Lesson 12: Anti-predator Behavior

Question 1

crypsis

Answer 1

the art of blending in - usually a combination of appearance and behavior

Question 2

examples of crypsis

Answer 2

• grasshopper
• thorn bug
• grasshopper
• walking stick insect
• ## mantid

Question 3

predator avoidance by cryptic colorations
- do crabs actively behave to take advantage of their cryptic coloration —->

Answer 3

Q: dos cryptic coloration actually protect the crabs

• individual juvenile crabs were tethered on ceramic tiles in the ocean that were either a uniform white color or a heterogeneous shell-hash color and then recorded the survival of individuals over time

Results:
- only 30% of crabs on white tiles survived
- over 60% of crabs on shell-hash tiles survived

Conclusion:
YES

Question 4

do crabs SELECT cryptic shell-hash color substrate + EXPERIMENT

Answer 4

• do crabs prefer a shell-hash background to one that is uniform in color
• does predation risk affect preference for background

EXPERIMENT:
- gave crabs choice of resting on white or “heterogeneous” tiles
- manipulated predation risk for half the crabs by adding water from a tank containing predatory fish
- controls were given plain sea water

RESULTS:
- small crabs always preferred the shell-hash
- large crabs showed no preference when the predation risk was low but preferred shell-hash when the risk was high

Question 5

Reducing activity is another way to reduce conspicousness

Answer 5

• do animals reduce their activity to reduce being spotted by a predator?

Question 6

whiptail lizards and reduced actity

Answer 6

• whiptail lizards were placed in large experimental pens
• added 2 predator leopard lizards to hald the pens

RESULTS:
- whiptails in predator-present pens were less active

Question 7

antipredator defense

Answer 7

• sometimes you want to be conspicuous
• misdirection –> distracting the predator

Question 8

misdirection (skink w blue tail)

Answer 8

this species can drop the tail to distract predators

Question 9

misdirection: hognose snake

Answer 9

if crypsis fails,

1.) it flattens its head and acts like a viper
2.) it acts like it is dying in agony
3.) if that fails, it just plays dead

Question 10

warming or aposematic coloration

Answer 10

skunk or poison dart frog

Question 11

avoidance of warning colors: learned and inherited behaviors

Answer 11

• evidence suggests that some predators have an innate avoidance of warning coloration
• but others need to learn

Question 12

innate avoidance by great kiskadee

Answer 12

• great kiskadees are birds found in texas that prey on snakes but avoid the poisonous coral snakes that live in the same area
• researchers asked whether avoidance was innate or learned:

so they hand-reared hatchlings to see if they needed to be taught what was poisonous

Experiment:
- challenged birds with dowels painted with rings and stripes of different colors

RESULTS
- birds raised in captivitt avoided the yellow and red rings and coral snake rings despite never having seen a coral snake before: demonstrates an innate behavior

Question 13

warning or aposematic coloration: learned avoidance

Answer 13

• the monarch butterfly larva feeds on milkweed which contains bitter-tasting and toxic alkaloids – the adults taste nasty to most animals

Question 14

batesian mimicry (mimicking a poisonous animal):

Answer 14

monarch vs. viceroy butterfly

• the small viceroy butterfly on right does not eat toxic plants BUT it looks like a monarch so predators avoid it too

Question 15

batesian mimicry: coral snake vs. kingsnake

Answer 15

coral snakes is venomous but the kingsnake is not venomous but has similar coloration

Question 16

does looking like a coral snake protect kingsnakes from predators?

Answer 16

• staked out plastic snake models in areas with and without coral snakes
• some brown and cryptic others with kingsnake pattern
• checked to see if teeth marks were left in the models and counted predation attempts

RESULTS

• in all areas, the precentage of cryptic snake models that were attacked was about the same, suggesting equal number of predators
• in areas where coal snakes live, the kingsnake models were rarely attacked
• BUT in areas where coral snakes don’t live, predators did attack the kingsnake models

SUGGESTING

• that the pattern of a kingsnake evolved w the presence of coral snakes

Question 17

being conspicuous for pursuit deterrence? Stotting in gazelles

Answer 17

• stotting behavior is probably a kind of alarm signal to other gazelles
• but, gazelles stot even when alone and there is no one to warn
• stotting behavior is also a signal that is readable by other species - and evidence suggests that gazelles want them to read it
• cheetas are warned off when gazelles stot - clearly involved in pursuit deterrence

Question 18

cheetahs abandon hunts more often when gazelles stot t/f

Answer 18

true

Question 19

social defenses in killfish

Answer 19

research question: do fish form schools to protect against predators?
prediction: fish should prefer to associate with larger rather than smaller groups if predation is an issue

Experiment: Used 4 treatments

1.) high predation risk treatment: dilute killfish skin extract added to tank (stimulates predation event)

2.) predation cue and food added to tank

3.) just food added to tank

4.) control: water added to tank

Measured size of schools that the fish formed

RESULTS
- no schooling in response to food or plain water (control)
- formed largest school possible (10 fish in tank) when predation risk was high
- decreased school size when the smell of food also present –> a tradeoff

Question 20

social defenses:

Answer 20

• the “dilution effect” or safety in numbers alone
• the confusion effect –> fish schools confuse predators
• vigilance effect –> early detection of predators reduces effect

Question 21

vigilance effect in pigeons

Answer 21

• % of successful attacks decreased with the flock size
• response distance increased with flock size

Question 22

social defenses: mobbing behavior

Answer 22

• is when many individuals harass the predator at once

Question 23

mobbing owl predators

Answer 23

Do owls move away when mobbed? Does mobbing do any good?

• owls moved during 20% of mobbing events
• predation on moving species was 10 times lower than non-mobbing species