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Behavioural Ecology - Predator/Prey (Lectures 6-7)

Terms in this set (22)

1. countershading
2. shadow and edge hiding
3. disruptive coloration
4. hiding the eye
5. appropriate substrate
principles of crypsis
countershading; caterpillar
form of crypsis by being light beneath and dark above to counteract the light from above and shadow beneath to make the animal look flat. fine stripes and spots are often used to blend the join between the two halves. example?
shadow and edge hiding; Wobbegong sharks
form of crypsis where flanges around the edge, alignment in relation to the sun, and flattening of body may be used to hide the body's shadow. Example of animal using irregular lobes to fit closely to the substrate?
disruptive coloration; zebras
form of crypsis where blocks of colour run over the edge of the body to break up the outline and distract the eye from the overall shape. works best against a complex background of the same size blobs. example?
coloration, grain size, shape, orientation (dead leaves), posture (gecko), and incident light (spotted lighting for giraffes)
the animal must be stationary and on the correct background for crypsis to work. this appropriate substrate includes
1) You can't move when predator present: so waste time away from eating, breeding etc.
must see predator before it notices you
2) Must be on correct background: restricts you to one area (unless you can change colour), orientation on that background also needed
3) Requires persistence of your adaptive background: e.g. Peppered moth (Biston betularia) not adapted to blackened trees
costs of crypsis
1. Distract predator with alternative food e.g. gulls regurgitate their last meal if attacked
2. Redirect attack to less important part e.g. caterpillar has false eyes on rear end of body
3. Startle the predator into hesitating in attack e.g. sun bittern uses false eye displace to startle and drive off crocodiles
4. Drive predator away e.g. gulls mobbing crows that enter their nests to distract crow's attention and protect eggs
what the prey animal can do once the predator has seen it
fear scream
a scream that animals make when caught to summon other predators
1. hide
2. run away
3. be inedible
4. pretend to be inedible
4 methods to deal with predators
1. using physical defenses (size, spines, armour)
2. using chemical defenses (toxins) that are either synthesized from raw materials or sequestered from food
2 methods of being inedible
warthogs and wombats
animals that use plates of solid bone as armour inside their skin
sea slug
animal that sequesters toxins from the jellyfish it eats
cardiac glycosides
a heart poison that monarch butterfly caterpillars get from eating milkweed. causes predators to throw up when they eat the butterflies
aposematism; gazelles stott to show they are healthy and unprofitable to chase
Warning signals allied with a toxin (or other unprofitability such as physical toughness, quickness). example?
multimodal signals; lady bugs reflex bleed a liquid that smells like pyrazine and is bitter
signals that combine different senses including warning colouration, sound, odor, shape, pattern. example?
Group 1 : washed ladybird wings stuck onto a palatable beetle
Group 2: Palatable beetles offered in a perforated dish placed over a source of pyrazine odour
Group 3: palatable beetles with the taste in the form of reflex blood spread over otherwise palatable beetle.
Single signals differed in their effectiveness:
Colour > taste > smell
But none of the signals were lastingly effective alone.
lady bug experiment
mullerian mimics
unprofitable species sharing the same signals despite being only distantly related; result of convergent evolution. They share these signals to reduce the number of signals the predator must learn
thanatosis; possums
appearing to be dead as a way to pretend to be inedible. example?
masquerade; copying leaves
type of crypsis that copies a specific inedible object to pretend to be inedible. example?
batesian mimicry
edible prey copying the signal of aposematic animals to pretend to be inedible
dietary conservatism
very prolonged aversion to adding new foods to diet (longer lasting than neophobia). Genetic.
blackbirds and robins
Blackbirds and robins were first familiarised with eating pastry of a particular colour...
...and then given the choice of familiar and novel colours in successive presentations
Many birds showed strong, prolonged avoidance of novel prey (100+ presentations)
dietary conservatism experiment by Marples
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