Observation: Wasps can relocate their inconspicuous nests.

Question: How do digger wasps relocate their nests?

Example of hypothesis testing:

Niko Tinbergen observed that digger wasps could return to their exact nest location after spending considerable time away (ignoring the 100s of other nests at the same location).

Question: How do digger wasps relocate their nests?

Hypotheses:

The wasp returns to any nest.

The wasp uses chemical scents to relocate the nest.

The wasp uses visual landmarks to relocate the nest.

Tinbergen further observed that when wasps left the nest, they spent time flying back and forth around the nest entrance.

Null hypothesis: visual landmarks are not used to relocate the nests.

Tests & Predications:

1. If I modify the visual landmarks around the nest, the wasp will not be able to find it.

2. If I move the landmarks (keeping them intact), the wasp will return to the wrong location.

3. If I give the wasp landmarks (pine cones), she will use them to relocate her nest.

Important to only manipulate one thing at a time!!

Results:

1. Wasps took much longer to find their nests if landmarks were manipulated.

2. If landmarks were moved to a new location (intact), the wasp searched for her nest in that new location.

3. Experimental manipulation of landmarks allowed us to predict where the wasp would look for her nest.

Conclusions:

The wasp probably uses visual landmarks to relocate the nest.

Why say probably?

Was this an example of a proximate or ultimate question?

Observation: Adult black-headed gulls remove broken egg shells from their nests.

Question: Why do gulls remove broken egg shells?

Another example of hypothesis testing:

Tinbergen was not interested in the mechanisms of egg shell removal (how they were recognized), but why they were removed (in an evolutionary sense)

Question: Why do gulls remove broken eggshells?

Hypothesis:

Broken egg shells attract predators to the nest.

Tests & Predications:

The presence of broken egg shells increases the probability of nest predation.

Results:

The presence of egg shells near the nest increased the probability of predation.

Conclusions:

Black-headed gulls (or some ancestor) likely evolved the behavior of removing eggs shells to reduce the probability of their nests being located by predators.

Why say probably?

What are some alternative testable hypotheses?

Scientific Method

Humans have been using this method in some form for a long time.

- Discriminated data from theory- Developed hypotheses- Used reasoned skepticism

Blurton-Jones (1976) documented Kalahari bushmen’s (!Kung) knowledge of animal behavior

Hunter-gatherer society, similar to most of human’s history.

“When asked whether newborn cape buffaloes stayed with their mothers or were kept hidden, one man replied that he had not looked ‘since buffaloes kill you, you don’t go after them.’ However, he then suggested that since buffaloes are like cows, and newborn

These are examples of comparative (behavior same as similar species - phylogenetic) and ecological (based on interactions with the environment) hypotheses.

calves stay with their mothers, the same would be true of buffaloes. Or, that since newborn buffaloes are large and conspicuous, the option of trying to stay hidden wouldn’t work very well.”

Limitations of Science

- Restricted to those things that can be logically tested and falsified.

- More than one hypothesis can predict the same outcome of a test.

- Results can be interpreted in different ways, leading to different conclusions.

- Hypotheses constantly being reevaluated and modified as more results and information are gained.

What is Animal Behavior?

The study of how and why animals interact with each other (both within and among species) and their environment.

Proximate questions - howmechanisms responsible for interactions

Ultimate questions - whyhow these interactions influence an individual's survival and reproduction.

Ultimate reasons

Proximate reasons

Species are groups of interbreeding organisms.

(organisms potentially capable of reproducing naturally among themselves, and producing viable offspring)

Biological Species Concept (E. Mayr)

What is a species?

Genetic diversity - Amount of genetic variation within or among populations of a given species.

Genetic diversity, along with environmental variation (gene by environment interaction), determines phenotypic diversity.

Population—All organisms of the same kind found within a specific geographic region. (have the potential to interact)

Evolution

The process of change in the traits of populations over time.

Evolution does not occur within an individual.

Evolution does not occur within a generation.

Traits must have genetic basis.

Evolution is the change in allele frequencies in a population over time

Mechanisms of Evolution:

Mutation

Genetic Drift

Migration

Natural Selection

Sexual Selection

Evolution by Natural Selection

First proposed by Charles Darwin in On the Origin of Species, 1859

1. There must be variation among individuals of a species.

2. This variation must be heritable.

3. This variation must lead to differential reproduction.

Adaptive evolution occurs primarily through natural selection

Natural Selection is the process that determines which individuals within a species will reproduce and pass their genes to the next generation.

Evolution in action

Pepper Moths in England

Light colored moths easy for birds to see on soot-covered tree, dark colored moths harder to see

Increasing pollution led to soot-covered trees without lichens

By 1950, most moths black

•Evolution does not just happen on long time scales

•Evolution is important for real-word issues: agricultural, conservation, health

* Disease dynamics

* Invasive species issues

* Antibiotic and pesticide/herbicide resistance

Coevolution:

When two or more species interact closely they can influence

each other’s evolutionary direction. In tightly coevolved interactions, evolutionary change in one species will lead to evolutionary change in other or the second species may go extinct.

Red Queen Hypothesis

Lewis Carroll's Through the Looking Glass: “in this place it takes all the running you can do, to keep in the same place."

Examples: host / parasite coevolution predator / prey dynamics

How does evolution by natural selection affect behavior?

Although not physical traits, behaviors do have heritable, genetic variation that leads to differential reproductive success.

Therefore, natural selection has shaped behaviors that we see today.

Why do new males commit infanticide?

Hanuman langurs

lions

Hypothesis 1: infanticide is a social pathology that is caused by overcrowding and misplaced aggression.

Hypothesis 2: infanticide leads to increased reproductive success for the male.

Hypothesis 3: infanticide is a population regulatory mechanism that prevents overpopulation

Hypothesis 1: infanticide is a social pathology that is caused by overcrowding and misplaced aggression.

Predictions -

Males should kill females and juveniles as well as infants

Infanticide should occur more frequently when densities are high.

Not supported by data.

Hypothesis 2: infanticide leads to increased reproductive success for the male.

Predictions -

Males should kill infants that are not related to him.

Killing unrelated infants should increase a males reproductive success. (fitness)

Common estimates of reproductive success:

number of surviving offspring

number of matings obtained

survival rates

feeding rates

Data:

Males kill unrelated infants (present when they take over a group).

Females go into estrous more quickly.

More food available for male’s offspring.

Hypothesis 3: infanticide is a population regulatory mechanism that prevents overpopulation

“for the good of the species”

Predictions -

Infanticide should occur more frequently when densities are high.

Group Selection

V.C. Wynne-Edwards

Animal Dispersion in Relation to Social Behavior (1962)

Populations of self-sacrificing individuals would survive and outcompete populations

of selfish individuals

Can natural selection act on groups or populations rather than individuals?

Individual vs. Group Selection

G. C. Williams

Adaptation and Natural Selection (1966)

Natural selection will act more strongly on the individual at the expense of the group.

Group selection is therefore not evolutionary stable. Open to selfish individuals and

cheating.

Conditions necessary for group selection:

very low migration between groups

founding groups small or related

group extinction rates near individual death rates.

Alcock’s book takes an adaptationist approach.

Does all behavior need to be explained in terms of natural selection?

Other explanations:drift, founder events, learning/cultural transmission, ecological or genetic constraints, by-product other processes.

(note - these other processes still based on evolutionary principles)