Lecture 18-22: Barber Flashcards
What is the comparative approach to behavioural ecology?
Similarities between animals due to native environment, then map this to phylogeny. - Ecological factors make a large difference
How are mathematical models used in behavioural ecology?
Analysing trade-offs (cost-benefit analysis) Works on the assumptions that the current generation is the offspring of the individuals in the previous generation who made the correct decisions.
Explain the basis behind kin selection and inclusive fitness:
Helping others which are related to you increases your future fitness despite possibly decrease the individuals in the present moment. Inclusive fitness: success of all genes you share with others which will be transmitted to future generations
What serengeti lion behaviours have been studied in behvaioural ecology?
Females entering oestrus at the same time Low birth rate All young killed by new males in a group
What was discovered about female lions entering oestrus at the same time?
Caused by pheromones –> synchronisation Functional benefit: synchronous cubs (brothers) which leads to increased survival, synchronous suckling
What was discovered about the low birth rate in female lions?
Caused by the fact there is a discrete period of ovulation. Functional purpose: increases paternity uncertainty, therefore reducing competition - best sperm will win
What was discovered about why new males kill all the young?
Functional: females come into oestrus faster without cubs, previous cubs would create competition for new cubs Causal: males kill cubs, hormonal change in females leads to abortion.
What evidence is there for a genetic component to behaviour?
Genetic mutants: radiation and chemicals causes different behavioural mutants Artificial selection: able to select for behavioural traits which then leads to more extreme results in the next generation. Different populations have genetic differences –> differences in behaviour.
What examples are there of different behaviours in different populations of the same species.
Garter snakes prey preferences depending on location (differences in food availability) shown by presence of slugs in diet Migratory behaviour of blackcaps (all german birds migrate, 20% english, no cape-verde birds), hybrid of german and cape verde birds –> 60% migratory (dominant gene)
What is the unit of natural selection?
Genes -create phenotypes which can be selected on
Please explain the modern darwinian theory?
- Organisms have genes which code for protein synthesis 2. These proteins regulate development and therefore influence behaviour 3. Many genes exist in different forms (alleles) which code for slightly different outputs 4. The different alleles lead to differences in behaviour and therefore variation 5. Any allele which makes more surviving copies of itself will eventually become fixed in the population 6. Natural selection is the differential survival of alternative alleles.
How are economic decisions made in animals?
The best achievable balance of costs and benefits - optimal behaviour –> most offspring - sub-optimal behaviour –> decreased levels of offspring
What are the key concepts behind economic decision making?
All behaviour takes time and costs energy which cannot be re-allocated. Multi-tasking causes a loss of efficiency
How does corvid foraging strategies demonstrate economic decision making?
Have to drop each shell-fish repeatedly from a height to open them. 15% of drops are made at the peak 85% of drops are made just after (see where it lands) Want to use the minimum possible energy.
How can you analyse optimal foraging?
Analyse actions in the view of future reproductive success (FRS) Could use net rate of energetic energy (gamma) Foraging efficiency = energy gained / handling time Starvation / predation avoidance
How can net rate of energetic gain be used to analyse optimal foraging?
Try to maximise energy gained from time spent foraging. Try to minimise time spent acquiring energy Energy gained - energy used= gamma
What species feed differently depending on the cost-benefit analysis?
Kestrels: either flight hunting or perch hunting - Flight hunting used in winter because despite increased cost there are huge increases in gain - Perch hunting used when food more available.
How can starvation / predation avoidance be used to analyse optimal foraging?
Risk of predation for increased quality food. Juncos in winter either get garunteed poor quality food and will starve or risk becoming prey in order to get better quality food.
What does optimal foraging depend on?
Best option depends on handling time, cost, appetite, gape limitations.
How do redshanks know which prey to chose?
Sometimes feed only on large worms, sometimes feed on both- depends on prey availability. - Short worms rejected when large worms are common. Big worms always taken.
How can you use algebra to analyse which prey a redshank should choose?
Large prey (1) are more profitable than small prey (2) Energy gained (1)/ handing (1) > Energy gained (2) / handling (2) Small prey should be taken when energy gained exceeds the energy gained from rejected it and searching for a large one. E2/H2 > E1/S1 + H2 (increased earch = less profit
What are the assumptions of the model for redshank foraging?
Should either specialise on most profitable item or eat prey as they come - no partial preferences. Will pick the correct prey because theyre the offspring of successful parents.
How can a conveyor belt be used to test partial preferences?
Large meal worms which are twice as profitable as smaller Change the encounter rate of large worms and then map the switch point Observe partial preferences.
What is the marginal value theorem?
Used to determine how long individuals should persevere when experiencing diminishing return for increased handling time
What species are used to test marginal value theorem?
Starlings and Leatherjackets - tradeoff between protecting chicks and foraging for them - limited by the amount of food they can carry (rate of fill decreases with filling)
How many prey items should be loaded before returning when diminishing return occurs?
Insert diagram Gain curve diminishes with increased beak load - When the line touches the gain curve = maximum
How does the amount of prey items taken depend on habitat quality?
Diagram Higher the quality- more time which should be spent searching
How does the amount of prey taken depend on travel time?
Diagram Further they have to travel = more searching time needs to be done (load needs to be bigger) to make it worth it. Decreased travelling time = spend less time searching
How can you manipulate optimal foraging with a feeder?
Experimental data fits what is predicted
How are reproductive decisions made in dungflies?
Males compete for females on cowpats When more than 1 male mates with a female, the final male fertilises about 80% of eggs- depending on copulation time (males can be dislodged) Increased time copulating –> increased fertilisation
When should male dungflies leave a female to find another mate?
Copulate for 100s = 100% fertilisation, 40s= 90% Time spent copulating depends on the female availability.
What resources are competed for?
Food, space (territory, nests), mates, scare materials (nutrients)
What are the types of competition?
Interference or Resource defence
Describe the different types of interference competitions?
Exploitation: resources already removed by other competitors Scramble: intereferences over each resource item, faster responder wins, no aggression just jostling for position Contest: aggressive interaction over each resource, winner has the opportunity for excluding items and defending –> Resource defence
How can starlings demonstrate competition?
Single bird in a habitat –> no interference Two birds in a dispersed patch –> no serious interference ( food still plentiful) Two birds in a clumped habitat –> some interference Many birds in a clumped habitat –> increased interference - one dominant bird can exclude resource availability.
How is the amount of interference proportional to resource distribution?
Clumped resources –> increased encounters due to increased density of competitors (>1 competitor decides to go for the same item –> aggression)
How do brown hares demonstrate competition?
Aggregate in groups for feeding –> improved vigilance With increased group size there is also increased aggression Insert diagram
How does IFD change with individuals?
Individual reward diminishes with increased number of competitors Rich habitat will fill up faster, because an equal number of competitors –> more reward Some animals move to a poorer environment which is less exploited. Insert diagram.
How can gall aphids demonstrate unequal competition?
Large leaf stems can support 7x as many eggs as a small leaf. Larger leaves are occupied first. Next competitor will have choice between singular occupation on a small leaf or co-occupying larger leaves. - Will share with 1 or 2 = still beneficial -Reproductive success decreases with decreasing density, but increases with increasing habitat quality. Insert diagram
What is despotic distribution?
Territories form in high quality environments when aggressive guarding of resources occurs. - territories fill until no more competitors can enter (A) - competitors go to lower quality territories –> fill up (B) Any further competitors may just float (no territory) Insert diagram
How does the distribution of competitors change under monopolised resource conditions?
Monopoliser reaps benefits, but must spend energy protecting resources (territory guarding, fighting). If costs outweigh benefits then resource should not be defended, but it should be if benefit outweighs costs. This also depends on habitat quality.
Does this depend on the environment.
Some environments require an exponential cost to defend resources e.g. walking perimeter Some environments the costs are less / increase in a linear manner.
How does the predation sequence work?
The predator and prey must overlap temporally and spatially. There are a number of paths with predators and prey which can lead to escape, death, consumption Must pass through a series of stages shown in the picture
What is the probability of the predation sequence occurring in each different path?
Anti-predator behaviour can develop at any level.
How are moths used as an example of crypsis, specifically disruption camouflage.
Pinned artifical moths (with a meal worm) of varying patterns to trees and then monitored the survival Disruptive > Camouflage > Solid
What depends on how the well the cuckoos mimic the colours of the host eggs?
Depends on discrimination ability and different gentes (host specialisism) –> dunnocks do not discriminate so cuckoos dont bother –> meadow pips do discriminate –> cuckoos mimic eggs A product of co-evolution - Host species learn to remove odd eggs - New hosts (dunnocks) or those species which have never been hosts have not evolved this ability.
How does possible cuckoo hosts change with co-evolution and rejection of eggs?
Birds with higher rejection rates are likely to have been previous hosts. Hosts which are moving towards the right of the graph will eventually be used less. Select for hosts with less rejection –> adaptation in this species Old hosts may eventually lose adaptation if not used by cuckoos for a while –> possible host again.
How is risk dilution and safety in numbers, a benefit of grouping
predator avoidance ——> clumped prey maybe harder for predator to locate ——> decreased probability of an individual entering a predators detection zone
How is attack dilution a benefit of grouping?
Predators can only catch a limited amount of prey - lions will only catch one wildebeest Per capita risk is decreased: individual risk = 1/ number of individuals Also harder to attack a group than an individual - Some predators do however specialise on hunting groups (humpback whales, killer whales, humans)
How is predator confusion a benefit of grouping?
Attack success on larger groups decreases faster than 1/N Aggergated prey move synchronously to overwhelm the sensory ability of predators. Most effective when the prey all looks and acts the same Increasing school size –> decreased capture
What other benefits are produced from increased group size?
Increased detection distance Communal defence: mobbing, radial protection (elephants), radial protection (mongoose), increased numbers = increased protection
What are the overall affects of all anti-predator benefits on predator prey interactions?
Why do individuals recruit others to a foraging area?
If group benefits outweigh costs then the individuals will actively recruit other members to the foraging site. It does however depend on how divisible the resource (food) is- slice of bread is harder to share than crumbs.
This is shown by chirrup rate
Do all individuals benefit equally?
If an individual stands out it is far easier targeted by predators. Extremes of a population will stand out more –> more likely to be predated.
Are all members of a group equally protected?
Protection depends on position- selfish herd theory Proven by the shoaling fish experiment
