she has sixty-six. Page 3: This foal is a zebra-donkey hybrid. www.readinga-z.com Hybrid Animals Focus Question Level Z2 Leveled Book Correlation © Learning A–Z LEVEL Z2 Written by Cheryl Reifsnyder What are the pros and cons of interbreeding Fountas & Pinnell Y–Z different species? All rights reserved. Reading Recovery N/A www.readinga-z.com DRA 70+ What Is a Hybrid Animal? The ancient Greeks imagined creatures that were half one animal and half another—centaurs and minotaurs, griffons and manticores. These creatures may not exist, but animal hybrids do. They combine the traits of different species, and they are more common than most people realize. A hybrid is an animal that has parents of two different species. For instance, horses and donkeys are different species, but they are similar enough in appearance and behavior that they can mate with one another. If the mother is a horse, the Table of Contents baby is called a mule; if the mother is a donkey, What Is a Hybrid Animal? .................. 4 the baby is called a hinny. Human-Made Hybrids ...................... 7 When different species mate, they don’t always create a hybrid. Parent species that are too Natural Hybrids and the different may not have live offspring or, if they do, Tricky Definition of Species ................ 11 the young may be weak or unhealthy. When two When Species Overlap ..................... 16 different species do produce healthy offspring, though—as in the case of the mule and hinny— What’s the Big Deal? ...................... 18 the young usually have a combination of the Creatures by Design ....................... 20 parent species’ characteristics. The more closely the parent species are related, the more likely it Animal Hybrids: Problem or Solution? ....... 22 is that they will be able to have healthy hybrid Glossary ................................. 23 offspring. Hybrid Animals • Level Z2 3 4 Similar, but Not the Same By contrast, non-hybrid animals end up with a Female Parent Male Parent Offspring matched set of chromosomes. For instance, a horse Horse × Donkey = Mule receives one set of thirty-two chromosomes from Donkey × Horse = Hinny Mom and another set of thirty-two from Dad, making two copies of every chromosome in each Hybrid animals of the horse’s cells. A donkey receives thirty-one often have different names depending on from each parent, also ending up with two copies which species acted of every chromosome in each of its cells. as which parent. That’s because the In a hybrid animal, though, Mom’s characteristics of the chromosomes are different from Dad’s. A mule hybrid animal are doesn’t have two copies of anything—just a often determined by jumble of sixty-three chromosomes, none of which which species was have matches. the mother. In the case of donkey-horse The mule’s chromosomes don’t need to hybrids, mules are form matched pairs for normal cell division: the generally larger and hardier than hinnies. mule chromosomes simply form copies of themselves and sort one copy into each of the new cells. However, when the mule tries to make reproductive cells, those unmatched chromosomes Like many hybrid animals, mules and hinnies cause problems. are sterile—unable to make sperm or eggs to produce offspring. This situation stems from the Unlike most cells, sperm and egg cells have fact that different species of animals often have only one copy of each chromosome. Getting different numbers of chromosomes. Mules and to that one-copy state requires a process called hinnies receive nonmatching genetic information meiosis, which requires each chromosome to line from their horse and donkey parents: thirty-two up with its match so one member of each pair can horse chromosomes from one parent and thirty- be sorted into separate cells. one donkey chromosomes from the other. Hybrid Animals • Level Z2 5 6 Since the horse and donkey chromosomes and produce meat lower in fat than standard beef. don’t look very much like one another, they can’t However, buffalo are difficult to handle and can form nice pairs. The dividing cell has a hard time sometimes be dangerous. sorting the right chromosomes into the right Beefalo are as easy to handle as ordinary cattle places; some offspring cells receive too many but are much hardier and easier to care for. They chromosomes and others receive too few. These have an efficient digestive system, which allows cells rarely survive. them to eat leaves and bushes as well as grass. Human-Made Hybrids Unlike cattle, they are able to withstand both Sometimes people breed hybrids intentionally, hot and cold temperature extremes. Like buffalo, hoping to produce a hybrid that has the best their meat is low in fat, with more protein than qualities of both parent animals. Mules have been standard beef. Unlike zebroids or mules, beefalo deliberately bred since ancient times because they are able to reproduce, as long as breeders are are hardier and more sure-footed than horses. mindful of their math. It turns out that the ratio Mules are also easier to care for than horses—less of three-eighths bison to five-eighths cow is ideal. likely to overeat, less susceptible to heat, and less As long as the proportion of bison is kept at or prone to leg injuries. below the three-eighths level, there are few—if any—reproductive problems. Zebra hybrids, sometimes called zebroids, are a more recent type of hybrid. Zebras are A liger, which is a hybrid of a male lion and wild animals that are difficult to train for riding a female tiger, looks like a supersized lion with or carrying packs, but they aren’t susceptible faded tiger stripes. Ligers grow about twice as to the same diseases as domesticated equines. large as either parent species, with Hercules, the Zebroids inherit a gentler personality from their world’s biggest male liger, weighing in at nearly domesticated parent as well as resistance to 1,200 pounds (544 kg)! They are usually tawny disease from their wild parent. colored, like lions, but with pale bellies, like tigers. A similar hybrid, the tigon, is created by breeding Beefalo, another recent hybrid, were created the opposite genders of parents—a female lion to combine the traits of buffalo (bison) and and a male tiger. domesticated cattle. Buffalo are hardier than cattle Hybrid Animals • Level Z2 7 8 Hybrid Parent Species (Female, Male) Characteristics • Size and strength of a horse Hercules, the Mule Horse × Donkey • Endurance, hardiness, and sure- world’s biggest footedness of a donkey cat, poses with his little brother • Like a mule, but smaller and Hinny Donkey × Horse Aries. Both less hardy are ligers. • Cattle-like temperament • Buffalo-like in that they are Beefalo* Bison × Bovine hardier, have a more efficient digestive system, and yield lower-fat meat * Ideal ratio: 3/8 bison and 5/8 cow Zedonk Zebra × Donkey Ligers never occur naturally since lions and • Disease resistance of a zebra tigers live in different habitats. However, these • Temperament midway between a zebra’s and a domestic animal’s strange mixes can draw a crowd, and although Zorse Zebra × Horse • Striking appearance that is accredited zoos avoid interbreeding the big cats, a combination of the parent both independent breeders and exotic animal species’ look Zony Zebra × Pony preserves have tried their hand at making money from them. Breeders have created other big cat • Tawny coat like a lion, partial hybrids as well: leopons (leopard × lion), jaguleps Liger Tiger × Lion stripes, mane on some males (jaguar × leopard), and lijaguleps (lion × jagulep). • Larger than either parent The males of these hybrids are usually sterile, but • Tiger-sized, appearance midway Tigon Lion Tiger the females are usually able to bear offspring. × between a tiger and lion Until recently, people could only obtain • Larger than domestic house cat, Savannah Domestic African × long legs, serval-like fur pattern hybrids of similar species that might be willing Cat house cat serval • More dog-like in their behavior to mate with each other. Other species, while somewhat similar, were unwilling. For instance, • Strong, but smaller than a camel even when given the opportunity, camels and Cama Llama × Camel • Better temper and easier to handle than a camel llamas would rarely mate.