Chapter 6F

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Transcript Chapter 6F

Biology 484 – Ethology
Chapter 6 – Behavioral
Adaptations for Survival
Chapter 6 Opener Canyon treefrogs rely on camouflage to protect themselves from predators
Camouflage is a classic
way of being protected
from predation.
Figure 6.1 Mobbing behavior of colonial, ground-nesting gulls
Mobbing behavior
offers protection to
young in nesting sites
by the adult silver gulls.
Figure 6.2 A nesting colony of black-headed gulls
The behavior of colonial living affords many benefits (and challenges)
for individuals. Increased changes of survival against predators is a
major benefit.
Figure 6.3 An arms race with a winner?
The competitive struggle for survival is
seen here. The salamander being
consumed actually produces a very
highly toxic poison which protects it from
many predators. In this case, the garter
snake is not affected by the toxin, and
therefore the salamander’s defense has
been thwarted.
Figure 6.4 Does mobbing protect eggs?
The title of this
slide poses the
question….
How would you
answer it from
the graphical
information
provided?
Figure 6.5 Benefit of high nest density for the arctic skua
Note the difference between high density populations and low in terms of
survival of larger numbers of young.
Figure 6.7 Not all gulls nest on the ground
Most gulls are ground nesters, but the
Kittiwake Gull is a cliff nesting species.
What would you predict may have
lead to this behavioral shift?
Figure 6.8 The logic of the comparative method
Figure 6.9 Colonial California ground squirrels mob their snake enemies
Mob behavior in a
mammalian
species is less
common, but
shown here in the
California Ground
Squirrel.
Figure 6.10 The dilution effect in butterfly groups
As population size
increases in this butterfly
species, the risk of
predation for any single
butterfly decreases
markedly.
However, what other
factors may alter this
effect?
Figure 6.12 The dilution effect in mayflies
Convergent hatching
dates, can offer the
dilution effect in many
species.
The next three slides show examples of
behavioral groupings that will result in
increased survival.
For each, can you identify how
protection is occurring?
Figure 6.13 Fighting back by terns and wasps
Figure 6.14 Communal defense by sawfly larvae
Figure 6.15 A group of sleeping bees
Figure 6.16 Cryptic coloration depends on background selection
Crypsis is to have features or colorations that allow an organism to
be masked or hidden in its environment. Here we see that the
background selection is CRUCIAL in this protection. Think back to
the “Thinking Like A Predator” lab experience for further comparison.
Figure 6.17 The camouflaged moth, Biston betularia
This is the same classic
species studied to suggest
population change as a driving
force in evolution.
Figure 6.18 Predation risk and background selection by moths
Figure 6.19 Cryptic coloration and body orientation
Interestingly, sometimes
the crypsis is quite specific
and as in this case, is
highly dependent upon
position behaviors held by
the moth in this image. If
the moth were to adopt a
different position (which it
typically does not) when
alighting on the bark, it
would less cryptic.
Figure 6.21 Safety lies in false edges
Lines can be used to blur or highlight
position of animals.
In B, the prominent dark/light patches
blur the full position of the grasshopper,
even suggesting a head region that a
predator may anticipate to follow in a
particular direction.
In C, the bold
patches are
across the entire
grasshopper
(which is toxic)
to help
announce its
presence to a
predator for
protection.
Figure 6.22 Personal hygiene by a skipper butterfly larva may be an antipredator adaptation
The cleaning behavior this
species engages in has
been associated with
lowered rates of
predation.
Glass beads serve as a
non-odor bearing control
equivalent to the leaf
shelter containing many
waste pellets.
In the experiment, there
was no larva present, only
the odor cue of the waste.
The wasp predator clearly
visited and spent more
time at the sites with
waste than those without
waste.
Figure 6.23 Warning coloration and toxins
Each distinctly colored species shown
has a toxin that it is “announcing” it
has via its distinct coloration.
Figure 6.24 Effect of monarch butterfly toxins
Figure 6.26 An advertisement of unprofitability to deter pursuit?
Stotting behavior
in the antelope is
designed to
conspicuously
show predators
that “I am fit and
healthy and
energetic…. I will
be able to outrun
you…. So do not
bother pursuing
me!”
Figure 6.27 Cheetahs abandon hunts more often when gazelles stot
Figure 6.32 Selfish herds may evolve in prey species
A revolutionary work from the mid
1970s that reshaped our ideas about
how to examine selection pressures in
a species.
The key idea is that most every
response an animal makes in its
interaction with its environment (and
hence others in its environment) can
be described in a way that suggests
“selfish” self-preservation of the genes
of the animal.
This was rather controversial in the
70s but is widely accepted as logical
today.
Figure 6.33 Redshanks form selfish herds
Birds of this species that end up being preyed
upon are on average FARTHER away from
neighbors than non-targeted birds, suggesting
a “selfish” behavior.