Biology 484 – Ethology
Chapter 7 – The Evolution of
Feeding Behavior
Chapter 7 Opener: A bullfrog has many dietary choices to make
Many choices may go
into what types of
food an animal eats:
• Caloric needs
• Other nutrient
needs
• Availability issues
• Risks associated
with certain foods
(location, etc)
• And many others
The Common Whelk (or Snail)
7.1 Optimal foraging decisions by northwestern crows when feeding on whelks
The Crow has been studied and show to obtain the maximum cost/benefit ratio
from dropping the snails at a height of roughly 5 meters.
7.2 Available prey versus prey selected
Why would they not preferentially
select only the LARGEST mussels?
7.3 Two optimal foraging models yield different predictions
These two competing
models suggest vastly
different outcomes. In A,
the model is looking at
calories and time spent
opening the snail,
whereas model B adds in
the potential loss acured
when a mussel is so large
that there is a significant
possibility the bird’s
dropping efforts will not be
successful.
7.5 A foraging bout by the red knot
Time line showing how the bird will select to
move to another foraging spot.
7.6 Young garden skinks lower their foraging success in order to reduce the risk of predation
Feeding behavior can be influenced by other
risks, such as that of predation pressures. In
this case, it is snake scent. On the right graph,
the “wood block” category is an environment
that allows hiding places for the skink.
This is an image of the phorid fly on the left. On the right is the end result of
an attack on a fire ant, the main food item of this fly.
7.7 Foraging efficiency is compromised when the risk of predation is high
The forager ant is preyed upon by the phorid fly. But the phorid fly will only
consume insects with a head size of 1.8 mm or greater. Hence, during
predation times, the forager ant only sends out smaller (less efficient foragers).
7.8 Records of energy consumption in relation to trotting (red line) versus galloping (green line)
Look for the efficiency of
trotting versus galloping. In
each the actual transition
time is at the point of greatest
efficiency in trotting.
How might you explain these
data?
7.9 How can two hereditary phenotypes coexist in the same population?
7.10 Two hereditary forms of an African cichlid fish
Because their
phenotype differs, the
two forms do not
compete for
resources.
7.11 The results of frequency-dependent selection in Perissodus microlepis
Look at how the actual percentage of the
individuals hovers consistently around a 1:1
ratio of left jawed and right jawed fish.
7.14 Web ornament of an orb-weaving spider
Web
ornamentation
is seen in the
more reflective
regions (the zigzag patterns)
seen in this
web.
7.15 Do web ornaments lure prey?
7.17 A cost of conspicuous web decorations?
7.19 The antimicrobial properties of the major spices
7.20 Clay eating has evolved in several species of parrots
Clay eating is useful for dissipating toxins the birds consume.
7.21 Round dance of honey bees
7.22 Waggle dance of honey bees (Part 1)
7.22 Waggle dance of honey bees (Part 2)
In a dark environment, like
inside the hive… or
anytime the sun is not
present, orientation will be
against the vertical.
7.23 Testing directional and distance communication by honey bees (Part 1)
Test by von Frisch examining
ability to learn direction from
the dance in bees. Most new
foargers correctly went to the
feeding station the dancer
oriented them to with her
dance.
7.23 Testing directional and distance communication by honey bees (Part 2)
A similar test by von Frisch used to test the
communication of distance by the dance language
in bees.
7.24 Honey bee recruits really do “read” the symbolic information in dances
The “blue” bees were
trained to think the food
source was 70 meters
away.
7.26 The adaptive value of the dance communication system (Part 3)
Note especially how the bees in the winter benefit especially in enviornments
with oriented (unipolarized) light.