PROCEDURE:
Activity : 20 minutes
Prey items are placed in a box. Students act as predators and select prey
items of differing point values within a fixed time. Some prey items perfectly
match the background (+10 points), others partly match the background (+5),
others are aposematically colored (-10), and others are mimics of aposematic
prey (+10). Over a 15 second time period the predator picks up a prey item
and looks at the point value on the back, places it to the side, then selects
again until 15 seconds have passed. The teacher can act as time keeper. After
each student has had a chance to be the predator, he or she records their score.
Next, each student, now experienced, tries again. Students have now learned
from observation that there are different points for different color patterns.
Do a third and forth trial if time permits. Tabulate the score for all students
for their 1 st turn, 2 nd turn, etc. Arrange the scores from lowest to highest.
Calculate the average for 1 st turn, 2 nd turn, etc. Count how many times each
score was achieved and draw a histogram of scores for 1 st turn, 2 nd turn,
etc. Discuss.
Scenarios :
Several scenarios (varying numbers of cryptic, model, and mimic species; and
naïve vs. experienced predators) can be used to illustrate different points.
Less complicated scenarios (such as the full mix model below) can be used as
a general illustration of predator-prey dynamics when prey items vary in value.
To explore more complicated scenarios, the proportion of models to mimics can
be manipulated to demonstrate predator learning when models are more or less
abundant in a batesian mimicry system. To demonstrate mullerian mimicry, multiple “species” of
aposematically colored species can be placed among palatable species.
• Full Mix Model of cryptic, model, and mimic
species
• 6 aposematically colored models (-10 points each)
• 2 mimics (+10 points each)
• 4 perfectly cryptic specimens (+10 points each)
• 8 partially cryptic specimens (+5 points each)
• Compare scores for naïve (first time) vs. experienced predators
• Varied Batesian Model (vary the proportion
of models to mimics)
• Models more abundant (5 models for each mimic)
• Models less abundant (5 mimics for each model)
• Add 10 partially cryptic species (+5 points each)
• Models = -10 points each, mimics = +10 points
• Compare scores for “model-rich” vs. “model-poor” scenarios
• Mullerian Model (several nonpalatable species)
• 5 brightly colored red & black (-10 points each)
• 5 brightly colored yellow & black (-10 points each)
• 5 brightly colored orange & black (-10 points each)
• 1 mimic of each of the three above (+10 points each)
• 10 partially cryptic species (+5 points each)
• Compare scores of naïve (first time) vs. experienced predators
• Natural Selection Model (do better mimics survive
more to reproduce?)
• Using individuals of varying crypticity, see which survive predation
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