Behavioural ecology Flashcards
what are Niko Tinbergen’s four “why?”s questions?
- Causation - What are the Mechanisms causing the behaviour to happen - neurobiology, gene expression - the ST mechanisms that cause the bhv. 2. Development - Ontogeny (in invididual’s life) - is bhv learnt / instinctive? The degree to which the bhv is controlled by genes or environmental. 3. Evolutionary history or Phylogeny of the bhv - do we see similar bhv in close relatives? What point in evo time did this bhv first evolve?when was the transition + what was the selective force? 4. Function - Adaptive value - what use is it to the animal in its life? How does NS favour that bhv + how does NS act on it.
How is an animal’s behaviour adapted to its ecological circumstances?
o Behaviour o Ecology o Evolution Understanding the function of behaviour requires an understanding of the ecology of the animal in question. Only by understanding the role of the behaviour in the animal’s life can one understand why the behaviour evolved and why natural selection favours it today.
why is natural selection is an optimising agent?
works as if nature was optimising fitness: only the best survive + reproduce successfully. - The optimum behaviour will depend on the costs and benefits of alternative courses of action.
what are the two types of economic model used by behavioural ecologists?
Optimisation - heavy use of economic models to understand behaviour and generate hypotheses that can be tested.: simple optimisation models, which quantify the costs and benefits associated with a behaviour and calculate the optimum trade-off between these costs and benefits, Game Theory - game theory is essential when the best thing to do depends on what other individuals are doing; (aggressive interactions etc) game theory becomes useful when analysing social behaviour.
Why do black headed gulls remove the eggs of their newly hatched chicks some 15 to 20 minutes after the chicks are born? What is the adaptive value? how did Tinbergen solve this?
- There are many possible functional explanations. For example the chicks could injure themselves on the sharp shell, or bacteria could grow on the inside of the shell and be a source of infection Experiment: hen’s eggs in artificial nests: put painted hens eggs in artificial nests, as food for predators, and placed broken shell near these artificial nests or not. Result: enough, nests with white eggshell in them had a higher predation rate. Parents remove shells only after chick dried out and fluffy
Why do male dungflies copulate as long (or as short) as they do?
There is a trade-off between the benefits of extra time increasing his paternity with this female (eggs fertilised) and time being wasted that could be better spent looking for a new female. The currency, the long-term rate of fertilising eggs, = the percentage of females egg is fertilised divided by the total time taken. The time is not simply the time is spent with the female copulating, it should also include the time searching for females.
what are the three ingredients of the Marginal value theorem?
1) Choices a. possible copulation durations 2) Constraints a. gain curve (time)) b. search time 3) Currency a. long-term rate of fertilising eggs. - not just about success with this F, success over a long period of time (mating season of dungflie) a series of choices to pick between, a set of constraints within which the animal must operate, and a currency by which success is measured.
what is the trade-off Foraging in patches?
between the gain rate within a patch (energy gain from food) at a high rate early on but slowing down with time in the patch, and the cost of travelling between patches.
what did Alex Kacelnik (1984) do?
Trained wild starlings, feeding their young in nests, to come to feeder for mealworms, where they received mealworms at a controlled rate. o This ensured that all birds experienced a specific gain curve with diminishing returns o Varied distance between feeder and nest (greater distance, greater travel time) o experimental manipulation was to move the feeder different distances from the birds nests, and record how the time spent in the patch (and the number of mealworms) changed. This kept everything under tight environmental control.
how did Krebs study Prey choice in great tits - Great tit, Parus major
Krebs varied the encounter rate of the birds with large chunks of mealworm (good prey) interspersed with small chunks (poor prey). He found that the birds were specialists when encounter rates with good prey were high (short search time) but became generalists when encounter rates were low. His experiment gave qualitative support for the optimal prey choice model, but unlike the model, the birds showed partial preferences. The model predicts you should either be a complete specialist or a complete generalist either side of the critical search time, but the birds did not show an all-or-nothing switch.
Give a summary of Prey choice?
- If find type 1, always take it 2. If find type 2 take it if: energy content of poor prey / handing time for poor prey is > than good prey. 3. Otherwise reject it; specialise on type 1
Possible reasons for a model to fail?
o Choices could be mis-specified (or wrong model) –> Animal might not be capable of behavioural choices o Missed constraints o Wrong currency –> Predicting behaviour (energy intake that is not most critical to the animal)
What do we understand under The forager’s perspective?
Animal’s view of the world isn’t the same as ours e.g. we know the lab is safe, the animal doesn’t.
What is animal’s behaviour Animal’s behaviour influenced by? (models)
Animal’s behaviour influenced by: o learning o risk sensitivity o predation (different currency)
Steve Lima Woodpecker experiment: o Empty v 24 seeds (all holes in log filled/empty) o Empty v 12 seed o Empty v 6 seeds What did he find?
24 seeds: optimum number of holes checked –> 1 12 seeds –> 3 6 seeds –> 6 o Model assumes that woodpeckers can learn the number of seeds in non-empty logs o But once they find a seed, they tend to check every hole not predicted by model the birds have some sort of rule which gets them close to the optimal solution, but they are clearly not solving the problem the way Lima did with his model. It seems reasonable that animals use ‘rules of thumb’ which approximate good solutions to problems and don’t come equipped with specific probability distributions (or learn them).
Explain risk sensitivity and give 2 risk levels?
uncertainty (variance) in reward rather than risk of death o Risk-averse: prefer less variability/uncertainty o Risk-prone: prefer more variability/uncertainty
Risk sensitivity in small bird in winter, what was found?
During the day, as it feeds and accumulates fat, if it’s doing well (in the yellow zone) it should be RISK-AVERSE: there is no point gambling because you are on-track for the right reserves by dusk and so you should play safe. However, if you’re not on track and look like having a shortfall by dusk (in the red zone), you should be RISK-PRONE. There’s no point playing safe because a steady supply of food won’t get you above the threshold by dusk - you need to gamble.
Caraco and colleagues (1990) on Yellow-eyed junco birds, Junco phaeonotus, what was found at different temperatures (low vs high) considering risk sensitivity?
Given two feeding options differing in variance, at low temperatures when the birds’ energy balance was negative, they were risk prone. When in a positive energy balance at higher temperatures, they were risk averse. Just as predicted. Switch according to their energy budget and fat reserves.
Decisions on where to feed/when to feed influenced by what?
o Value of food o Reduces risk of dying from starvation and reserves for mate attracting and territory defense o Value of life o Effected by the value of predation o Probability of predation
What if: can only get high rate of energetic gain by accepting high level of predation? What are the 2 contexts?
Trade-off: o energy vs. predation 2 contexts: o Vigilance o Habitat choice
Metcalfe & Furness (1984) - Turnstone (small wading bird), Arenaria interpres?
o Adults but not juveniles migrate o vigilance ▼ with larger flock size o individual risk is lower and more eyes looking out for danger o adult vigilance ▼ before migration o with migration, lots of fat reserves needed (50% bodyweight gained) at the expense of higher predation risk o juvenile vigilance does not change.
How does habitat choice influence the feeding behaviour in Bluegill sunfish, Lepomis macrochirus researched by Earl Werner and colleagues (1983)?
o Added predator (bass) to one half of pond o Compared feeding behaviour of small and large fish Size o Predation risk goes down as fish gets bigger o The behaviour of the sunfish depended on their body size because predation risk goes down as they get larger. With predator o Small fish feed in vegetation around edge o One third less food, 27% less growth o Predator imposes cost even if it doesn’t kill The smaller fish accept a lower feeding rate in order to lower their predation risk. Note that this is a ‘hidden cost’ of predation risk - not death, but a lower growth rate.
Experimental evidence (Locusts) by Raubenheimer & Simpson on trade-ff between nutrients
fed locusts on combinations of 5 different protein & 5 different carbohydrate levels o Locusts on low protein diet ate more to meet protein target… but got fat (because too many carbohydrates)
What are the two types of competition face by species?
- Exploitation - resource used up by others: (eating / using them: not physical interaction but an affect on success) 2. Interference - interactions with others reduce intake rate (interfer another’s ability to forage successfully) o ‘getting in the way’ o resource defence o prey disturbed
what is ideal free theory and what does it assume?
aims to Predict the distribution of animals. Assume: animals know the value of the resources and they can move freely between them Important thing about the model: Distribution is stable if no one gains by moving (no one indiv can do better my moving = stable distribution)
what is the difference between ideal free theory when animals are equal and when they are un equal
equal: n1/n2 = r1/r2. - Ratio of numbers should = rate of energy supply of two sides UNEQUAL: cw1/cw2 = r1/r2 - Now the prediction is not n1/n2 = r1/r2 as before, but that the ratio of COMPETTIVE WEIGHTS should match the ratio of rates.
what happens when animals aren’t equal?
give each competitive weights: if split up in certain ways, average rates at each side is same –> data APPEAR to fit the prediction of input matching (the ratio of fish match the ratio of rates) even though all fish aren’t equal, as Ideal Free Theory assumes.
what happens at IFD with animals with unequal abilities?
there may be several IFDs at IFD, o all animals of same type get same rate o BUT average intake rate may differ between the patches o Can have equal average rates (i.e. input matching) even though animals aren’t equal, so need to check assumptions
what is a key concept in understanding why some animals defend territories, and only do so sometimes?
ECONOMIC DEFENDIBILITY, introduced by Jerram Brown. Defending a resource has costs (Time, energy, injury), so payoff from having unique access to the resources must outweigh the cost. Brown: Be territorial if costs < benefits
how may be resources be distributed?
Space í Easier to defend if clumped: less cost. If all your resources are close together in one place, they may be easier to defend o Time í Harder to defend if clumped. Having a sudden floor of resources at one time may actually be hard to defend
When were sunbirds most territorial? (at which activity level) and why?
Sunbirds were most territorial at intermediate levels of nectar availability: . If low, not enough profit to make costs of defence worthwhile. If bountiful, no benefits to exclusive access to flowers, so not worth paying costs of territory defence.
what types of intruders into territories are there?
Sneaks: just take resources (don’t hold territories, don’t pay cost of defending) - steal food. /mates satellites: beneficial as well as costly:
what are some benefits of sharing a territory?
o Reduces feeding rate o Help with defence if there is enough food for two birds, it pays to defend a territory together because the costs of defence are shared and more than compensated for by the cost of sharing the food. With exclusive access to food - insects being washed up on the riverbank - the birds can allow depleted stretches of bank to replenish (like the sunbirds being able to allow nectar to replenish). Without exclusive use of a stretch of riverbank, you couldn’t harvest your resources prudently.
What are secondary sexual characters?
Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a species, but unlike the sex organs, are not directly part of the reproductive system. - Body size - Weaponry - Coloration - Oramentation - Display - Aggresiveness - Sexual responsiveness - Growth rates + demands on parent - Mortality rate
Give example for weaponry Secondary sexual characteristics
o Bighorn sheep (larger horns) o Gelada baboon (enlarged canines) o Stag beetle (enlarged mandibles) o Pheasant (spurs on their legs used for fighting)
Give example for coloration Secondary sexual characteristics
(mainly in the primates because of superior colorvision) o Mandrill (male bright blue&red face and bottom) o Blue bird of paradise (male bright)
Give example for sexual responsiveness Secondary sexual characteristics
o Dungfly (Males aggregate on dung patches, will leap on every female) o Turkey (only stimulus male turkey needs to try and mount the female is a head sized ball at the hight the head of a female would be at)
Give example for ormantation Secondary sexual characteristics
o Peacock (train) o Bower bird (something the animal builds, e.g. bower: ornamental structure built by male that he decorates, purely as a display arena)
Give example for Growth rates + demands on parent Secondary sexual characteristics
o In many mammals (incl. humans), male embryos grow faster than female and so place a greater demand on the mother. Milk demand by male offspring is also higher (correlates with bodysize when they grow up).
Give example for Mortality rate Secondary sexual characteristics
o Kruger & Nesse (2004) Evolutionary Psychology 2: 66-85 o Plotted is the ration of male: female mortality (1 = equal, >1 = higher in males) as a function of age, for a range of countries. Except in old age, male mortality higher, especially during peak reproductive years. o For most of our lives, males are dying at a faster rate, particularly in the peak reproductive rate. o Source of mortality is varied: often risk driving behaviour, but also sexdifference in many diseases.
Why these sex differences?
o Different selection pressures on the two sexes o Sexual selection (Darwin 1871); Darwin’s answer: such features help reproductive competition. Called this sexual selection.
What is sexual selection
Sexual selection (Darwin 1871) o Features that promote success in reproductive competition o May be deleterious to survival o Natural (viability) selection and sexual selection may act in opposition
Give 2 examples for natural and sexual selection in opposition and what does it show?
Example 1. Tungara frog males (live in Costa Rica) croak to attract females. Mike Ryan et al. o Trade-off between croaking for mates and avoiding predation (attracting bats) Example 2. Guppies (Common aquarium fish; in wild live in streams in Trinidad) - males brighter than females. John Endler noted that males in streams where predators were absent were BRIGHTER. John Endler (1980) did an experiment in artificial pools and tracked evolution of colours over several generations. Within 2 years (8generations), males significantly more conspicuous in ponds with no or non-dangerous visual predators, but less conspicuous in ponds with dangerous visual predators. Shows (i) trade-off between colours being good for attracting females but bad ‘cos they attract predators, and (ii) sexual selection can be a powerful evolutionary force leading to rapid change (when removing the restraining effects of predationa and natural selection).
What are Darwin’s 2 mechanisms in which sexual selection acts?
- Intra-sexual selection - Competition between members of one sex for access to the other sex a. Usually male:male competition 2. Inter-sexual selection: Choice of individuals of one sex by members of the opposite sex a. Usually female choice over mates rather than males
Why is inter-sexual selection this way around (female choice)?
Bob Trivers: due to differences in parental investment in offspring; the bottom line is a difference in investment in gametes (and so contribution to egg). o Males produce lots of cheap gametes o Females produce few expensive gametes o Therefore: o Males can increase fitness rapidly by mating many times. But for every successful male, there are many losers. o The cost of a ‘bad’ mating is higher for females o This explains why (usually) male competition over mating is more intense, and why females are more choosy.
What is the 1st prediction for proving Trivers theory on why inter-sexual selection this way around (female choice)? +2 case studies
Prediction 1. Where males invest a lot in offspring, one expects sex-role reversal o Gwynne (1981) - Mormon cricket o Males produce a nutrient rich spermatophore o Males are choosy about whom they mate with o After courtship, males deposit a nutrient rich package of sperm and protein for the female to pick up (she eats the nutrient sac and MAY use the sperm). Males pay a high price if they let a female take the spermatophore but DON’T use the sperm. So they’re choosy over whom they try and court. o Direct benefit to the female (direct correlation to how many eggs they can fertilize) and high cost to male for producing the spermatophore o Example 2. Pipefish are relatives of seahorses. The males accept eggs from females, fertilise them and brood them in a pouch. o Berglund + Rosenqvist o Males pipefish brood young in a pouch o Females are ornamented and compete for males o Males are choosy o As with mormon crickets, the males are investing a lot in reproduction and a good father is worth a lot to females. So females are ornamented and compete for the best males. Males, in turn, are choosey about which females they respond to.
What is the 2nd prediction for proving Trivers theory on why inter-sexual selection this way around (female choice)? +2 case studies
Prediction 2. Sexual selection should be more intense in polygynous species with low male investment Another prediction from Trivers theory: where the prize from being the top male is larger for males, sexual selection should be more intense. Harem size in primates Positive correlation: difference in body size between the sexes (sexual dimorphism) depends on the harem size. Gorillas: large harems for top silverback and males are much larger than females. Gibbons: monogamous and both sexes similar in size.
Is there sexual selection in monogamous species?
- First, there’s still variation in QUALITY. - so yes, here is still competition for the best mates 2. Second, social monogamy doesn’t mean sexual monogamy (i.e. fidelity).
In which animal can we see that social monogamy doesn’t mean sexual monogamy ?
Great tit: thought to be strictly monogamous (male and female pair and care for young, equally, together) until advent of DNA fingerprinting in the 80’s. Actually 10-15% of young NOT fathered by the social father í Extra-pair copulations. a. Often neighbour that is of higher genetic quality (mating cannot be forced in tits).
What traits were evolved for male-male competition (intra-sexual selection)?
o Body size o Weapons like teeth, antlers, horn o Aggression (INTRA-sexual selection was rapidly accepted because it’s easy to see how a trait such as large body size helps males compete/fight with each other.) o Penis morphology (damselfly’s penis is shaped like a loo-brush, with spines and bristles. This allows the male to scoop any previous male’s sperm from the female’s genital tract before injecting his own sperm) o Chastisty belts - (In acanthocephalan worms (hermaphrodite internal parasites), after mating the female’s genital opening is sealed up by the male)
Which two questions have been the focus of attention in regards to sexual selection?
- Are females really choosing between males? or are the males sorting it out via competition and the females get the winner); + 2. What benefits do they get from being choosy? (why are they choosing)
What did Malte anderson in 1982 do? What did he find?
maped out territories of male widowbirds, and randomly allocated them to four treatments (shortened taill / elongated tail / cut +reglued for control / capture + release control): results: males with elongated tails attracted more females
Why are female pied flycatches interested in males who sing more?
• Females interested in territory quality and are simply using male song as a cue – not really interested in male at all. (F listening to songs knows that where the song is coming from has good food: good for her + easy to feed the young). It is a M trait F selct on but females only use this as a cue to the quality of food.
What are cases where only indirect benefits seem to be likely?
Leks - F only get sperm: must be something genetic
What are the two things that genetic benefits mmight be releated to and why are they benefits?
Attractiveness: Attractive mate = attractive sons –> mating advantage. 2. viability: “Good genes” - male ornament is a handicap + costly to produce / detrimental to suvival so only igh quality males can afford the cost of producing / maintaining the handicap –> cost ensures ornament is a cheat proof signal of quality.
What is fisher’s run away process?
The more females there are that prefer long tails, the bigger the gain, Females who mate with long-tailed males gain, because their sons have long tails (and so are preferred), BUT, because choosy females mate with long-tailed males, their sons not only spread the tail genes, but also spread their mother’s preference genes
How does preference reach a threshold?
genetic drift, sensory bias, Fisher’s own idea (initially a lsight eaggeration signalled viability, F gained from prefering this –> mating advantage to M with it)
What are some problems with the handicap principle?
1.: males passs on handicap too, but: dissapears if handicap is strategic + if cost to low quality males is higher than for high quality 2. if good genes are good, they will spread rapidly to fixation, BUT: disappears if there are other forces maintaining genetic diversity
What can maintain the genetic variation between males (that makes female choice worthwhile)?
- ongoing recurrent deleterious mutation, host parasite coevolution.
Define ‘communication’, ‘signals’ and ‘cues’
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 (by-product)
Difference between signal and cues
Critical distinction is between signals and cues: the former have been selected over time specifically to convey information. o Footprint convey information but are not a signal (=cue) o Mouse rusting through the grass: Another example of an inadvertent cue of presence … Draws attraction of predator, but not strictly communication: If anything, selection should have acted to minimise the sounds of movement in mice, because of the predation threat (=cue). o Example of a signal: Dewlaps are used by males to help in the defence of their territories. o Anolis lizards: dewlap has evolved to convey information and is a signal o Behavioural ecologists are interested in the evolution of signals
What do animals communicate about?
- Identity: Information from what species you are, through signals about sex, dominance status, kin, group membership, etc, all the way to your individual identity. - Identity: species (Narrow-mouthed toads) - Identity: sex (Longtail knifefish) - Identity: Individual (Bottlenose dolphins) 2. Environment: Animals also convey all sorts of information about the surrounding environment. - Environment: Food (Honey bees) - Environmen: Danger (Vervet monkeys) 3. State - A third major category of information concerns the current state of an individual. - State: Hunger (Canaries) - State: Intention(Dogs) = Information about potential future actions and motivation are also available, as shown classically by domestic dogs. - State: Quality (Peafowl)
Identity: species (Narrow-mouthed toads), How do they communicate species identity?
Communicate to vocal signals: - When these two particular species are found in allopatry (that is, when each is the only species in a given area), the calls of the males have a similar pitch; frogs and toads rely heavily on vocal communication. - When the two species are found in sympatry (that is, when both are in the same area), selection has led to divergence in call pitch; if males of both species sound the same, mating errors are more likely and so individuals sounding distinct and ensuring successful matings with females of their own species would have had a selective advantage.
Identity: sex (Longtail knifefish), how do they communicate sex?
South American longtail knifefish (Sternopygus macrurus). o Many species of fish use electrical discharges to stun prey and/or to help ‘see’ their environment. Longtail knifefish also use them for communication, with males and females producing different frequencies, thus making them readily identifiable. o Males and females differ in steady-state electrical discharges (=are sexually dimorphic)
Identity: Individual (Bottlenose dolphins), how do they communicate?
Each dolphin has its own unique signature whistle; that whistle encodes individual identity independently of voice features (=almost how human name. Group members use this whistle to get attention from called individual) –> huge debate about what constitutes true individual recognition
Environment: Food (Honey bees), how do they communicate the location of the food?
One major environmental feature about which important information is conveyed is the availability and whereabouts of food. A classic example comes from the dancing of honey bees when workers return to the hive. o Returning workers dance to convey information o Marking bees to study recruiting behaviour o Waggle dance: signal gives information about direction, distance and quality of food resource o There are two types of dance given by worker honey bees. When food is nearby, they give what is called the ‘round’ dance; workers about to leave obtain information simply from the odours on the returning individual, and when leaving the nest they search for these odours and thus the food source. For food sources further afield, workers use the ‘waggle’ dance. This conveys information about the direction the food can be found (the angle of the bee dance relative to vertical indicates the direction leaving workers should follow relative to the sun) and its distance and quality (information that is conveyed by the duration that the dance lasts). Also, acoustic signal. Experiments manipulating these characteristics have neatly demonstrated that workers do indeed gather all of this information from their hive-mates.
Environmen: Danger (Vervet monkeys), alarm calls and why different calls?
Vervet monkeys (Chlorocebus pygerythrus), an Old-World monkey of the family Cercopithecidae native to Africa. o Alarm calls - 3 different alarm calls depending on type of predator Different escape responses to 3 different types of predator o As well as simply announcing the presence of danger, many species convey additional information in their alarm calls. In the case of vervets, that is referential information about the type of predator that is approaching. Different calls are valuable to receivers because the best response varies depending on the type of predator: for example, if a leopard approaches, climbing quickly high in a tree is a good option, but putting yourself at the top of a tree is a bad plan if an eagle is flying past. o Signal urgency of the threat (how imminent the threat is)
State: Hunger (Canaries), how do chicks communicate?
o Gape colour- Blood diverted from gut, uncheatable (red=full; yellow=hungry) o Begging - Calls and posture, Honesty maintained by cost Hunger level in chicks is conveyed through various means. One physiological method is through the colour of the gape: this is dependent on the amount of blood flow to this part of the body, which is lowered when the animal has lots of food to digest; blood is diverted to the stomach and the gape appears a paler colour, making this an uncheatable, honest signal to parents. Information on hunger is also available from the begging calls and posture of chicks - the more they beg and the further they reach up, the hungrier they are; the honesty of these signals is maintained because they are costly (both in terms of energy and attracting predators) and so it only pays to do so when chicks are truly hungry.
What are the pay offs for warbler birds in rejecting eggs?
