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Chapter 5
Primary = Operates whether or not predator is
there. – Decreases probability of an
encounter with a predator
Secondary = Once detected by predator increases probability of surviving encounter
Ex. Noctuid moths - A1 receptors = primary; A2
rec. = secondary
1. Crypsis (camoflaging)
a. color pattern
 Body color: Many animals are cryptically colored
to blend in with their environment - fawn brown with white spots, make it blend in with
patches of sunlight on forest floor

Disruption patterns: may break up
animal's shape or discernable features
ex. stripe across eye of frog
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Color and body form - mimic leaf, stem, thorn
behavior reinforces color pattern
1. animals remain still or may move to mimic
object blowing in the wind
2.
body orientation: important if color pattern
must be aligned with that of background
Ex. if mimicing a thorn, thorn must be aligned
with others
Ex) African cicida
moth (Ityraea)
mimics a flower, a
group clusters on a
flower stalk (all
oriented the same
way) mimicing an
inflorescence
(group of flowers)
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Not only is the color pattern, but the behavior
is an adaptation
Jays trained to peck at Catocala relicta
moths for reward
 10-20% reduction in
“capture rate” if on pale
birch bark & positioned
with head up.
2. Bluff - look like what you are not
a. mimic predator's predator - snake
b. something distasteful - bird
excrement
c. again behavior is important
- correct orientation or sway body
3. Aposematism - warning coloration
= warning of a distasteful or dangerous quality
predators usually have to learn this pattern.
Ex. Monarch, coral snake complex = color
Ex. wasps and bees - yellow, or orange and black
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Cost – Benefit analysis can be used to study
conspicuous coloration and behavior.
Tephritid flies wave conspicuous wings – How
is this adaptive?
 Looks like jumping spider
 T. flies with clear wings
were eaten
 House flies with T wings
were eaten as well
 Wings & behavior needed
1. Misdirection of attack
a. false head- lantern bug
- hairstreak butterfly
b. Asian web-building
spider (Cyclosa) builds a
platform where it sits
ready to pounce on prey
and 2 pseudo-platforms.
2. Distraction
 hind wings – eyes, bright color
 hiss - cockroaches
3.Defensive secretions
a. ant guards (wasps, bees)
Ex. Polistes, Polybia
b. sticky solution, (black widow spider, termites)
Ex. Nasute termites - heads like guns in soldier caste
Ex. black widow spider - eaten by mice - spider if touched,
immediately secretes web with sticky droplets on it - smear in face
of mouse. The time it takes the mouse to get rid of sticky mess,
spider has opportunity to escape
c. chemical repellents (Bombardier beetle, sting, poison toads,
salamanders etc)
Ex. Bombardier beetle - 2 glands combined = explosive reaction burning chemical
Ex. Eucalyptus sawfly larvae
Ex. Sting – scorpions, bees, ants, etc.
4. Evasive behavior
 flight or withdrawal - into burrow or other
retreat
5. Group defense
A. mobbing of predators  small birds such as starlings attack larger
predatory birds - hawks. Seem to endanger
themselves. But seem to so distract and harass
predator that it seems an effective way to drive
off predator or cause it to miss seeing prey.
 group attack in stinging insects - more effective
too
a. sting chemical attracts others to join in
attack
B. Group position
1. musk oxen - stand in circle; pods- young to center
C. Benefit of just being in a group
1. predator can only capture so many - saturate predator
- mass emergences of insects
- large herds of animals or schooling in fish
2. more eyes
3. better to hide behind someone else - Selfish herd
hypothesis (W. D. Hamilton)
a. what may look to be a cooperative flock or herd,
may really be many selfish individuals - all trying to
hide behind someone else
6. Get help from symbiotic relationship with another species
- aphid and ants
6. Get help from relationship with another
species
- aphid and ants (symbiosis)
- large and small nesting wasps
(commensalism)
The goal of most animals is to manage to get enough food to sustain
life and reproduce.
feeding behavior requires an expenditure of energy (cost)
Animals should try to reduce the cost of feeding while trying to
maximize the net gain in energy (which can then be put toward
reproduction)
Net (energy) gain = Food acquired - energy required to get it
(benefit)
(cost)
(in this society, cost is so low, we often have a problem from the net
gain in energy which we store as fat)
Remember: animals should behave optimally by
maximizing gain and minimizing costs
Ex. Crow foraging by Reto Zach
 Crows - seashores eat shellfish
Assumption: Crows are foraging optimally so as to
maximize benefit while minimizing cost
Hypothesis: Benefit = amount of whelks eaten/
time; Cost = energy used to fly to a height for
dropping the whelk to break it open
Number of Drops per Whelk
100
90
80
70
60
50
40
30
20
10
0
Ht. of Drop (m)
Calories gained (benefit) by eating whelks of different sizes could
easily be measured.
Results:
Only large whelks would break open easily enough and provide
enough energy (calories) for the crows to gain a net amount of
energy. If crows forage optimally Prediction 1: Crows should only feed on large whelks and ignore
small ones.
Tested by providing crows with a selection and recording which they
took.
Results: When given a selection, crows ignored all but the largest
whelks
Prediction 2: crows should choose a dropping
height that will minimize the total
expenditure of energy.
Total Ht./ Whelk (m)
Figure below estimates this: at ht of 5 m drop, may have to drop 4 times
to open = tot. 20m; at ht of 7 m drop, may have to drop 3 times to open =
tot. 21m
120
100
80
60
40
20
0
1
3
5
7
9
Ht. of Drop (m)
11
13
15
Greater the height Whelk may bounce away and be lost
 Another bird may have time to reach prey first
So birds should use the lowest dropping height
possible for maximum gain.
Looking at previous graph – Zach predicted
average height of drop would be around 5.5 m.
Total Ht./ Whelk (m)
120
100
80
60
40
20
0
1
3
5
7
9
11
Ht. of Drop (m)
Conclusion: The crow does indeed seem to be
programmed (genetically predisposed) to
choose the size of whelk and the dropping
height that maximizes its net energetic profit.
Since the crow's behavior fit the predicted
pattern, the constraints on the behavior
identified by Zach appear to be correct.
Factors: 1) size of whelk, 2) energy spent in
flight, 3) competition, 4) loss of whelk if dropped
from too high
13
15
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Similar study
Energy model would predict largest
mussels would be chosen
Not supported
Hypothesis: some large mussels can’t
be opened, model modified to account
for longer average handling time.
 Prediction – 50 mm average

Hypothesis rework: barnacle coverage
on largest mussels makes these
impossible to open – these should be
avoided
 Model predicts 30-45 mm average
Marginal Value Theorem
 longer in the patch, the less the return in food
Net
Return
Time in Patch
When should an animal decide to go to a new patch?
 depends on time to locate and travel to a new patch
 optimum time to move is when the max. gain is attained
Net
Gain
A
B
Time to Move
Between Patches
0
B A
Time in Patch
1. nutritional constraints on foraging
Animals do not just need calories (energy). Variety
may be important to get a full range of needed
nutrients.
Often a particular mineral or amino acid may be in
low concentration in normal diet. Animal must
make a special effort to feed on a particular food
or consume enough of its normal diet to get the
limiting mineral or amino acid.
1. Lycosid spiders consume a variety of small prey (not
high energy yield). But lycosids on a varied diet
reproduce better than those maintained on a diet of a
single prey species. (9 essential amino acids can't be
synthesized and are needed from diet).
2. Moose - terrestrial plants - high energy but aquatic
plants - high sodium (which is limiting)
3. Aphids - feed on plant phloem - high sugar content,
but low amino acid content; Aphids must feed a lot;
excess sugar given off (why tended by ants)

This may force animals to search out and
feed only on certain plants and animals that
have lower toxin levels
Example: Tassel-eared squirrels - feed on bark
of ponderosa pines. Variation in amounts of
terpenes in trees.
Animals may not always appear to be foraging
efficiently. There may be trade-offs between the
value of a particular foraging method and some other
less obvious cost, such as danger from predators
Example - Juncos (seed eaters and prey of hawks)
while feeding, juncos stop and look about 15X /min
Often feed in flocks (increased competition, but more
eyes and the less time each must spend looking)
- this changes, if a predator is in the area, juncos singly
or in flocks will spend more time looking

Dugongs feed on sea
grass
 Grazing on grass tops
▪ Good visibility
 Rooting up the
holdfasts (excavation)
▪ Poor visibility
▪ High nutrition

Presence of sharks
 Impacts foraging
Example: small bird - good seed patch (might
not last), spends some time checking out
other seed patches even though good patch
is all it needs
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If animal does not have exclusive access to
food patches, the density of competitors
might change duration in a patch.
May also result in selection favoring territorial
behavior and the defense of
patchy resources.
Herbivory: feed on plants, which = primary level of food production
Plant defenses: (when predation not wanted)
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Mechanical: hairs with hooks, thorns, tough outer coating
Chemical:
a. reduce digestability
Ex. tannins, silica:
b. cause nausea or death to those who feed on them
Ex. pyrethrin (natural insecticide), cardiac glycosides (milkweed)
c. hormones - interfere with insect development and reproduction
B. In response, different animal species have evolved ways of getting
around specific plant defenses
1. plant mechanical defenses
 Passiflora adenopoda hooked hairs on leaves - butterfly larvae get hooked
and die
all except one which specializes on this plant
= Mechanitis isthmia – butterfly larvae feed in groups and they spin a web
covering over the hairs and feed together on the exposed edges of the
leaves.
2. chemical defenses - such food has few competitors => good resource

some animals' physiology has evolved to deal with particular plant defenses animal usually becomes a specialist - feeding on only one or 2 plants
ex. Monarch butterfly - milkweed
(evolved a tolerance for the cardiac glycosides - stores toxins in its own
tissues)
ex. horses and cows can feed on grass, our teeth would wear down rapidly due to silica in plant tissues
Plants may ‘want’ animals to feed on them:

For pollination (pollen houses developing
male gametes) - transfer of pollen to female
organs of another flower.

seed dispersal - animal eats fruit, flies and
disperses seeds
Plant provides nectar to attract pollinators - they will carry the plant's
pollen to a neighboring plant - of same species.
Plants have evolved structures that ensure that only one or a few species
can pollinate them. These animals will in turn tend to specialize.
Ex. different types of flower mechanisms
 Flower structure: Nectar may be down a long tube, which only bees with
long tongues can reach
 Some have nectar sources hidden in capsules that will open only if a
sufficiently heavy insect alights upon the flower.
 Flower color: red – moths and birds; white – nocturnal; UV – bees, wasps
Ex. Timing of flower opening

Day versus night
Ex. Small nectar flow may tend to attract smaller insects
1.
2.
Attractive fruits, seeds
Various attaching devices
As animals feed and move around, they help to
disperse the progeny of the plants
An entire area of research deals with animalplant interactions.

Internal
◦ Modified for entering body – may involve multiple
life stages, with only some parasitic
◦ Parasitoids – lay one egg, which multiplies in host
◦ Usually pale and small

External
◦ Usually have structures for holding on or moving
through hair
◦ Flattened to be against body, small, match host


Parasitic is a specialized
form of carnivory
Predation
 Chase prey
 Filter feeding
 Aggressive mimicry
▪ Preying mantid = flower or leaf
▪ Fishing with lures : Anglerfish
• Lightning bug females
Photuris female eats males of
Photinus spp.
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Ant lions
Bola spider
Chimps
Archer fish
Woodpecker finch
Egyptian vulture
Sea otters
Whales

http://www.youtube.com/watch?v=1DoWdH
Otlrk
David Wiley, Colin Ware, Alessandro
Bocconcelli, Danielle Cholewiak, Ari
Friedlaender, Michael Thompson &
Mason Weinrich
•Whales create bubble nets by
releasing air while swimming in spirals
or circles.
•They feed on small fish that school or
krill
•Feed by opening mouth, taking in a
large volume of water and filtering
food out of the water as it passes
through the baleen
•Bubble size varies from Atlantic to
Pacific.
Feed in clustered
groups
 Some will add bubbles
to another’s net
 Some may feed within
another’s net; perhaps
in a mutual sharing
 It is possible that some
are stealing from
another’s net.

Benefits of social prey capture:
1. Flocking birds - more eyes to locate food,
transient birds benefit most from knowledge
of residents
2. Kill larger and more dangerous prey than
could be handled by a single individual
2 different extremes:
a. Terrestrial vertebrate
carnivores : cats (lions), dogs
(Wild dogs, wolves), and
hyenas
Ex. Lions - females live in
small groups and hunt
together (occasionally one or
two males)
 Some may act as decoy, others
charge from a different directions
simultaneously
b. Invertebrates: army ants
(more details in 3 wks)
Ex. African driver ants
(colonies 20 million) -swarm
foraging
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Saprophagous and Coprophagous
 http://www.youtube.com/watch?feature=playe
r_embedded&v=q703ArSTDE0
 Feed on dead plant and
animal tissues or excrement

Omnivores