Announcements:

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Announcements -- For lecture next week, read
Chapters 6 and 7 (now 1-7). -- For lab this week,
read Chapter 9 (Using the Library and
Scientific Literature) -- ALSO, for the lab,
read the paper posted on the website by Erichsen,
Krebs, and Houston (1980). This paper tests the
model I presented last week, using . . . Great
Tits on a conveyor Belt. (Get over the silly
name). ?It will be discussed in the labs this
week!
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Lots of talks this week Wednesday, January 21,
400 pm, 208 BIOSPECIAL ECOLOGY AND EVOLUTION
SEMINAR, "Climate change and coral reef
resilience are we expecting too much from marine
reserves?," Dr. John F. Bruno, University of
North Carolina, Chapel Hill Thursday, January
22, 700 pm, FSU Coastal and Marine Laboratory
Auditorium, St. Teresa, FloridaCOASTAL AND
MARINE CONSERVATION LECTURE, "Florida's coral
reefs threats, decline, management, and signs of
hope," Dr. John F. Bruno, University of North
Carolina, Chapel Hill. Refreshments will be
provided. Friday, January 23, 200 pm, 327
OSBBIOLOGICAL OCEANOGRAPHY SEMINAR, "Sticking
with simplicity facile regeneration, versatile
morphology, and diverse collaborations promote
persistence of the most basal metazoans," Dr.
Janie L. Wulff, Department of Biological Science,
FSU Friday, January 23, 400 pm, 1024
KINECOLOGY AND EVOLUTION SEMINAR,
"Context-dependent streak spawning in a
simultaneous hermaphrodite, Serranus
subligarius, Mia Adriani, Department of
Biological Science, FSU.
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• I. Purpose of this Course
• II. The Scientific Method
• What are Foragers?
• Decision Making by Foragers
• A. Types of decisions
• B. Balancing Costs and Benefits in Decisions
• C. Optimal Diet Model
• Ei/hi gt E/(sh)

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low
Optimal diet model would predict that as prey
become more abundant, predators should become
more picky (specialists).
50
75
200
300
350
I -largest Daphnia prey IV - smallest Daphnia
prey Clear area -- actually eaten Stippled area
-- random eating
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• IV. Decision Making by Foragers
• A. Types of decisions
• B. Balancing Costs and Benefits in Decisions
• C. Optimal Diet Model
• 1. Logic
• 2. Mathematical Model
• 3. Predictions
• 4. Evidence an example with fish
• 5. Other factors to consider
• a. sampling
• b. switching
• c. competition
• d. predation

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5. Other factors to consider a. sampling b
. switching c. competition d. predation --
sampling This theory requires that foragers
know the costs and benefits of their prey. They
can only do that if they occasionally sample all
the prey. -- switching some prey require some
time for the predator to learn how to catch.
This learning can depend on the density of the
prey. -- competition Resource competition just
affects prey density, which doesnt change the
basic theory. Interference competition can leave
the predator with less time to forage, forcing
more of a generalist diet. -- predation can also
affect when and where a forager looks for prey,
forcing more of a generalist diet.
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• I. Purpose of this Course
• II. The Scientific Method
• What are Foragers?
• Decision Making by Foragers
• A. Types of decisions
• B. Balancing Costs and Benefits in Decisions
• C. Optimal Diet Model
• D. Spatial Distribution of Resources
• We have been considering WHICH prey to take.
  Sometimes is may also be important to understand
  WHERE to forage. Many models and experiments
  have attempted to predict or understand the
  spatial components of foraging.

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• D. Spatial Distribution of Resources
• 1. The Ideal Free Distribution (IDF)
• -- WHERE to forage depends on both the number of
  prey and competition among foragers.
• -- IDF states that animals disperse to equalize
  energy intake or reproductive success

Milinski, M. 1979. An evolutionarily stable
feeding strategy in sticklebacks. Zeitschrift
fur Tierpsychologie 5136-40. Placed 6 fish
(sticklebacks) in tank and fed at different rates
at each end of fish tank.
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51 food ratio
21 then switch to 12
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• D. Spatial Distribution of Resources
• 1. The Ideal Free Distribution (IDF)
• -- so fish are smart and conform to
• IDF. Other studies have generally
• found similar results.
• Harper DC, 1982. Competitive foraging in
  mallards ideal free ducks. Anim Behav
  30575-84
• However, the IDF doesnt always hold. Why not?

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• IDF assumes that all individuals are equal. But,
  differences in competitive ability can lead to
  deviations from the IFD expectations. Dominant
  individuals get more than the predicted share of
  the resources.

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• I. Purpose of this Course
• II. The Scientific Method
• What are Foragers?
• Decision Making by Foragers
• A. Types of decisions
• B. Balancing Costs and Benefits in Decisions
• C. Optimal Diet Model
• D. Spatial Distribution of Resources
• -- more in labs on Marginal Value Theorem
• E. Lots of other models you may encounter
• in your reading!

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• I. Purpose of this Course
• II. The Scientific Method
• What are Foragers?
• Decision Making by Foragers
• Dynamics of Forager-Resource Numbers

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• V. Dynamics of Forager-Resource Numbers
• A. Dynamics of predator and prey are tied
• 1. When prey increases, predators can reproduce
  more, increasing their numbers as well. This
  drives prey numbers down, which results in fewer
  predators.

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• V. Dynamics of Forager-Resource Numbers
• A. Dynamics of predator and prey are tied
• 1. Predator and prey numbers linked
• a. use PopDyn
• b. Example Huffackers mites

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b. Example Huffackers mites
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• V. Dynamics of Forager-Resource Numbers
• A. Dynamics of predator and prey are tied
• 1. Predator and prey numbers linked
• 2. We can show this mathematically by
  constructing simple equations
• Growth rate of prey (H)
• dH/dt rH - cHP
• Growth rate of predator (P)
• dP/dt ecHP - mP

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• 2. We can show this mathematically by
  constructing simple equations
• dH/dt rH - cHP
• dP/dt ecHP - mP
• You do not need to memorize these equations. But,
  you need to understand that they are linked the
  predator and prey abundances depend on each other
  in characteristic ways.
• Some implications of these equations.
• -- what is c and what behaviors are related to
  it?
• -- what is e and what behaviors are related to
  it?
• -- are r, c, e, m, really constants?
• -- what happens if P 0? H 0? Is this
  realistic?

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• V. Dynamics of Forager-Resource Numbers
• A. Dynamics of predator and prey are tied
• B. Behaviors Associated with changes in
• numbers.
• 1. c and prey abundance
• -- is c a constant?
• Lets hold the abundance of predators constant
  and increase the number of prey. Does the
  per-predator consumption of prey increase
  directly as a function of P?
• A simple experiment can resolve this question.

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• 1. C and prey abundance
• Clearly, at some point the predator becomes
  satiated and cannot capture anymore prey and so c
  is not a constant at all. The form of the curve
  we created is called the functional response
  curve. This curve was initially derived by C.S.
  Holling who blindfolded his secretary and had her
  forage for sandpaper disks.
• Holling suggested that there are three types of
  curves
• -- Type I
• -- Type II
• -- Type III

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Who cares about these response curves? Well, for
example, they are important for understanding
those oscillations that predator and prey have.
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As Huffakers work shows, the oscillations can
cause either predator or prey to go extinct
(often both). Behaviors that prevent predator
and prey numbers from overshooting one another
will stabilize predator-prey dynamics, allowing
both to coexist. -- The learning or switching
component of the Type III curve can actually lead
to stabilized P-H interactions.
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• V. Dynamics of Forager-Resource Numbers
• A. Dynamics of predator and prey are tied
• B. Behaviors Associated with changes in
• numbers.
• 1. c and prey abundance
• 2. c and predator abundance
• -- predator abundance can also influence foraging
  behavior. Examples suggest that c may go up or
  down.
• -- negative relationships between feeding rate
  and predator density occur when there is
  competition interactions between predators.
• -- positive relationships between feeding rate
  and predator density occur when there is group
  foraging behaviors, such as with organized
  predators (birds flocking and fish schooling).

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• V. Dynamics of Forager-Resource Numbers
• A. Dynamics of predator and prey are tied
• B. Behaviors Associated with changes in
• numbers.
• 1. C and prey abundance
• 2. c and predator abundance
• 3. Refuges and patch dynamics, read
• in the book. Be ready for lab!

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Example Study Chase, J. M. 1998. Central-place
forager effects on food web dynamics and spatial
pattern in northern California meadows. Ecology
791236-1245 A pattern is observed between
lizards, their grasshopper prey, and the plants
eaten by grasshoppers
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• Is this pattern caused by a trophic cascade
  from foraging lizards?
• What else might cause this pattern? Could it be
  shading around structures? Wetter soil?
  Temperature changes?
• How would we test the idea that lizards are the
  most important factor?

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They set up exclosures where they could keep out
lizards. To determine if it was the exclosures
or the structure that caused any pattern, the
experiment was repeated with and without
structure nearby.
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They also looked for the expected effects of
lizards on plants, but in this case, the
exclosures could keep out lizards and
grasshoppers (plants only) or only lizards.
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Would similar spatial patterns be expected for
other types of foragers? -- must be a
central-place forager with a constant home
territory. -- primary effects expected for
herbivores, but secondary effects expected for
true predators. -- effects may be different for
each species. Chase showed his effect primarily
on forbs, not grasses.