SKILL FOCUSConducting researchPerforming and recordingAnalyzing and interpretingInvestigation 13•A
Chapter 13 Ecological Principles • MHR 437Pre-lab Questions
Identify at least one species that is considered a
specialist.
Identify at least one species that is considered a
generalist.
What are some of the advantages and disadvantages
of being a specialist or a generalist?
What criteria would you use to evaluate the success
of the two methods of foraging for food?Problem
Identify differences between the foraging strategies used
by specialists and generalists.
Predictions
Predict differences in the foraging behaviour of
generalists and specialists. Also predict which type
will be the most successful.
CAUTION: Wash your hands when you have
completed the investigation.
Materials
plastic dishpan (or other stopwatch
similarly sized container) graph paper
sand sieve
dried beans (40 kidney beans,
30 pinto beans, 20 lima beans)
Steps 1 and 2
Procedure
Part A: One Species of Prey
1.Fill the dishpan one-half to three-quarters full of sand.
2.Bury 40 kidney beans, 30 pinto beans, and 20 lima
beans in the sand. None should be visible on the
surface.
3.Design a data table that will allow you to record an
identifying number for each forager, the number of
prey items (beans) remaining buried before each
forager begins searching, and the time taken by
each forager to find enough beans to ensure survival.
4.Appoint one member of your group as the “referee”
prior to the first turn. This person will time the first
foraging trial and ensure that each forager abides by
the foraging rules (step 5). The position of referee
should be rotated so all members of the group have
an opportunity to forage.
5.Foraging must be done with one hand only, and
care must be taken not to remove any of the sand
from the pan along with the beans. No one but the
referee can watch the current forager (the other
group members must turn their backs).
6.When the stopwatch starts, the first forager begins
searching for beans. He or she has 10 seconds to
find three beans — the number required for survival.
Immediately after the beans are located, foraging
stops. If the forager cannot find three beans, he or
she dies of starvation and is eliminated. As each
prey item is located, it must be placed in a container
beside the pan immediately after capture. (This
simulates the time it takes for a predator to handle
— kill and/or eat — its prey).
7.The referee records in the data table the time taken
to find the prey, smoothes over the sand after each
turn, and ensures all remaining beans in the pan are
buried before the next forager takes a turn.
8.Repeat steps 4 to 7 until all foragers in your group
have died.
9.Produce a graph showing the relationship between
the time taken to find three beans (dependent
variable) and the number of beans remaining in the
pan (independent variable).
Continued on page 438 ➥Foraging Strategies —
A Simulation Experiment
In this investigation, you will compare the foraging (feeding) strategies of
specialists and generalists by doing a simulation experiment. You assume the role
of a forager — perhaps a predator — and various types of beans will be your food
or prey. A pan of sand will simulate the habitat in which you live and look for food.