Lecture 17 Flashcards
To maximize conspicuousness, what do tropical birds use?
patches of red that stand out
against green backgrounds
Vertical jumping displays are what?
against horizontal backgrounds are conspicuous.
Aposematic coloring
used to describe colours and / or patterns that act as a warning to predators that a potential prey species is unpalatable, toxic or dangerous.
What are some species that are both conspicuous and unpalatable to predators?
Arthropods and salamanders.
Species like arthropods tend to form large aggregates to maximize what?
Maximizing saliency
thereby reducing predation
Evolutionary advantage to prey species of
being easily identifiable confers what benefit?
Beneficial for predators to be able to recognize
unpalatable prey
Predators need to learn to avoid aposematic prey, give an example?
Naïve blue jays will readily eat viceroy butterflies
until they eat a monarch, then they avoid both
species
What is a signal?
A perceivable behavior or feature that
has evolved and acquired a specific
characteristic of conveying information about
the signaler or the signaler’s environment
what is a cue?
– A regularity or pattern that is either
permanently ‘ON’ or is ‘ON’ or ‘Off’ depending
on specific conditions
… Cues benefit the receiver exclusively
Ex. Mosquitos fly against CO2 streams to locate
mammals to bite
Aposematic colors as cues?
Warning signals are permanently “ON” and
associated costs are paid early in development
Lygaeid bug (Lygaeus equestris) has two _____
morphs
color (both morphs are equally umpalatable)
Researchers place T. guttata and P. majors in a
ring with both color morphs of lygaeid bug. What did they find?
Birds that were wild-caught rejected prey more often than hand-reared individuals Some prey were rejected after handling whereas other prey were avoided (never handled)
Predator avoidance was a combination of …?
indirect effect of coloration
influenced by predator’s experience.
Sandre found that aposematic signal efficacy might be linked to?
Distinctiveness from undefended prey or
background
Predator’s ability to remember previous encounters
Variation in some predator species can change
selection pressures on coloring. How?
Individual ability to overcome prey defense or toxicity
Individual differences in the unspecific motivation to feed (appetite/hunger)
Describe the Sandre study
P. major were used as predators
Wild-caught and housed for 4 days prior to testing
Boiled meal worm (T. molitor) larvae were
painted based on different color morphs of
lepidoptera (O. antiqua) … Two yellow spots, two black spots
Four brown spots
Mealworms were presented on a white plate. What was done to them prior to presentation?
All mealworms were injected with chloroquine
phosphate to make them distasteful and mildly
toxic
What were the findings of the Sandre study?
Birds hesitated longer in attacking the yellowyellow
morphs than the brown morphs
No difference between yellow-black morph and
yellow-yellow
Attack delay increased with each training trial but there was no difference in learning rate between the different prey color morphs
Birds appeared to learn to avoid the prey
Appetite of the birds significantly impacted the
attack delay. Why?
There was a negative correlation between hunger
and attack delay (hungrier birds attacked
mealworms faster)
The birds showed equal rates and ________ _ ________ for all color morphs
effectiveness of learning
Birds learned to avoid all mealworms with
_________ _____
painted dots
generalized their avoidance easily
What did Gagliardo study?
Studied the impact of gregariousness on prey
avoidance
_______ _______ appears to have evolved
prior to gregariousness
Aposematic coloring
What is a primary hypotheses regarding aggregation?
Aggregation naturally ‘dilutes’ predation risk
Describe the Gagliardo study?
Domestic chicks (Gallus gallus) were trained to eat both yellow and green dyed bread crumbs
Describe the single treatment in the Gagliardo study.
10 birds received 18 green
palatable and 18 yellow unpalatable (treated
with Quinine and mustard) bread crumbs during testing; crumbs were placed singly in 36 different wells in random order
Extinction presented same number of bread
crumbs but both colors were palatable
Describe the aggregated treatment ?
10 birds received the
same number of crumbs but in three
aggregations of six green and three of six
yellow
Describe visually aggregated treatment?
9 birds received same arrangements of single crumbs as in single treatment, but below the clear base of the well were six visually similar crumbs, (only ate on, but saw many)
Describe visual single treatment?
9 birds were offered a single crumb inside the well with one crumb below the clear base (ate one, only saw one)
What were the findings.
Ate more crumbs in the single condition.
Unpalatable prey suffer higher predation if arranged solitarily.
________ ________ is not a function of number of
prey eaten in rapid succession
Taste Deterrence (Aggregate conditions showed no difference in consumption rate)
When did birds eat more newly palatable crumbs?
single treatment extinction phase (Extinction rates would occur more quickly for nongrouped
prey)
Which birds took longer to learn?
Birds in the single treatment condition took
longer to learn to avoid the non-palatable
crumbs
There were no significant differences between
the remaining three groups
What may be the mechanism when deciding if a prey is noxious?
Being able to see prey coloration as the noxious
stimulus is perceived during ingestion may be
the mechanism by which discriminative aversion learning is enhanced
This may support such associated characteristics as larger size, resilience to
ingestion, or expendable parts
Describe the handicap principle
Inducing a disadvantage to the bearer to signal the
ability to overcome the challenge
