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BI310 > Groups > Flashcards

Groups Flashcards

1
Q

What are the advantages of grouping?

A

Protection against predators
Improved foraging for food

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2
Q

Why do animals aggregate?

A

Due to attraction to a specific environmental factor e.g. food

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3
Q

How do groups provide protection against predators?

A
  1. Improved Vigilance
  2. Dilution
  3. Shielding
  4. Predator confusion
  5. Group defensive behaviour
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4
Q

How do animals benefit from the vigilance of others?

A

They spend more time feeding and less time watching out

The more scanners there are the quicker the response to a predator

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5
Q

An example of predators being less successful due to group vigilance

A

Goshawks are less successful attacking larger flocks of pigeons
The pigeons fly off earlier while hawk is still distant

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6
Q

Why do individuals not cheat?

A

The first animal to spot the predator has the best chance of escape

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7
Q

What is dilution?

A

The larger the group the less likely it is for an individual to be taken by a predator

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8
Q

Examples of dilution

A

Horses in larger groups are bitten less as seen in the Camargue cluster when tabanid flies are active.

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9
Q

Shielding

A

Members of a group use other members as protection - a living shield - against predators.

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10
Q

What is the result of shielding?

A

There will be a clumping of individuals, where the individuals might be safer if they agreed to spread out

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11
Q

What does the fitness payoff of an individual in selfish herding depend on?

A

It depends on what others in the group are doing

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12
Q

An example of the prediction of the selfish herd hypothesis

A

In Bluegill sunfish
- the central nesting sites are the safest
- the males compete intensely
- the central territories are won by larger fish

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13
Q

Predator confusion

A

Many prey moving about make it hard for the predator to fix on and follow any one of them.

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14
Q

How is predator confusion shown in fish?

A
  • A pike given one prey fish at a time in a tank catches more prey per unit time than when feeding on shoals of fish
  • Minnows marked with ink were more likely to be eaten in a group of minnows without the mark
    -the markings make it easier for the predator to keep an eye on them
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15
Q

An example of how predator confusion explains alarm calls

A

Ground squirrels give the alarm call, then all run to safety confusing the predator

The caller has a 10-fold lower risk of being eaten than other squirrels

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16
Q

How does Kruuk’s experiment support the hypothesis for the adaptive value of mobbing behaviour?

A

Mobbing behaviour distracts predators from the mobbers’ offspring
- Hen eggs were placed inside (protected by mobbing) and outside a gull colony
- The predators (crows) were mobbed more
- the crows were less successful in their predation attempts when targeting eggs within the colony

17
Q

Example of interspecific altruism

A

Humpback whales save other species from orca attack
- appear to protect seal by keeping it on its belly

18
Q

How is group defence shown in mammals?

A

Buffalo’s travel with their young near the centre of the herd

19
Q

How do honeybees communicate about the location of food?

A

The scouts perform a waggle dance

20
Q

What are information centres?

A

Individuals find out about the location of good feeding sites by following others

  • proposed by Ward and Zahavi
21
Q

What are the predictions of the information centre hypothesis?

A
  1. Birds should leave in groups and fly off in the same direction e.g., barn swallows
  2. Leaders of groups should be birds that were recently successful e.g., shown in cliff-nesting swallow and Osprey
22
Q

Flocking is advantageous to which species?

A

species that exploit food that is patchily distributed and unpredictable (e.g., seeds)

23
Q

What type of defence is important in predators such as lions and hyenas?

A

Cooperative carcass defence may be more important than cooperative hunting in predators such as lions and hyenas

24
Q

An example of how animals protect themselves from physical factors.

A

-Emperor penguins huddle together for warmth
-Colonial weaver birds’ nests maintain uniform temperature

25
Q

What are the disadvantages of grouping?

A
  • Increased conspicuousness to predators
  • Competition in feeding
26
Q

An example of increased conspicuousness

A

A colony of fieldfare nests attract more predators than a single nest

  • But nests also protect them from mobbing
27
Q

What are the two types of competition in feeding?

A
  1. Direct exploitation (many mouths compete for food)
  2. Interference
28
Q

Example of direct competition for food

A

Predator fish (Jack- Coho salmon) do better in a group but those at the front catch more prey than those at the back

29
Q

An example of interference between group members

A

Redshank feed on shrimps that retreat into burrows when they detect an approaching bird

30
Q

What is nearest- neighbour distance?

A

It reflects a balance between the costs (interference) and the benefits (protection) of group living

  • e.g. in knots distance is higher during the day (feed on shrimp) than at night (feed on snails)
31
Q

How does increased parasite transmission occur in cliff swallows?

A

They build nests close together and favour swallow bug transmission

32
Q

Cuckoldry and mate competition occurs in which birds?

A

In colonial-nesting red-winged blackbirds the mates of vasectomied males laid fertilised eggs by a male other than their mate

33
Q

An example of a group where cannibalism of the young occurs?

A

In bluegill sunfish a male may eat his neighbour’s eggs
- reduces benefit of group defence against predators

34
Q

An example of a group where cannibalism of the young occurs?

A

In bluegill sunfish a male may eat this neighbour’s eggs
- reduces benefit of group defence against predators

35
Q

What is the optimal group size for an individual?

A

It is the size at which
- fitness is maxismised
- time spent in vigilance and fighting combined is lowest

36
Q

What are the effects of group size on Yellow eyed Juncos?

A

As group size increases
- birds spent less time in vigilance
- spent more time fighting

37
Q

Optimal group size depends on what environmental factors?

A

-predator risk
-food availability
-cover availability

38
Q

Group size may vary depending on what activities in rooks.

A

-feeding
-nesting
-winter roosts

BI310 (7 decks)

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