Flashcards in THEME 1 Deck (48):
What does behavioural ecology aim to assess?
the effects of evolutionary and environmental factors on animal behaviour
What is behavioural ecology?
1) The influence of Natural Selection on behaviour.
2) An animals struggles to survive and reproduce by exploiting and competing for resources, avoiding predators, selecting mates and caring for offspring
3) how animal societies reflect both cooperation and conflict among individuals
What are Tinbergen's 4 whys?
1) Ontogeny (development) - developmental explanations for changes in individuals (e.g. cognition and imprinting)
2) Ultimate (evolutionary) Why a species evolved the adaptions it has
3) Mechanism (causation) - mechanistic explanations for an organisms' behaviour (hormones, nerves, genes)
4) Phylogeny (evolution) - the history of the evolution of behavioural changes in a species over many generations (e.g. parental care)
Give an examples of Tinbergen's 4 whys in starlings
Learnt from parents and neighbours
To attract mates for breeding
Internal and external factors: increasing day length triggers changes in hormonal levels in the body, or the way air flows through the syrinx and sets up membrane vibrations
Song evolution – simple sounds in primitive birds, complex songs in starlings evolved
Why do female goats have horns?
- Unwanted advances from males
- Protect and kid and food from other females
- Protection from wind animals in the open (forest bovid don’t seem to have them)
Give 3 ways proximity loggers record behaviour and physiology
- Broadcast unique ID & ‘listen’ for other Ids
- Frequency and duration of ‘contacts’ logged
- Data download at recapture
Is there evidence for individual selection?
Individual magpies lay the clutch size that produces most you for them: a function of territory quality. Adapting to resources available
How do phenotype and genotype both get effected by natural selection, and how do they relate to one another in terms of passing fitness onto future generations?
It is the phenotypes of individuals that, by interacting with the environment, are subject to natural selection (selection pressures)
But a phenotype lasts one generation; it is not inherited.
It is the individual genes (and not an organism’s whole genome) responsible for particular aspects of the phenotype being passed into the next generations with varying frequency, depending on the result of natural selection
Individuals are vehicles; genes are replicators
What did Tinbergen study?
Tinbergen is credited with being one of the founders of the field of behavioural ecology
Examines the adaptive significance of behaviour, or how behaviour may increase survival and reproduction.
Give the modern version of Tinbergen's questions
Motivation – Proximate/immediate causation
Development – in the individual
Function – What problem does it solve?
Evolution – Ultimate causation
Describe how the ground finch on Daphne Major island, show the evolution of behaviour and natural selection?
E.g. Daphne Major island – Galapagos – medium ground finch
Variable beak sizes
Small bills are better at small seeds and big is big seeds
But in 1985 there was a drought – only small seeds were produced
Therefore natural selection for small billed birds
What was found that in just one year there was a sudden change in the populations average beak size
Describe how speciation could occur in finches on Daphne Island
New finch that was bigger and different song ‘named big bird’ suggested come from other island
Hybrid, could potentially mate with the resident birds but didn’t – females weren’t selecting them because not the right song
How do you measure/investigate the fitness consequences of a behaviour? And how do you measure/investigate the ‘function’ of a behaviour?
Behavioural ecologists seldom do this directly – interns of long term fitness – usually investigate at a functional level. You measure the function of behaviour by:
- Comparative studies
- Experimental manipulation
What is Optimization prediction
behaviour maximises fitness
e.g. Gazelle will visit waterhole x times per day
What is the Optimization criterion
maximum net benefit = max(b-c)
Give the benefits and costs of foraging
Foraging (= searching + handling food)
Benefit = energy intake
Cost = energy used in finding & handling food items
What are allocation costs and opportunity costs?
allocation costs = energy/time (usable for other things)
opportunity costs = cost of not performing other behaviours
What are Darwin's 5 points?
Variation: Individuals within a species differ in their morphology, physiology and behaviour
Heritable: some of this variation is heritable and on average, offspring resemble their parents more than other individuals in the population
Competition: number of offspring produced and number of individuals with successful breeding doesn’t match; population number tends to stay the same – due to competition
Adaption: as a result of competition only the fittest breed – best at gaining resources. This ability is passed on, and through NS over generations adaptions occur
Evolutionary change: in the environment changes then other variants would do best, and therefore NS occurs
If natural selection only works genetically how do behaviours evolve? What considerations should you keep in mind?
- Might still be or have been behavioural alternative
- Differences must be of have been heritable
- Some must have given greater reproductive success than others
- The link between molecular genetics and behaviours is complicated
- The link works both ways, behaviour can effect gene expression
- Genes can be shown to influence behaviour, but might not produce it
Give an example of how the same gene can give 2 different responses in 2 different animals
Drosophila vs. Honey Bees
2 morphs – sitters and rovers
forR: go foraging much further for food and can take advantage of other food patches, thrive on patchy food and high larval density
forS: sit in the same patch, thrive on evenly spaced uniform food resource
Different alleles of one gene determines this. The percentages: 30% S, 70% R, found in Toronto. Morphs are maintained due to competition being highest within morphs
I.e. a sitter does best surrounded by rovers and the other way around
The same ‘for’ gene dictates change in job in worker honeybees
Swapping from sorting honey inside the hive (sitting) or finding nectar (roving)
What did V.C Wynne-Edwards suggest about grouping of species?
If a population over exploited a resource they’d go extinct, so adaptions have come about to ensure the group or species controls it rate of consumption
That they control their breeding rate to prevent over population; producing less young or delaying breeding
Describe the example experiment on Great Tits in Oxford that proves is V.C Wynne Edwards wrong
Nest in boxes and lay 1 clutch ion the spring
Adults and young all ringed
Eggs of each breeding pair are counted (most 8-9 a year)
Young are weighed and their survival is recorded
Incubation ability isn’t the factor, as adding eggs they can still look after them
Once hatched it is the feeding that is the problem
Over a certain size they can’t do it well
Chicks will get less food less often and be smaller when they leave the nest, lighter chicks don’t survive as well
Through experiments there was an optimum number of eggs found to maximize young survival (from a selfish individuals point of view)
The most commonly seen clutch size in birds is seen close to the optimum, but slightly lower…. Why? Give 2 hypotheses
1. If brood size effects adult survival it is expected that the brood size that would give the adult greatest reproductive output would be lower than the largest one they could produce for just that season
2. Great tits if given more eggs can rear them, but we have ignored the egg production and incubation energy. A fairer test would to be somehow manipulate the birds into laying more eggs, rather than giving eggs
Both hypotheses involve measure trade-offs:
• Adult reproduction and adult survival trade off
• Trade-off between investment in egg production and incubation vs. chick care
What is phenotypic plasticity?
The ability of a single genotype to alter its phenotype in response to environmental conditions (adaptability)
Give an example of phenotypic plasticity in great tits
Songbirds breeding earlier because of climate change
• UK great tits – plastic – Have altered their breeding time since the 1970s by about 2 weeks due to caterpillar emergence
• Netherlands great tits – experienced similar to UK birds, but no change seen. Causes reproductive unsuccessfulness. (Plasticity is heritable so NS should be occurring here)
Why do hole nesting birds and ground nesting birds have different behaviours
Hole nesters vs. ground nesters
Have different behaviours all due to reproductive nest location:
Camouflaged eggs, warning predator calls, once hatched chicks hide in vegetation, mother chick calls
No need for all of the above. Hole nesters have larger clutches because
Why do male lions do infanticide when they take over a pride?
Males kill cubs after take over = Infanticide
Killing cubs brings the females back into repro, therefore:
- Can produce his own offspring faster
- Males repro lifetime is short, so a male that practices infanticide gets more cubs, therefore this trait is passed on more than the trait of not using infanticide
Describe the components of a lion pride
Lions pride consist of 3-12 adult females, 1-6 adult males and several cubs
All females stay to breed and stay with pride, but young males leave around the age of 3, and after a few years try and take a new pride from a weaker male.
Female lions in a pride are in sync with each others reproductive cycle so they all breed at once, why?
Female lions are in sync, which is advantageous because:
- cubs born together survive better due to communal suckling,
- males will have similar ages companions to leave the pride with and therefore more likely to take over a new pride successfully
What are the 3 ways to test behaviour?
1. Comparisons between individuals in a species: success may vary between individuals
2. Experiments – can vary one factor at a time,
3. Comparison amongst species – different pressures and needs give information onto why different things effect different animals
Give 4 downfalls to the comparative method
1. Alternative hypotheses
The explanations given are certainly plausible but other hypotheses haven't been rigorously examined too
2. Quantification of ecological
the ecological variables haven't been counted, for example for weaver birds, are the seed patchy and food dispersed?
3. Cause and effort
E.g. weaver fish with a diet of seeds go around in flocks. Our explanation was seed eating selects for flocking as its best for finding patchy food. But it could easily be predation selects for flocking and seed eating is forced as it is an abundant food source
4. Alternative adaptive peaks and none-adaptive differences
Tempting to assume differences are always adaptations, but easily could be alternative solutions to the same pressures
What 3 improvements to the comparative method did Clutton-Brock and Harvey make when studying primate social arrangement?
1. they measured behaviour and morphology on a continuous scale rather than categories
2. they considered alternative hypotheses, and used multivariate stats to see different ecological variables of each trait
3.Used different genera as independent data points for analysis, rather than species to reduce the problem of similarity through common ancestry
How would the home range of insectivores or Frugivores vary from leaf eating primates of the same size?
Insectivores and Frugivores are specialist feeders and their food isn't as common or abundant as leaf eaters.
Therefore, their home ranges are larger as their food is more dispersed
What are the 2 hypotheses for sexual dimorphism in body weight in primates?
1. Could enable males and females to have different food niches – avoid competition
(BUT If this were true, dimorphism would be greatest in monogamous species)
2. Could have evolved through sexual selection; males large because it means they can get more females (Supported by the comparative body weight)
What are the 2 hypotheses for sexual dimorphism in tooth size in primates?
Males have larger teeth: 2 hypotheses
1. Defence of group against predators
2. Competition with other males
- the problem with this as body weight is a confounding variable, tooth size could just reflect body size
- sexual selection theory is supported for evolution of large teeth in males, nevertheless we can’t exclude predator defence, because maybe the harem forming animals are the ones at risk from predators
Conclusion: both have influenced evolution of tooth size. Also differences in tooth size could prevent food overlap and competition
Even with careful analysis it may be difficult to tease to the effect of multiple variables on evolution
Why do male chimpanzees have smaller testes than male gorillas and orang-utans
The heaviest primates are the gorilla and orang-utan have breeding systems that involve one male monopolizing mating with several females, and have testes that weigh between 30-35g respectively
Smaller primates such as chimpanzees have a breeding system of multiple males copulating with each oestrous female, and testes weighing 120g
It would be logical that the gorillas who only need to ejaculate enough to fertilize the females have smaller balls than the chimps, as the chimp’s sperm has to compete with other sperm and therefore increased production is favoured
Describe the experiment and outcomes of Tinbergen's observations of black headed gulls on sand dunes
Parent gulls were seen picking up and removing egg shells from nest. This is crucial to survival of chicks as the insides of the egg are white and very conspicuous (the parents and chicks themselves are well camouflaged)
Tinbergen carried out an experiment:
- Painted hens eggs like the gulls eggs, then put white broken eggs next to them.
This confirmed that the eggs are targeted much more when shells are near them
However , the parents only remove the shell 1 or 2 hours after the breaking. The delay is due to the risk of leaving a newly hatched chick – wet down is easily swallowed by neighbours, so they wait until chick is dry
This is a trade-off between camouflage and chick care
Give a comparison bird to the behaviour of the black headed gulls observed by Tinbergen
In comparison an oystercatcher who also nest in the dunes. also needs to remove the shell but doesn’t have the threat of cannibalism as it nests alone, therefore removes the shell almost straight away
What is the goal of an optimality model?
an optimality model seeks to predict which particular trade-off between costs and benefits will give the maximum net benefit to the individual
What are Incidental groups and Social groups
Incidental groups: in a common place e.g. using a common food resource or water or roost site
- reflect intrinsic sociability
- common fish, birds and mammals
- vary in sixe, permanence, and function
-may be single or multiple species
What is local enhancement?
The process by which an individual's attention is directed to the location of food by other group members
i.e., learning what to eat or where to eat by observing others.
E.g. family group, or partner finding food and showing and teaching young
Give an example of local enhancement
Great Tits (Parus major)
Kept in aviaries with artificial 'trees', where at the end of each 'branch' was a container (N = 60) where birds could search for concealed food
Recorded amount of food found by each bird in a fixed time period
Tested birds alone, in pairs, in flocks of 4
% of birds finding food/15 min period:
single bird = 25%
two birds = 40%
four birds = 75%
Conclusion = Local Enhancement
Describe how foraging in a flock can get a subordinate bird less food but it is still an advantage to be in a flock?
Dominant birds usually obtained more food than when alone; degree of advantage increased with rank (dominant birds took over lower-ranking birds that found food)
Lowest ranking birds obtained about same or slightly less food than when alone
Probability of flock finding no food = 20%
Probability of subordinate finding no food = 58%
So why join a flock?
Dominant individuals benefit by obtaining more food, and subordinates benefit by a reduced probability of getting no food at all (risk-minimization)
What is meant by a group acting as an information centre?
Groups or colonies may be advantageous if individuals share information about the location of ephemeral patches of food
Give an example of a group acting as an information centre
Juvenile raven roost on Anglesey
Birds seen to go off separately and feed in the day but lots come back to a communal roost
- Sheep, hare & squirrel carcasses 2-30km from roost baited with coloured beads; carcass eaten could be told from droppings
- Beads from the same carcass found in pellets appear in same part of roost
- Number of birds leaving roost and arriving at carcass increase together over 5 days – animals are learning from an individual that there’s food in a certain location. Flight direction matched carcass bait.
Conclude: same birds leaving & arriving, and evidence for recruitment from a single bird :
- The same bird (not necessarily the recruiter)
- Gave pre-roost evening displays
- Initiated morning departures, with vocalizations
- Was first at carcass
- Appeared dominant to others at carcass
Give 3 downsides to foraging in a group
1. Subordinates may not get food
2. Search time: benefit of reduced search time reaches asymptote quickly as group size increases.
- In large groups individuals may interfere with each other
- individual search areas may overlap
- more individuals may increase the evasive action of pre
3. Energy needs:
- energy (i.e., food) available is limited
- energy needs continue to increase with increasing group size
- As group size increases, energy needs will exceed availability
Why might a group be more vulnerable to predators once they reach a certain size?
If groups get too large, individuals may actually be more vulnerable to predators.
Crisler (1956) - Wolves captured caribou in very large herds more easily than caribou in smaller herds; caribou in large herds may not be able to see approaching wolves.