GRADE LEVELS: 5-8

TIME ALLOTMENT: One or two 45-minute class periods

OVERVIEW:

In this lesson, students will learn about the various attributes of different predators on the African grasslands which make them effective hunters, and about the attributes their prey have developed to help them survive the predators’ attacks. The development of both sets of attributes will be presented as part of natural selection—a process which takes varied forms (and produces varied results) in the earth’s different ecosystems.

In the Introductory Activity, students will use an online interactive to familiarize themselves with the physical attributes of the cheetah which make it such an effective predator. In the Learning Activities, students explore the cheetah’s use of these attributes in pursuit of its equally well-adapted prey—the gazelle—through video from the “Hunters and Herds” episode of the PBS series NATURE, which also discusses the similar contest between lions and wildebeests. The Culminating Activity challenges students to research, compare, and contrast predator/prey relationships in earth’s different ecosystems, and present their findings to the class.

This lesson is intended for use during study on natural selection and adaptations, or a unit on the food chain/web.

SUBJECT MATTER: Science, Biology

LEARNING OBJECTIVES:

Students will be able to:

• Identify the attributes of different predators which contribute to their effectiveness as predators
• Identify the attributes of different prey animals which contribute to their ability to elude predators
• Discuss how the attributes of both predator and prey animals have developed in a process of natural selection
• Compare and contrast predator/prey relationships from different ecosystems around the world.

STANDARDS:

National Science Education Standards

Life Science

Content Standard C

As a result of their activities in grades 5-8, all students should develop understanding of:

1. Structure and function in living systems
2. Reproduction and heredity
3. Regulation and behavior
4. Populations and ecosystems
5. Diversity and adaptations of organisms

MEDIA COMPONENTS:

Video: NATURE: “Moments of Impact– Hunters & Herds”

Clip #1 “Cheetah vs. Gazelle”

An animation-enhanced comparison of the strengths and weaknesses of this predator and prey pair.

Clip #2 “Lion vs. Wildebeest”

An animation-enhanced comparison of the strengths and weaknesses of this predator and prey pair.

Websites:

“Toki’s Survival Challenge”

An interactive in which a cheetah hunts its prey on the African savannah. From the PBS NATURE web site.

“Anatomy of a Cheetah”

A simple interactive highlighting the primary physical attributes of the cheetah as a predator.

MATERIALS:

For the class:

• 1 computer w/ internet connection and projector

For each group of 3-5 students:

• 1 computer w/ internet connection

PREP FOR TEACHERS:

Prior to teaching this lesson, you will need to:

Preview all of the video segments and websites used in the lesson.

Download the video segments used in the lesson to your classroom computer, or prepare to watch them using your classroom’s internet connection.

Bookmark the website used in the lesson on each computer in your classroom. Using a social bookmarking tool such as del.icio.us or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Next: Proceed to Activities.

Excerpts from the NATURE episode, “Moments of Impact: Hunters and Herds”

Cheetah vs. Gazelle
(View full post to see video)

Lion vs. Wildebeest
(View full post to see video)

Downloadable QuickTime versions of the video segments:
(Note: To download a video, right click on the video title and click “Save Link As…’ or “Save Target As…”. On a Mac, press the CTRL key and simultaneously click the mouse, then save the link.)

Video Clips

1.“Cheetah vs. Gazelle”

2.“Lion vs. Wildebeest”

Spanish sailors called them the “whale killers.” The Haida of British Columbia knew them as the “killing demons.” To the Japanese, they were “fish tigers.”

Whatever the name, seafarers have long been awed by the hunting prowess of the large black-and-white dolphins known as orcas, or killer whales. Among their admirers are the whalers who sailed Australia’s Twofold Bay from nearly a century ago up to the 1970s. As NATURE’s Killers in Eden shows, these human whale hunters say they formed a partnership with the orcas, which helped them herd and hunt whales.

Those stories are difficult to substantiate. But researchers say it is certainly true that orcas exhibit remarkably creative, complex, and often cooperative hunting strategies. The highly social animals, which typically travel in groups called “pods,” are known to feed on everything from fish and seabirds to seals and giant blue whales.

Orca pods living in particular waters tend to specialize in certain species. In the North Atlantic, for instance, some orcas follow schools of herring. Working together, they’ll surround a school and herd it into a tight ball — sometimes by releasing a curtain of bubbles. Then they’ll take turns slashing through the school, stunning or killing fish with a slap of their powerful tails. Finally, they eat the dazed or deceased fish one by one.

Other pods specialize in picking off seals or sea lions. Along the California coast, for instance, they’ve been seen tossing unfortunate seals high into the air, probably in an attempt to stun them. Along the coast of Argentina, mother orcas teach their young an equally impressive hunting tactic — the killer whales literally fling themselves up on beaches in pursuit of young seals, then flop back into the sea with their meal. Apparently the taste of seal is worth the risk of getting stranded.

Orcas exhibit remarkably creative, complex, and often cooperative hunting strategies.

Orcas exhibit remarkably creative, complex, and often cooperative hunting strategies. Some orcas even use bait. They’ve learned that they can lure in a flock of seagulls by regurgitating fish and letting the scraps float to the surface. When the gulls land to eat the fish, they become the orcas’ feast instead.

In polar seas, orcas have discovered another trick. When penguins or seals take refuge on a piece of floating sea ice, killer whales rock the fragile raft, trying to knock off its occupants. Or, better yet, they use their bodies and tails to stir up waves that wash their prey off the ice and into the water, where another orca waits to snap them up.

Perhaps the most spectacular — but least understood — orca feeding behavior involves great whales. The orcas, which can reach 28 feet in length, sometimes take on whales many times their size. Usually, however, they go after young whales. First they’ll try to separate the youngster from its mother by chasing it for hours or days. Then they’ll surround the young whale and try to block it from reaching the surface to breathe.

Despite their fierce reputation, orcas have little taste for one seagoing animal: humans. Researchers say there are no documented cases of a wild orca intentionally hunting a human, although there have been attacks in sea parks. And there have been several cases where an orca may have mistaken a surfer or swimmer for some other animal.

The whalers of Eden, however, say orcas were not a threat. Instead, they acted as partners, steering their boats to whales out in the bay and, helping sailors who had fallen overboard back to safety. Far from killers, the whalers of Eden say their orcas were saviors.

The cheetah is the world’s fastest land animal.

Cheetahs must learn to stalk their prey. When it comes to cheetahs, speed kills. Indeed, cheetahs rely on their remarkable acceleration abilities to overtake fast moving prey, such as small antelope. But speed alone isn’t enough to ensure a successful hunt, as NATURE’s Cheetahs in a Hot Spot shows. Baby cheetahs must also learn to stalk their prey and perfect a carefully choreographed killing sequence known as “chase-trip-bite.”

Before the chase begins, however, cheetahs must creep within just a few hundred feet of their target, because their bursts of speed don’t last long. Then, quickly accelerating to nearly 60 miles per hour, the cheetah overtakes the prey in a surprise rush. Once close, it lashes out with a front foot, and a specially designed rear claw catches the hind leg of the victim, tripping it.

A cub has to master the “chase-trip-bite” sequence. To finish the kill, the cheetah must then grab the winded animal’s throat in its jaws and clamp the windpipe shut, suffocating the prey. Once it is dead, the cheetahs will start snacking on the animal’s rear flanks, where the most nutritious meat is found.

But some cubs can be slow learners, notes Person. “Young cheetahs may start their rush too far away, or get the chase and the trip right, but become confused about where to bite,” he notes. “Even though it is an instinctive behavior, they have to perfect it.” Cheetahs in a Hot Spot highlights one such trial run, in which a cheetah pack successfully downs an antelope, but then has trouble finishing off the crippled animal. Eventually, however, they learn to earn their meal. “If they don’t get it right,” notes Person, “they’ll die. Nature has a way of sifting out the less capable cubs.”

A cub has to master the “chase-trip-bite” sequence.

Even successful hunters often face challenges once the hunt is over. Lions, hyenas, and other animals often try to steal the cheetah’s freshly killed meal. The cheetahs are sometimes so exhausted from the chase, they can’t prevent a thief from walking off with their kill.