Real Science

Tuesday, 10 July 2007

Bone-crunching wolves

University of California, Los Angeles: 21-Jun-2007 12:00 Eastern US Time

The icy expanses of Alaska were once the home of large, bone-crunching wolves. This was a unique type of wolf that died out, along with many other big animals, at the end of the Pleistocene.

These extinct Alaskan wolves had robust bodies, strong jaws and massive canine teeth. They regularly killed prey larger than themselves and ate their bones, according to research in today's online edition of Current Biology.

These results are surprising, says Blaire Van Valkenburgh of the University of California, Los Angeles. "The unique attributes of Alaskan Pleistocene wolves had not been previously recognised. They show that wolves suffered an extinction at the end of the Pleistocene."

This new research shows that if wolves had not survived in the Old World, there might not be any wolves in North America today.

"But the living gray wolf differs dramatically from that which roamed Alaska just 12,000 years ago."

The gray wolf is one of a few large predators that survived the mass extinction of the late Pleistocene. But this research shows that wolves did disappear at that time from northern North America

To study Alaska's ancient wolves, the researchers collected the remains of bones from the permafrost in eastern Beringia. They examined their chemistry and genes.

Remarkably they found that these late-Pleistocene wolves were distinct from modern wolves. They had different genes and different bodies.

None of the ancient wolves had exactly the same genes as modern wolves, the researchers report. Their skull shape and the way their teeth had worn down showed they were specialised hunters and scavengers. Chemical analysis of the wolf bones confirmed this.

The wolves fed on extinct megafauna, like the bison, mammoth and woodland muskox.

The ancient wolves had large teeth, broad skulls and short snouts, says Van Valkenburgh. This gave them very strong bites. Their teeth were often worn-down or broken. This strongly suggests "regular and frequent bone-cracking and bone-crunching behaviour."

All this came in very handy in ancient Alaska. Wolves there faced stiff competition for food from other fierce competitors. These included lions, short-faced bears and sabre-tooth cats.

When food is scarce modern wolves eat more of their prey, including the bones. They also eat faster which makes broken teeth more likely.

The extinction of this specialised wolf could be a sign of things to come for today's specialised predators, Van Valkenburgh says.

One example is a North American gray wolf that was discovered only recently. It is unusual because it is nomadic. Packs of these wolves migrate with the caribou across the North American tundra. All other wolves have their own territories and do not migrate.

"Global warming threatens to eliminate the tundra, and it is likely that this will mean the extinction of this important predator," says Van Valkenburgh.

More help with words


















What's it all about?

  1. Where in the world did these wolves live?
  2. Is this type of wolf still alive today?
  3. What happened to them?
  4. Which one word near the start of the story tells what happened to them?
  5. How often did these Alaskan wolves kill prey larger than themselves?
  6. If wolves had not survived in Europe what might have happened in North America?
  7. How long ago were these Alaskan wolves alive?
  8. What parts of the wolves' bodies did the researchers study to learn about them?
  9. These wolves were different from today's wolves in several different ways, the scientists found. State one of them.
  10. Three different pieces of evidence showed that the wolves were specialised hunters and scavengers. State two of them.
  11. What did the wolves eat?
  12. How did the scientists work out that the wolves crunched bones?
  13. In your own words what does "stiff competition" mean?
  14. In what kind of conditions do modern wolves behave like these ancient wolves?
  15. Are most wolves nomadic or territorial?
  16. In one sentence what does this mean?
  17. In one sentence why can being specialised sometimes be a problem?
  18. If the weather or the supply of food changed, would an animal that was specialised be more or less likely to survive?
  19. What change do you think happened that made these Alaskan wolves die out?
  20. If you were these scientists what research would you like to do now?
  21. What question would that research be trying to answer?

Topic for discussion, research or pupil presentations

Discovery School has a nice lesson on Ice Ages and extinctions. Its learning objectives include the following.

Students will:

  • understand what causes ice ages;
  • learn about plants and animals that lived during the Ice Age;
  • understand why certain Ice Age animals became extinct.

Here is an extract:

Tell students that they are going to conduct some research about the Ice Age and the animals that lived during that period. Divide students into five groups. Each group will be working on the three questions listed below... Visit the Web sites provided with each question for essential background information. Brief answers are provided in italics.


Question 3. Why did many animals become extinct at the end of the Ice Age? (Although scientists do not know for sure, they suspect the causes are either hunting by people or environmental changes as a result of the warming of Earth. Some researchers think that overhunting by humans eliminated a major species, either the mammoth or the mastodon, which led to more general extinction. Other scientists think that rising temperatures, changing rainfall patterns, and the melting of the glaciers caused many changes to the ecosystem, resulting in the extinction of certain animals.)


Have each group share its findings. What have students learned about the relationship between the environment of the Ice Age and the animals that lived then? What is the relationship between the changing environment of the Ice Age and the animals that became extinct?

Have students complete the Take-Home Activity Sheet: Giving a Scientific Opinion. The purpose of the sheet is to see whether students can apply what they have learned about the Ice Age to modern times. If possible, have students share their ideas with their classmates.

(Note however that some of the links from the Discovery webpage no longer work.)

Tips for science class discussions and groupwork

No 53

Collaborative activities seem to provide less information to the teacher about an individual pupil's progress. This may appear to be a serious drawback for any assessment procedure. However, collaborative discussion, debate and argument are immensely valuable in terms of getting pupils to reflect carefully on their own ideas, to take alternative possibilities seriously and in this way to kick start the learning process.

Naylor, S. and Keogh, B. (2007) Active Assessment : thinking, learning and assessment in science. School Science Review, 88(325), pp 73-79


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