Chapter 6: Antipredator Behavior and Foraging

Question 1

two approaches to escaping predation

Answer 1

1) do it alone 2) social defense

Question 2

Why do harvester ants mate in groups?

Answer 2

Harvester ants form huge but brief mating aggregations on hilltops. The dragonfly eating an ant cannot possibly eat them all. Social defense against predators.

Question 3

explain social defense in chironomids

Answer 3

Male chironomids form swarms at dusk. Females fly into the swarm and copulation occurs on the wing. Females are less likely to be eaten if they are surrounded by other flies

Question 4

Dilution effect hypothesis for social defense

Answer 4

associating in groups will make it less likely that any one individual will be predated

Question 5

confusion effect hypothesis for social defense

Answer 5

moving as a group may reduce the likeligood of predators capturing prey because of their inability to single out and attack individual prey

Question 6

the selfish herd hypothesis for social defense.

Answer 6

individuals in a group (or herd) attempt to reduce their predation risk by putting other individuals between themselves and the predator.

Question 7

explain the dilution effect in butterfly groups

Answer 7

butterflies drink from large brazilian mud puddles. Individual butterflies that “puddle” in large groups experience a lower risk of daily predation than those that suck up fluids from the ground by themselves or in small groups.

Question 8

two ways that solitary organisms blend in with their environment

Answer 8

1) evolving camouflaged color patterns 2) behavioral tactics.

Question 9

Explain moth backgroun selection and color morphs

Answer 9

Specimens of typical and melanic peppered moths were attached to tree trunks or limb joints in POLLUTED and UNPOLLUTED woodlands. Moths of both types were less likely to be found by bird predators when sitting on limb joints: melanic (BLACK) moths did better in POLLUTED woodlands – typical (WHITE) moths did better in unpolluted woodlands.

Question 10

how can standing out be a predator defense rather than camoflague?

Answer 10

standing out may act as a warning

Question 11

aposematic colouration

Answer 11

warning colouration is often used by noxious organisms to signal their UNPALATIBILITY to predators

Question 12

explain the aposematic coloration of monarch butterflies

Answer 12

Monarch butterflies that feed on toxic milkweeds as caterpillars store the cardiac glycosides in their bodies and wings when they become adults. they are brightly orange colored

Question 13

Explain the aposematic coloration of blister beetles

Answer 13

Blister beetles, which have blood laced with CANTHARIDIN, a highly noxious chemical, often mate conspicuously for hours on flowering plants.

Question 14

WHAT IS BATESIAN MIMICRY

Answer 14

Not all animals with aposematic colours are noxious: when an EDIBLE species resembles a TOXIC or dangerous one, it is called Batesian mimicry

Question 15

EXAMPLE OF BATESIAN MIMICRY

Answer 15

A tephritid fly waves its legs to mimic a jumping spider, the threat display of the spider. Doing so deters attack from the spider.

Question 16

signal deception hypothesis

Answer 16

when a prey’s appearance of behavior activates escape behavior on the part of the PREDATOR. (The behaviour of the tephritid fly appears to deceive a potential predator, the spider actually runs away from the fly because he thinks the fly is a threat rather than a snack)

Question 17

antiambush hypothesis

Answer 17

when animals sacrifice speed or other adaptive escape mechanisms to scan ahead for other as-yet-unseen enemies ex/ gazelles stot, they jump really high in the air, but its not as fast as sprinting. they can see lions in the grass ahead.

Question 18

4 hypotheses as to why gazelles may stot:

Answer 18

1) ALARM SIGNAL HYPOTHESIS: gazelles stot to communicate predation risk to conspecifics 2) CONFUSION EFFECT HYPOTHESIS: if several gazelles stot simultaneously in a group while fleeing, then the predator may become confused 3) SOCIAL COHESION HYPOTHESIS: gazelles stot to attract conspecifics to join them 4) ATTACK DETERRENCE HYPOTHESIS: gazelles stot to signal their vigor to potential predators

Question 19

In order for stotting to be an honest form of communicatoin, both the sender (gazelle) and receiver (cheetah) must ___

Answer 19

BENEFIT. if it is an honest signal, then it would pay for a cheetah to call off the attack to avoid wasting time and energy

Question 20

How do lizards “honestly signal” to their snake predators?

Answer 20

The time an individual spent running until exhaustion was positively correlated with the number of push-ups it performed under a perceived threat from a model snake. the lizard thus does pushups to indicate that it will be “hard to catch,” and the snake doesn’t waste its time

Question 21

____ ____ is a tool used by animal behaviorists to perform a cost-benefit analysis.

Answer 21

OPTIMALITY THEORY

Question 22

what is optimality theory

Answer 22

the notion that adaptations have greater benefit to cost ratios than the putative alternatives that have been replaced by natural selection.

Question 23

Natural selection should favour adaptations with greater ___ ___ ___ ratios

Answer 23

Natural selection should favour adaptations with greater BENEFIT TO COST ratios

Question 24

DRAW A GRAPH OF THE OPTIMALITY MODEL

Answer 24

Question 25

Outline the optimal covey size for the northern bobwhite quail

Answer 25

Northern bobwhite quail spend the winter months in small groups, coveys, which range in size from 2 to 22 individuals

Bobwhite in larger coveys likely gain an antipredator benefit; they don’t have to perform as much antipredator vigilance

But living in a larger group elevates costs of competition for food

Field studies show that daily survival rate for an individual is highest in groups of 11

Question 26

___ is the currency used in most optimal foraging models, and e____ ___ ___ ____ (time or energy spent searching or handling) is what is being optimized.

Answer 26

Energy is the currency used in most optimal foraging models, and energy gain per cost (time or energy spent searching or handling) is what is being optimized.

Question 27

theory htat predicts about how animals maximize fitness while foraging

Answer 27

optimal foraging theory

Question 28

marginal value theorem

Answer 28

part of the optimality model: predicts than an animal should leave a patch when its rate of food intake in that patch drops below the average rate for the habitat, and that this marginal capture rate should be equalized over all patches within a habitat.

Animals must decide when to leave one food patch and search for another, more profitable one.

Question 29

explain central place foraging in ospreys

Answer 29

Ospreys catch fish in the marsh below and return them to their nest to feed chicks. We expect foraging ospreys to be selective about the prey they return to nests. Rather than moving, like in the marginal value theorem, they stay where they are but the venture different places to forage, bringing food back with them.

Question 30

Explain the optimal foraging decisions of northwestern crows

Answer 30

Northwestern crows forage on the beach for whelks (a marine snail) with thick shells. The crows drop whelks to break the shells. Reto Zach studied the relationship between height, snail size, and the number of drops to break the shell.

The crows take only large whelks and fly up 5 m to drop them:

For a large whelk, the energy gain was 2 kcal, and the flight cost was 0.5 kcal for a net gain of 1.5 kcal

For a medium whelk, the crows needed many more drops, and the net energy gain was actually a loss of 0.3 kcal

The crows rejection of ALL BUT LARGE whelks was adaptive

Question 31

Why don’t oystercatcher shorebirds choose the largest mussels?

Answer 31

even though largest muscles contain the most energy, it isn’t profitable because it takes so much energy to crack the mussel, or you need to abandon the mussel completely.

they prefer intermediately sized mussels because you get more food energy for the energy expended.

Question 32

why is energy maximization of the optimal foraging theory not always the best policy?

Answer 32

there may be unaccounted dangers of trying to eat food sources with too much energy (ex/ hard to catch, dangerous to hunt).

ex/ large Catfish have locking spines and are dangerous to swallow. A garter snake that tried to swallow a small catfish. The snake survived. It took many days to digest the catfish and eventually the spines fell out. Wasn’t really worth it.

Question 33

If foraging exposes an animal to predators, we might expect foragers to sacrifice short-term caloric gain for long-term survival. What animal displays this sacrifice?

Answer 33

dugongs feed on sea grasses while trying not to be fed on by tiger sharks. when tiger sharks aren’t in the area, the dugongs bury their head in the sand to get the nice nutritious roots. but when sharks are in the area, they resort to cropping the most superficial blades of sea grass so they can maintain a look out for predators.

Question 34

criticism with the optimality of feeding model

Answer 34

the optimal feeding model suggests that animals will just go for the most energy-packed meal. but they fail to consider the trade-offs between foraging success and predation risk. Sometims animals will eat less nutritious food for long term survival.

Question 35

Game theory to explore the adaptive value of foraging behavior.

Answer 35

Whenever two or more foraging phenotypes exist in a population, an obvious question is why hasn’t the type associated with higher fitness replaced its rival over evolutionary time?

game theory suggests that different foraging phenotypes can coexist together due to frequency-dependent selection in which the fitness of a genotype can either increase or decrease as the genotype frequency in the population increases.

Question 36

explain game theory and feeding behavior in fruit fly rovers.

Answer 36

Fruit fly larvae exhibit two different genetically-based strategies: Rovers and Sitters

Rovers that move about four times as far as Sitters

Both types of larvae are common in some places

The two phenotypes can co-exist indefinitely due to NEGATIVE frequency-dependent Selection.

- When sitters are common, rovers do well and increase in frequency: when rovers are common, sitters do well and increase in frequency

Question 37

explain the negative frequency-dependent selection in the african cichlid fish.

Answer 37

The frequency of right and left-jawed Perissodus oscillates: when right-jawed fish predominate, their fitness goes down, and left-jawed fish increase in frequency, and vice versa.

Question 38

the ___ of ___ describes how the fear by prey of being eaten influences their foraging and movement behavior

Answer 38

LANDSCAPE OF FEAR.