A Historical Perspective to B.E.

A Historical Perspective to B.E.

The field of Animal Behavior was fairly well established in the 1960’s when some began to look at behaviors with a different perspective.

Behavioral Ecology is a mixture of Ethology (Animal Behavior), Ecology, and Evolutionary Theory.

Historical Perspective cont’d

In Behavioral Ecology emphasis is put on the value of a behavior to an organism’s fitness

Function is emphasized as opposed to the “cause” of the behavior

Fitness – reproductive success, or the number of your genes that get passed on to future generations is the criteria used to measure biological success.

Inclusive Fitness

Fitness is based on “related-ness” (r) or the number of genes that you share with another.

The r value is 1 in terms of relatedness to yourself (an identical twin has ALL your genes so your relatedness to them would be 1).

Inclusive Fitness cont’d

Your parents each have half the same genes you do, so for parents r = 0.5

Similarly, your siblings each share half of your genes, so for siblings r = 0.5

For grandparents, r = 0.25

For first cousins, r = 0.125 (1/8), etc.

Direct vs. Indirect

Organisms can exhibit direct fitness, by passing genes through their own fitness

Organisms can exhibit indirect fitness by passing genes on through related children (helping raise related children).

Ex. Having a child yourself (r = 0.5), and helping a sibling to have a child (r = 0.125) increases your fitness to 0.625

Putting it togetherSo, Inclusive Fitness = Direct Fitness + Indirect Fitness

This idea was first discussed by W.D. Hamilton

He was talking about altruistic behavior (decreases fitness of actor while increasing fitness of recipient).

Described Hamilton’s Rule: Altruistic behavior will only occur when the inclusive fitness of the actor will eventually increase due to the altruistic action.

So if the actor is not related to the recipient the only time to be altruistic is if there is a reasonable expectation of getting the same in return. (ex. alarm call in flock of birds)

Back to Historical PerspectiveIn the 1800’s, Animal Behavior was studied by two very different groups of researchers.

Europe: Ethology was developed, and emphasis was placed on the functional aspects of behavior. Field research and observation were favored.

North America: Practiced by Psychologists, emphasis was placed on causation. Controlled experiments in laboratories were favored.

These two schools of thought did not agree on much, but over time they began to cooperate and synthesize their ideas into what we know today as Modern Ethology.

History cont’dIn 1973 three famous and very different Animal Behaviorists jointly shared a Nobel Prize for their contributions to the modern understanding of Ethology. They were:

Konrad Lorenz: studied imprinting in Graylag Geese

Karl von Frisch: studied communication in bees (Waggle Dance)

Niko Tinbergen: studied gulls, stickle backs (fish) and wasps and many topics in Animal Behavior.

Imprinting

Konrad Lorenz carried out famous studies of imprinting behavior in Graylag Geese.

Young goslings imprint on their mother in first few days of life, follow her and learn basic goose behaviors.

Imprinted Canada Geese Goslings

Imprinting cont’d

However, goslings will imprint on a human substitute (or an object such as a toy truck) if exposed to the correct stimuli (large object that moves away slowly).

Imprinting occurs in a short sensitive period and is irreversible.

Imprinting cont’d

Bee CommunicationIt was suspected (based on observations) that “scout” bees could communicate the location of a good food source to the worker bees of the hive, but no one could understand how that might happen.

Karl von Frisch worked on that problem.

While observing the behavior of the scout bees when they returned to the hive, he noticed that they always walked in circles waggling their abdomens. This he dubbed the waggle dance, and started relating the attributes of the dance to the newly found food source. Through hard work and good record keeping, he discovered how the bees communicated.

von Frisch

Waggle DanceSo, it turns out that vertical in the hive is the direction of the sun, and all bees innately understand that.

The angle to vertical that the bee waggles is the angel (to the sun, outside) that indicates the direction of the food source.

The length of the waggling indicates the distance to the food source.

Fixed action pattern (FAP)

Fixed Action Pattern is a sequence of behaviors that is essentially unchangeable and once begun, is always completed.

Niko Tinbergen studied FAP in three-spined sticklebacks. Males have red bellies and defend territories from other males. But they will attack any small unrealistic model fish so long as it has a red belly.

Fixed action pattern (FAP)

Red belly is a “releaser” that causes stickleback to initiate its defensive response.

Fig 51.4

Proximate QuestionsProximate questions focus on mechanisms and development of behavior.They are “how” questions.For example: How does a bird learn its species song? Or How does a plant know when to produce flowers?Possible hypotheses that address these “how” questions include:Males learn their species song by listening to what their father sings andFlowering in plants is triggered by increasing daylight.

Ultimate QuestionsAre “why” questions.

They ask why natural selection favors a certain behavior and not others. Ultimate hypotheses generally suggest that the behavior enhances fitness, through

For example: Why do female birds prefer males with brighter plumage?

Or Why do birds look up occasionally when they are feeding?

Ultimate Questions

Ultimate hypotheses that might address these “why” questions include:

Females prefer males with brighter plumage because such males possess genes that confer disease resistance (sickly birds won’t have bright plumage).

Birds look up to scan for predators, which enhances their survival.

Tinbergen’s RulesNiko Tinbergen developed the 4 Questions of behavior that must be answered for any thorough study of a behavior.

What is the behavior’s function ?

What causes the behavior to occur ?

How does the behavior develop ?

What is the evolutionary or phylogenetic history of the behavior ?

Infanticide among Lions

A researcher notices that when taking over a pride, the new male lion will kill all the offspring of the previous male, and asks the question, why.

Lions cont’dBackground:

Lions live in groups called Prides• Many adult females and cubs

• All the adult females are related to each other

• All the adult males are related to each other, but not to the females

Males leave the natal pride at about 3 years of age, females do not leave

Female’s job is to reproduce and feed the pride

Male’s job is to protect the pride and invest in pride fitness (donate DNA).

Males (sometimes traveling with a brother) become “nomads” until they can physically take over a pride.

• Nomads hunt together and search for vulnerable prides (males 7 yrs or older)

• The take over precipitates the killing of existing cubs (killed, not eaten)

• Females then come into estrous in 9 months rather than the normal 25 months

• Male copulates with all adult females, all will get pregnant at same time, so all births occur at same time. Increase survival from shared care.

• Incoming new male will increase his fitness

Lions cont’d

So, why do males kill the existing cubs?Animal Behaviorist: The lion kills the cubs because of the unfamiliar smell.

Behavioral Ecologist: The lion kills the cubs to increase his own fitness.

What do you say?

Adaptive Significance of Behaviors

Behaviors evolve, and Behaviors with the most positive influence on fitness will be passed on.

Since natural selection works on behavior, there is behavioral variation.

Let’s look at migratory behavior in the Blackcaps (Sylvia atricapilla)

Migratory Orientation in Blackcaps

European Blackcaps migrate to Western Africa. Asian Blackcaps migrate to Eastern Africa. (so, Blackcaps from SW Germany migrate in SW direction and those from Hungary in a SE direction).

Researchers can assess the direction birds choose to migrate using an Emlen funnel.

Birds spend most time in part of funnel that faces in direction they want to migrate.

Blackcap Migration Map

Emlen Funnel

Migratory Orientation in Blackcaps

Members of the two populations were crossed and produced offspring.

Offspring’s orientation was tested in an Emlen funnel.

Mean orientation of offspring south which is strong evidence that there is genetic control of migration.

Black Triangles: Eastern European Adults (SW)White Triangles: Western European Adults (SE)Black Dots: Offspring (S)

So, Behavioral Ecology is…Behavioral Ecology is the study of an individual’s genetic fitness on their behavior

The major behaviors involve in an organism’s fitness are related to:

Predator avoidance

Foraging

Reproduction (including Migration and Territory Selection)

Such behaviors occur within the context of an organism’s ecology and Life History Strategy.

Life History StrategyA Life History Strategy is the affect of all decisions regarding the allocation of time and energy on reproductive fitness over the lifespan of the individual.

These decisions can be made through Natural Selection or by Direct Individual Decision

Decision Examples1. Traditional (Natural Selection based)

At what age should an organism begin to reproduce How many offspring at once

r – selected (many offspring (generally smaller), little to no parental care) k – selected (few offspring (generally larger), lavish parental care)

How long is the reproductive lifespan

Ex. Iteroparity vs. Semelparity in species of Lobellia (scrub plant).

- Iteroparity is the ability to have several generations in a year

- Semelparity is the ability to have only one generation in a year

Lobellia telekii semelparous Lives on dry rocky slopes 1000’s of seeds

Lobellia keniensis iteroparous Lives in moist valley bottoms 100’s of seeds

Decision Examples cont’d2. Non – Traditional (Direct Individual based)

a. Foraging decisions: what to eat/where to eat

b. Mate Choice: monogamy vs. polygamy

c. Migration Choice: when, where, or if

d. etc.

Cost vs. Benefit TradeoffsLife History Strategy decisions involve a cost/benefit analysis.

Ultimately, these decisions will be determined by Natural Selection (one way or the other will be better for fitness)

These decisions result in compromises that ultimately optimize the reproductive fitness over a lifetime.

The decisions occur on two levelsEvolutionary phylogenetic level (age of reproductive readiness)

Level under direct individual control (where to forage)

Both levels involve exclusively genetic control and control exerted by the environment or genetic make-up.

Tradeoff’s and CompromisesSince the ultimate idea here is reproductive fitness, sometimes organisms are required to choose between future reproductive potential and current reproductive success.

Ex. Douglas Fir TreeWhen conditions are good (plenty of sunlight and water) more energy goes into growth than reproduction (banking on future reproductive potential). Fewer cones are produced.

When conditions are poor (usually lack of water or some other environmental disaster) the trees put more energy into reproduction and less into growth (focusing on current reproductive success). More cones are produced.

Examples of some Different Behaviors

Innate Behavior: Kinesis

Kinesis: strong change in activity or turning rate in response to stimulus.

Woodlice become more active in dry areas and less in humid areas. Helps to keep them in moist areas and move out of dry.

Woodlouse Movement

Innate Behavior: Taxis

Taxis is movement towards or away from a stimulus.Cockroaches demonstrate negative phototaxis (move away from light).Trout demonstrate positive rheotaxis and face towards the current in a stream.

Positive Rheotaxis

Environment Modifies BehaviorHabituation

Loss of responsiveness to stimuli that do not convey useful information (“cry wolf” effect).

Associative Learning. Many birds learn quickly that Monarch butterflies taste foul and will avoid them after an initial experience.

Rats will permanently avoid a food if after eating some of it they subsequently become nauseated.

Spatial learning. Many animals modify their behavior depending on the environment they live in.

In stable environments landmarks are useful for navigating.

Minimizing predation risk while foraging.

There are numerous ways in which organisms attempt to minimize their risk of predation.

These include: avoiding habitats that are the most dangerous, foraging in groups and spending time looking for predators.

Predation/Avoidance

Many animals group together to avoid predation.

Grouping increases chances a predator will be spotted before it can attack. Grouping also increases time spent foraging as individuals have to scan less often in a group.

Experiments by Kenward using a trained Goshawk showed that as flock size increased wood pigeons detected an

approaching bird at greater distances.

Kenward Wood Pigeon Study

Kenward Wood Pigeon Study

Enhancing reproductive success

Males and females generally differ in optimal reproductive strategies.

The sex that invests more in the offspring (usually female) is the choosy sex.

Hamster egg and sperm

Enhancing reproductive success

Investment includes energy invested in young and time spent caring for and guarding the young.

Choosy sex has limited capacity to produce more young.

Enhancing reproductive success

Choosy sex maximizes reproductive success by requiring other sex to provide resources (e.g. territory, food) or by choosing the best possible mate for its genes.

Non-choosy sex maximizes reproduction by mating more often.

Monogamy

Type of mating system observed influenced by whether both parents needed to rear young.

In most birds young need lots of care so monogamy is common and both parents participate in caring for young.

Polygamy

When one sex can care for the young polygamous (many gametes) mating systems are common (e.g. most insects, elk, elephant seals, some birds e.g. grouse, peafowl, jacanas) and individuals mate with multiple mates.

Polygyny, Polyandry are examples.

Bull Elk with harem

Competition for mates

Generally, members of the non-choosy sex compete to either control choosy’s by defending them (e.g. elk, elephant seals, phalaropes) or to attract females to mate (peafowl, grouse).

By maximizing number of times they mate they maximize reproductive success.

Competition for mates

Sperm competitionMales compete not only to mate with females, but frequently engage in sperm competition as well.

More sperm a male can insert the higher his chances of fertilizing eggs (like a lottery).

In species with lots of sperm competition males have proportionally larger testes than males of monogamous species.

Sperm competition

Males also commonly remove other males’ sperm (e.g. damselflies have a penis with spines), plug up females’ reproductive tract (many insects) or guard females against other males.

Alternative mating strategies

Paracerceis isopods (a type of crustacean) live inside sponges.

There are 3 genetically different male types.

Alternative mating strategies

Alpha males large and defend harems of females.

Beta males pretend to be females.

Gamma males are tiny and sneak inside harems undetected.

Mate choice

Females are very choosy about which male they mate with.

For example, in polygynous species, such as sage grouse, a few males obtain almost all the matings and most males fail to mate.

Sage Grouse Mating Ritual

Birds of ParadiseFemale birds assess male

plumage quality (symmetry and color) and display quality (duration and intensity) in evaluating males.

(Male Raggiana Bird ofParadise displaying.)

Male display and male quality

Considerable evidence that male’s ability to grow attractive plumage and engage in vigorous displays are indicators of males genetic resistance to disease and parasites.

By choosing such males, females ensure their young will receive high quality genes.

Similarly, female stalk-eyed flies

prefer males with the longest eye stalks.

Male display and male quality

Various genetic disorders are correlated with flies inability to develop long eyestalks. Females who avoid such males enhance genetic quality of their offspring.

Kin Selection

Natural selection favoring the spread of alleles that increase the indirect component of fitness is called kin selection.

Kin selection is expected to operate most strongly among close relatives

Belding’s Ground Squirrels

Belding’s Ground Squirrels breed in colonies in Alpine meadows.

Males disperse, but female offspring tend to remain and breed close by. Thus, females in colony tend to be related, but males other than offspring are not.

Belding’s Ground Squirrels

Belding’s Ground Squirrels

Long term study by Sherman of marked animals of known relatedness.

Analysis of who called showed that females were much more likely to call than males.

Belding’s Ground Squirrels

In addition, females were more likely to call when they had relatives within earshot.

Belding’s Ground Squirrels