Organismal-Behavior Flashcards
Tinbergen’s four ‘why’ questions
To determine WHY a behavior occurs, determine the:
1) Causation: What is the immediate cause of the behavior? (proximate)
2) Development or ontogeny: How has this behavior developed? (proximate)
3) Adaptive advantage or function: What makes this behavior beneficial? (ultimate)
4) Evolutionary history or phylogeny: How did this behavior arise in evolutionary history? (ultimate)
Behavior p. 2
Applications of Tinbergen’s ‘why’
1) Starlings sing because increasing length of day triggers hormones/air flows through vocal apparatus (causation), because they have learned songs from their parents and neighbors and have a predisposition to learn the song of their own species (development/ontogeny), to attract mates for breeding as singing increases reproductive success (adaptive advantage), because the most primitive living birds make very simple sounds, so it is reasonable to assume that the complex songs of starlings and other song birds have evolved from simple ancestral calls (Evolutionary history/phylogeny)
2) Sperm whales produce codas by pushing air past phonic lips in the nasal complex (causation) and they learn coda patterns from other whales through social learning (development/ontogeny), these codas allow recognition between and amongst clans (adaptive advantage), and this likely evolved from the use of echolocation in odontocetes to produce clicks similar to codas (Evolutionary history/phylogeny).
Behavior p. 2
Proximate
Causal and developmental factors of behavior
Behavior p. 2
Ultimate
Why and how the individual has evolved behavior
Behavior p. 2
Causal explanations of behavior
1) Concerned with mechanisms
2) E.g. Female lions are synchronous in oestrus because of chemical cues and take-overs by males
3) E.g. young die when new males take over pride because of abortion and infanticide or eviction
Behavior p. 5
Function explanations of behavior
1) Concerned with why mechanisms are favored by natural selection
2) 2) E.g. Female lions are synchronous in oestrus because this increases cub survival, young males survive better and have greater reproductive success when they leave pride in a group
3) E.g. young die when new males take over pride because females come into oestrus more quickly when cub is killed and males remove older cubs that may compete with his young
Behavior p. 5
How to show that behavior has a genetic basis?
1) In order for behavior to be adaptive, behavior must be heritable
2) In drosophila, different individual foraging behavior (between rovers and sitters) are caused by differences in alleles of the for gene. In honeybees, switch in behavior within individuals is caused by changes in for gene expression. So if gene acts similarly across taxa, it likely is heritable?
3) Blackcaps in Germany are highly migratory, but in Canary Islands are sedentary. When breeding these two populations, offspring showed intermediate migratory restlessness, indicating genetic control.
Behavior p. 8-9
Wynne-Edwards model of group selection
1) Idea that behavior serves the group, not the individual, to ensure survival of the species and that groups containing selfish individuals die out because they exploit food resources
2) Largely discredited because groups do not go extinct fast enough for group selection to be an important force in evolution
3) Individuals will die fast than groups, so individual selection is likely the predominant evolutionary force of behavior
4) Immigration and emigration also reduce likelihood of selfish behavior, because their genotype would likely not spread throughout whole population and lead to fixation
Behavior p. 11-12
Empirical support against group selection
1) Most tits lay 8-9 eggs
2) Chicks in larger broods are fed less often and weigh less
3) But tit clutch size is slightly less than what would be expected to optimize number of surviving young per brood, why?
4) In an experiment where a tit was given “free chicks”, “free eggs”, and “full costs”
5) No difference in chick survival between treatments, but difference in female survival
6) There is a trade-off between increased reproductive effort and adult survival
7) Provides support for individual regulation of clutch size, rather than regulation of clutch size for the good of the group (reduced resource exploitation)
Behavior p. 14-15
Optimal trade-off between survival and reproductive efforts
1) Pianka and Parker 1975; Bell 1980
2) When plotting current reproductive effort with expectation of future reproductive success, if the curve is convex iteroparity and repeated breeding is favored (because the higher the effort, the lower the future success)
3) If the curve is concave, semelparity or big bang reproduction is favored because future reproductive success is consistently low
Behavior p. 16
Phenotypic plasticity
Ability of a single genotype to alter its phenotype in response to environmental conditions
Behavior p. 18
Reaction norm (phenotypic plasticity)
When the phenotypic variation is continuous, the relationship between phenotype and the environment for each genotype. There may be variation in both the elevation of the line (trait value) and its slope (the way trait value changes in response to environment.
Behavior p. 19
How to test behavior
1) Comparison between individuals within a species
2) Experiments
3) Comparison among species
Behavior p. 24-5
Comparative method of testing behavior
1) Because different species have evolved in relation to different ecological conditions and so comparison among species may help us to understand how different pressures shape behavior
2) Correlating species differences in behavior with differences in ecology
3) How does this differ from natural selection field studies?
4) Limitations: Need to consider alternative hypotheses (e.g. how do we know that the selective pressure we selected is the one that actually results in observed behavior), need to quantify ecological variables, need to infer cause and effect, observed behavior could be non-adaptive when we are inferring adaptive behavior, independence in statistical analysis (are you comparing one species to a whole genus?)
Behavior p. 25, 31
Examples of comparative method
1) Social organization of weaverbirds.
a) Species in forests tend to be insectivorous. Food is dispersed so they are solitary feeders that defend large territories. Because of dispersed food source, both parents must take care of young so they are monogamous. Since both males and females visit the nest they must have similar, dull plumage.
b) Species living in the savannah tended to eat seeds, which are patchy in distribution and locally superabundant. Therefore feeding in flocks is beneficial as a group can cover a greater search area and the patches can support more than one individual. Because food is abundant, females can feed their young alone, so they are polygamous and sexual dimorphism in plumage has evolved.
2) Social organization of African ungulates.
a) Small ungulates have a higher metabolic requirement per weight and need high quality food (berries and shoots) which tend to occur in the forest and are widely dispersed, so they must be solitary foragers
b) Large ungulates can eat poor quality food in bulk and are less selective. It is not economical to defend large areas for food supplies so they wander in herds to find large patches of food. The largest male can monopolize many females in the herd.
Behavior p. 29-30
How has sexual dimorphism evolved?
1) Two hypotheses: (a) Sexual dimorphism allows males and females to exploit different niches OR (b) male-male competition for mates favors larger individuals.
2) If a were true, then dimorphism would be more common in monogamous mating systems where males and females forage together
3) But the opposite pattern is seen, so b is the more likely reason
Behavior p. 35
Testis size and breeding system
Larger testes are typically indicative of sperm competition, as animals with polygamous mating systems often have larger testis
Behavior p. 37
Phylogenetic effects in comparative studies
1) Closely related species tend to have similar traits since they descended from common ancestors rather than independent evolution.
2) Adding a similar species to an analyses increases the likelihood that the trait being tested, you increase the probability of that trait being correlated across species.
3) Therefore, it is necessary to take phylogenies into account.
4) Independent contrasts may be a solution to this problem
Behavior p. 38
Independent contrasts
1) Solves the problem when species are not independent
2) We can assume that species have evolved independently since their divergence.
3) For example, in a phylogeny where A gave rise to B and C, B gave rise to D and E, and C gave rise to F and G, the independent contrasts would be A and B, D and E, and F and G.
Optimality approach for behavior
Seeks to predict which particular trade-off between costs and benefits will have the maximum net benefit to the individual
Behavior p. 47-8
Marginal value theorem
1) Animals experience diminishing returns within a patch
2) Used to predict how much time an animal foraging for itself will spend in each site before moving on
3) E.g. The optimum load for foraging starlings depends on the travel time (fixed) and search time, for longer trips the optimal load is higher than shorter trips. Fig 3.2
4) E.g. Travel time predicts the length of time fly spends copulating with female (since if two males mate with a female, the second male has a higher percentage of offspring so males want to guard females) Box 3.1
5) E.g. Bees collect less food for longer distances because the load slows them down.
Behavior p. 54
Optimal prey choice model
1) A predator encounters two prey types: prey 1 and prey 2. If prey 1 is more profitable E1/h1 > E2/h2, or rather the ratio of energy density to handling time of prey 1 is greater than prey 2.
a) if prey 1 is encountered it will eat,
b) but if prey 2 is encountered it should eat only if the abundance of prey 1 is so low such that E1/(h1+S1) < E2/h2, or the added search time of prey 1 makes the pay off for prey 2 better.
2) Therefore this model makes three predictions:
a) The predator should either just eat prey 1 (specialize) or eat both prey (generalize)
b) The decision to specialize depends only on the search time of prey 1, the more profitable prey
c) The switch from specialization to generalization is immediate once S1 increases such that E1/(h1+S1) < E2/h2 is true.
Behavior p. 61
What is the ‘currency’ of optimal prey choice models?
Handling time, energy density, and search time.
What is risk-sensitive foraging?
1) Risk of starvation is an additional currency that can be included in optimal prey choice models.
2) Animals are sensitive to both the return rate on a foraging opportunity but the variability (in prey availability)
3) E.g. Juncos were given a variable prey option, in which pay off varied from 0 to 6 seeds, and a fixed rate of .5 seeds. When their energetic needs were higher (at low temperatures) they risked the variable option because the fixed rate did not provide enough energy to avoid starvation. At higher temperatures with lower metabolic costs, birds selected the fixed food resource.
4) E.g. A small bird needs to put on energy reserves by dusk in order to survive the night. The prey options are one unit of food with probability 1 or two units of food with probability .5, so average pay-offs are the same but there is a greater variance. It’s decision will therefore depend on its current state (>=8 they survive). If the state is 6, it will take the gamble, but if the state is 7 it will play safe since that will give it just what it needs to survive without risking starvation. (Box 3.3)
5) E.g. When nests are depleted of resources, bees increase risky behavior. When nests are augmented with additional resources, bees play it safe.
Behavior p. 63-4
What is the currency of foraging?
Food return and food requirement
Balancing predation and starvation in tits
When predators (hawks) are introduced, great tits reduced their mass. Additionally, more dominant birds (that have greater access to food and a less variable environment of foraging) dropped substantially more weight. Behavior p. 66
What is the utility of optimality models?
1) Make testable predictions
2) Assumptions regarding currency and constraint are explicit
3) Generalizes simple decisions facing animals
Behavior p. 79
Social cognition
1) The ability of an animal to behave as though it could interpret the knowledge of another individual.
2) E.g. when scrub jays are observed by other birds while caching, it would later on move its cache to avoid stealing. This happened more frequently when the observer was a more dominant bird than the cacher.
Behavior p. 71
Mental time travel
1) The ability to project into the future, independently of current physiologic requirements
2) E.g. Scrub jays, when given the option to store food in a series of three rooms where they were held in sequence, typically hid the food in the room where they would be kept overnight so they could eat if hungry at that time
Behavior p. 72
Evidence against animal intelligence
1) Complex behaviors can be generated by simple behavior mechanisms
2) Intelligent behavior may be a specific adaptation to a particular ecological problem, such as the memory of food storing birds
3) Even humans use subconscious rules of thumb rather than conscious calculations
Behavior p. 73
Social learning
1) Using the behavior of others as a source of information
2) E.g. nine-spined sticklebacks (more at risk of predation) rely on public information to find the appropriate patch to forage in, but three-spined sticklebacks (less at risk of predation) rely only on their own experiences.
Red Queen Evolution
1) Evolving to keep up with rivals.
2) E.g. When Daphnia were exposed to parasites from the same sediment layer (contemporary parasites) and from sediment layers with past and future parasite populations, infectivity was higher with contemporary parasites than with parasites from previous growing seasons. Therefore, Daphnia evolved to beat past parasite genotypes while the parasites, in turn, rapidly evolved to adapt to the changing host genotypes.
Behavior p. 84
Polymorphic cryptic coloration
1) Different colour forms exist within same species
2) Polymorphic prey prevents search image use by predators
3) Experiments on jays support this as detect prey easier when shown images of prey with the same coloration repeatedly when compared to switching the morph/coloration of prey in successive trials
Behavior p. 87,89
Search images (predator)
When predators improve their ability to see cryptic prey by searching for similar “patterns” against camouflage
Behavior p. 88
Apostatic selection
rarer prey types have an advantage
Behavior p. 89
How does prey polymorphism evolve?
In a population, abundance of most cryptic form increases (since predators initially go for more conspicuous forms), until an equilibrium is reached where previously cryptic form is most abundant, and two other morphs persist, Fig 4.6
Behavior p. 90
Does slight concealment (crude crypsis) of prey have an advantage?
1) Yes, in an experiment where Great tits were presented with inedible twigs, large cryptic prey (meal worm in a straw), and small conspicuous prey, they often chose small conspicuous prey because the time it took to distinguish the twig from the large cryptic prey was not an optimal decision
2) Handling time increases with crude crypsis
Behavior p. 91
Disruptive coloration
When coloration “breaks up” the body outline to further disguise prey and confuse predators
Behavior p. 92
Countershading
Darker coloration on dorsal surface, giving the prey a “flat” appearance as shadows won’t show
Behavior p. 93
Masquerade
Resemblance of inedible objects, camouflage without crypsis.
Behavior p. 94
Aposematism
1) Honest signaling of toxicity through bright coloration
2) Conspicuous colors help predators to learn to avoid unpalatable prey
3) Costs of aposematism vary depending on predation pressure and trade-offs between investing in repellent defenses versus colorful signals.
Behavior p. 96-97, 103
Evolution of aposematism
1) Plausible that conspicuous colors evolved first via sexual selection, but that these conspicuous colors increased predation risk, so distastefulness evolved secondarily.
2) Plausible that unpalatability evolved first followed by conspicuousness, specifically in family groups. Essentially a mutation for bright coloration evolves in a distasteful species, the predator then only has to eat one individual with the bright coloration to learn that it is unpalatable, therefore the bright colored individuals survive via kin selection.
3) Grouping may have evolved after warning colors.
Behavior p. 98-99
Mimicry
Association between bright colors and repellent defenses has led to the evolution of Batesian and Mullerian mimicry
Behavior p. 100
Mullerian mimicry
1) Repellent species look alike
2) Promotes uniformity in color pattern
Behavior p. 100
Batesian mimicry
1) Cheating by palatable species
2) Promotes polymorphism because mimetic patterns will be at an advantage when rare relative to the model (when predators are more likely to eat noxious models) and at a disadvantage when common (predators more likely to sample palatable mimics)
Behavior p. 102
Evolution of cuckoo brood parasitism
Cuckoos parasitize nests by mimicking their eggs. The hatched cuckoo then throws the other eggs in the nest out. Cuckoos have evolved in response to hosts through the use of mimetic eggs, timing of laying, and unusually fast laying. Hosts have evolved to discriminate between their own eggs and that of a parasite and have evolved more distinctive egg patterns. However, discrimination at the chick stage is too costly.
Behavior p. 106-8
Evolutionary Stable Strategy (ESS)
1) A strategy that, if all members of a population adopt it, cannot be improved by a alternative strategy
2) E.g., If one person at an outdoor concert stands, then everyone must stand.
3) Not necessarily an optimal strategy, but strategy at which system settles where cheaters cannot dismantle it
4) Population behavior depends on community composition (frequencies of each strategy reach a point where average payoff is equal, making the system stable)
Behavior p. 116
Hawk-Dove Game
1) Hawks always fight to injure opponents
2) Doves always share the resource
3) Dove versus dove, resource is split evenly and each animal accrues equal fitness benefit
4) Dove versus hawk, dove accrues no fitness
5) Hawk versus hawk, both incur injuries so fitness benefit is equally decreased
6) Hawk versus dove, hawk wins and accrues all possible fitness
7) Each strategy does best when rare
Behavior p. 117
Ideal free distribution
1) Ideal = having perfect knowledge, Free = free to move
2) Assumes that animals know ideal habitat and are free to go anywhere and will not be hindered from going to new location
3) E.g., distribution of ducks in a pond
4) Can test either numerical prediction, equal intake prediction, or prey risk predation
5) Assumes stochasticity (equal intake prediction better suited for stochastic environment, e.g. male dung flies competing for mates)
Behavior p. 119-122
Despotic distribution
1) Resource defense
2) First competitors settle in rich habitat, second competitors settle in poor habitat, and final competitors must find new habitat
3) E.g., Great tits use oak woodland for breeding in spring, but last competitors must use hedgerows where there is less food and lower breeding success
Behavior p. 123
Ideal free distribution with unequal competitors
1) Subordinates distribute themselves relative to the behavior of the despots
2) E.g., habitat selection in aphids, want to occupy large leaves to create galls because number of progeny depends on resources utilized, additional settlers can choose to pick share resources on large leaf or smaller leaf solitarily
Behavior p. 123-4
Economic defensibility
1) Resource or territory is defendable if cost of maintenance is smaller than benefit
2) If resources are at low density, gains of excluding others may not outweigh the costs
3) May be an upper threshold of resource availability beyond which defense is not economical, e.g. many intruders
4) E.g., Gill and Wolf’s sunbirds (past certain threshold, high nectar levels are not protected as territorial defense does not save foraging time.
Behavior p. 126
Alternative strategy
1) Genetically based decision rule (e.g. always sneak or always fight)
2) Good to be rare, e.g. spice finches have a higher frequency of scroungers, as it continues to increase the pay-off decreases and producers will be favored
Behavior p. 132, 139
Conditional strategy
Individuals vary their competitive behavior depending on something like body size (e.g. fighting in horned beetles, horns only grow past certain body size)
Behavior p. 132
Tactic
Behavior pattern displayed as part of strategy.
Behavior p. 132
Conditional strategies with alternative tactic
1) Natterjack toads: callers and satellites
2) large toads are callers, small toads are satellites
3) but behavior varied based on degree of competition for larger males
Behavior p. 133
Sinervo’s lizard mating morphs
1) rock paper scissors
2) orange lizards are aggressive and defend large territories
3) yellow males look like females
3) blue males are less aggressive and defend small territories
4) frequency of morphs depends who the winner is
Behavior p. 141
Pros of group living
1) Protection from climatic extremes
2) Advantages in locomotion
3) Reducing predation
a) Dilute risk of attack
b) Predator confusion
c) Communal defense
d) Improved vigilance for predators
4) Improving foraging success
a) Better food finding (information centers)
b) Better food capture (group hunting)
Behavior p. 148
Cons of group living
1) More conspicuous to predators
2) higher attack rate per group (not per individual)
Behavior p. 148
Dilution theory
1) Groups lower the probability of attack for an individual
2) E.g., winter aggregations of monarch butterflies. Although not a very palatable butterfly, birds will still attack them when they roost, predation rate per individual still lower in groups
Behavior p. 148-9
Predator swamping
1) Synchrony in time swamps the predator’s ability to capture prey
2) E.g., individual mayflies are safest from predation during days when more adults emerge (could be argued this synchronized mating increases breeding success, but it is also seen in parthenogenetic flies).
Behavior p. 150
Selfish herds
1) Individuals that approach each other reduce their domain of danger
2) E.g., swarms, flocks, and shoals as individuals try to gain safest position in the group
3) E.g. fur seal experiment with sharks
Behavior p. 151
Predator confusion
1) Grouping confuses predator attacks
2) E.g., increasing prey shoal size decreases success of predator attack
Behavior p. 151
