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Bears for Teachers

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Year Rings


The students will be able to:

  1. Figure the age of a bear from the annulation rings in the teeth
  2. Recognize forms of annulation in other species
  3. Relate tooth annulation to the bear's summer food supply and winter hibernation
  4. Create their own annulation map. (year ring map)


  1. Students create their own annulation map
  2. Examine annulations in a bear tooth
  3. Study other annulations in species
  4. Discuss causes of annulation


(Supply information about annulation: why it happens; how it can determine age; other examples of annulation, and what causes the rings in bear teeth). Also supply pictures and/or slides of bear tooth annulations.


  1. A square piece of paper as large as possible
  2. pen/pencil
  3. markers
  4. cross-section picture of bear teeth (several different pictures either copied for the students or put on transparencies)
  5. *If available, bear tooth, a cross-section slice of a tree, a slide or enlarged picture of a fish scale

Ages: 6-12

Duration: 45 min. - 1 hr.

Angry bear


  1. Students make their own annulation maps using a square piece of paper. With a dark, finetip marker or dark pen, students follow these directions:
    1. Make a small dot in the middle of your paper (needs to be fairly accurate).
    2. Make more dots in a horizontal line to the right of the center dot. Make a dot for each year of age until you reach your present age. You may have to go back and make some dots in between. They do not need to be exactly even in spacing. (Teacher should model on the board or the overhead projector) (Square drawn in showing dots)
    3. Place your pen on the first dot after the center dot. Make a circle around the center dot. Place your pen on the next dot and draw a circle around the previous circle. Continue until you've used all your dots. (Teacher models: square drawn with circles inside)
  2. If the center ring were your first year and each consecutive ring the next year, find the summer that was your favorite. Mark that ring by coloring it in with your favorite color. (Example: year 8 was favorite) Box shown.
  3. Bears must have good summers every year in order to survive winter hibernation. They also have age rings similar to the ones you have made. In what part of their bodies do you think these rings are found? Show tooth, if available. Show, or give picture of tooth cross-section. Count the rings.
  4. Discuss the rings annulation and the parts hibernation and food supply play in each ring of annulation.
  5. Show more teeth pictures. Have students figure the age of the bears by counting the rings.
  6. Students give examples of annulation rings in other species. If available, show sliced cross-sections of trees, and/or enlargement of fish scale, or other examples of annulation.
  7. Students finish their own annulation (year ring) map by coloring or making each year ring different to indicate a highlight of that year. (For example, perhaps the student's eighth year was special because he received a bike. They could color the ring the color of the bike or make a bike design in the ring). Let them be creative.


Figure bear's age from picture(s) of bear tooth annulation. Name three examples of annulations in nature. Identify causes of tooth annulations in bears. Finish their own annulation map designs.

Many thanks to Idaho Fish and Game and Project WILD for all of their help in this project. Information for this site developed from "WILD ABOUT BEARS", and is copyrighted by Idaho Department of Fish and Game and Idaho Project WILD. Permission obtained and granted to use this material for educational purposes. Photographic images were provided by the Department of Fish and Game and various other sources.

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