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11. Using the chalkboard, list “injured,” “blind,” and “mother.” Ask these special beavers
how much food they collected. Write how much food they collected after each of
their descriptions. Then, ask each of the other students how much food they found,
writing each amount on the board. Tell the students now that each beaver needs 56
pounds of food to survive for a week. Which beavers survived? Was their enough food
for all the beavers? How many pounds did the blind beaver collect? What about the
mother beaver? Was she able to collect 112 pounds? What will happen to her kits? Will
she feed her kits first or herself? Why? What would happen to her if she fed the kits
first? Why? What if she only fed herself? If the kits die, can she have more young in
the future? (The mother beaver would feed herself first because of this fact. She
must survive first if she is to hope for any of her young to survive.)
12. If the water squares were included, each student should have picked up at least one
square representing a water source. Otherwise, they do not survive. Water is essential to
all life and is a key limiting factor. Specifically, for beavers, water is necessary for all
components of their natural habitat: the river they swim in, the trees that grow on its
well-watered banks, and the marshes that grow the beavers’ favorite aquatic plant foods.
13. Ask each student to record how many pounds of each type of food gathered. Then,
direct the student to convert these amounts to percentages (if they can). Provide the
students with the background information on the typical diets of beavers (following the
diet chart included and any biology sources you research) so that they can compare what
they collected with the natural diet of beavers. How do beavers’ diets compare to
humans’ diets? Maybe we should take a lesson from them and eat more veggies!
14. Ask the students to arrive at a class total for all the pounds of food they gathered as
beavers. Divide the total by 56lbs. needed for each beaver in order to survive one
week (an approximation). How many beavers can Buffalo Bayou support? Why then did
only ___ beavers survive? What percentage of beavers survived? What percentage
would have survived had the food been evenly divided?
15. Ask the students to calculate how many food squares must be added in order to
support all of the beavers in the activity. If sufficient food were available for all the
beavers, would the population likely increase or decrease? Other than food, what
other factors, natural or human-caused, might also limit the growth of the beaver
population in the bayou? How would each of these factors (food, water, space, shelter,
pollution, etc.) affect the beaver population? Could the beaver population increase
indefinitely if there were unlimited food? There are plenty of trees around the bayou
aren’t there, so why don’t we see more beavers in Houston? What human-caused
factors are hurting beaver populations here? Do you think Buffalo Bayou is important
for beavers’ survival in our region?
16. Now, introduce the important science term they have been learning about: the Limiting
Factor. Based on their discussion, try as a group to define the term, limiting factor.
Have the students discuss limiting factors for other animals, and even humans. Do we
need to be concerned about having enough food and water for our own human
populations? (Yes!)