Behavioural Ecology

Question 0

‘Ingredients’ of a model

Answer 0

Choices eg possible copulation duration
Constraints eg search time
Currency eg long term rate of fertilising eggs

Question 1

Explain the ideal free theory

Answer 1

Predicts the distribution of animals competing for resources distributed in patches.
Number of individuals that aggregate in patches is proportional to resources on the patch.
Ideal - animals are aware of quality of each patch.
Free - animals are free to move.
If too many predators are in high quality patch it pays to move to smaller patch.
At equilibrium all patches filled to proportion, all competitors do equally well, and no one gains by moving.
Minimises resource competition and maximises fitness.
Stable distribution is when r1/n1=r2/n2.

Question 2

Explain the marginal value theorem

Answer 2

Optimal point to move on (from a patch in which animal is foraging/ to stop copulating and find new mate etc) is when the instantaneous rate of gain drops to the overall rate of gain - tangent to gain curve on graph.

Question 3

Prey choice in Great tit (Parus major) Experiment

Answer 3

Krebs et al. (1977)
Mealworms on a conveyor belt
Tend to specialise in type 1 (best prey) when it’s best to do so
However not all-or-none - “partial preferences”

Question 4

Copulation in dung flies - model

Question 5

Explain The Handicap Principle

Answer 5

A good genes theory
Amotz Zahavi (1975)

• The male ornament is a handicap
• costly to produce and/or detrimental to survival
• Only high quality males can afford the cost of producing/maintaining the handicap
• The cost ensures the ornament is a cheat-proof signal of quality - shows females he is the best as he can withstand handicap
• Attractiveness itself unimportant to females
• handicap is not a paradox

Question 6

Problems with the handicap principle and solutions

Answer 6

Problems proposed by Maynard Smith (& others) in the 70’s/80’s
Problem 1:
Males pass on the handicap as well as the ‘good genes’
Disappears if handicap is strategic and if cost to low quality males is higher than for high quality males (Grafen 1990) - cost is relative
Problem 2:
If the ‘good genes’ are so good, they will spread rapidly to fixation (everyone has them) - what is the use of being picky?
Disappears if there are other forces maintaining genetic diversity.

Question 7

Define communication, signals and cues

Answer 7

Communication
Process in which signallers use particular traits to transfer information and modify the actions of receivers

Signals
Traits that have evolved to influence the behaviour of other individuals

Cues
Traits that provide others with information unintentionally

Question 8

Example of a signal

Answer 8

dewlaps (in Anolis lizards) are used by males to help in the defence of their territories.

Question 9

Example of resource-defence polygyny

Answer 9

Orange rumped honey guide:

• males defend bees’ nests
• females come to eat beeswax
• Males obtain matings from females attracted by food resource

Question 10

Definition of monogamy, polygamy, polyandry, polygyny and promiscuity

Answer 10

Monogamy: each individual only has 1 mate
Polygamy: individual has multiple mates
Polyandry: 1 female has multiple male mates
Polygyny: 1 male has multiple female mates
Promiscuity: both sexes have several mates

Question 11

Defending mates and spacial distribution

Answer 11

Spatial distribution matters.
If females are dispersed then it will be hard for a male to monopolise more than one female -Monogamy favoured.
If females are clumped then some males may be able to monopolise several females - Polygyny favoured.