BIO WEEK 8: Behavioral Ecology: Communication & Sexual Selection (Part 1)

What Is Behavior?

how and why organisms respond to stimuli in their environment.

Two key components:

• Response

• Environmental stimulus

Examples studied:

• Finding food

• Choosing habitat

• Navigation

• Communication

• Sexual selection

• Cooperation & altruism

Proximate Causation

“HOW”

Mechanistic explanation.

Example:

• How does a pigeon find its way home?

Possible mechanisms:

• Infrasound detection

• Magnetic compass

• Visual landmarks

These are immediate physiological or neurological mechanisms.

Ultimate Causation

“WHY”

Evolutionary explanation.

Why does a pigeon return to the same place?

Because:

• Returning increases survival

• Increases reproductive success

• Natural selection favored individuals that homed successfully

Important:
Behavioral choices are usually not conscious evolutionary decisions — they are shaped by natural selection over generations.

Communication

exchange of information between organisms.

Can occur:

• Within species

• Between species

networks evolve.

Communication Network Model

Three components:

1. Sender

2. Receiver

3. Environment

The environment influences how signals travel and how they are perceived.

Honest vs Deceptive Communication

Example from slides:

• Coral snake (poisonous)

• King snake (harmless mimic)

• Predator (e.g., red-tailed hawk)

This is Batesian mimicry

Definition:
A harmless species mimics a harmful one.

Honest Message:

“I am poisonous.” (Coral snake)

Deceptive Message:

“I am poisonous ;)” (King snake)

Receiver responds:
Leaves snake alone.

Important concept:
Not all communication is truthful.

Does Communication Benefit Both Parties?

Not always.

Sometimes:

• Sender benefits

• Receiver benefits

• Both benefit

• Or one is manipulated

Signal

A trait that evolved specifically to convey information.

Maintained by natural selection because:

• It affects receiver behavior

• It increases sender fitness

Can be:

• Behavioral

• Morphological

• Physiological

Example:
Bird song
Bright coloration
Courtship displays

Cue

Information that is:

• Present

• Useful to receiver

• But did NOT evolve for communication

Example:
Predator smells prey.
Prey did not evolve scent for predator benefit.

Which benefits the sender?

Signal

Cue primarily benefits the receiver.

Honest Signal

Provide accurate information.

Example:
Bright coloration that truly signals toxicity.

Deceptive Signals

Provide misleading information.

Example:

• Batesian mimic.

can evolve if:

• It increases fitness

• It is not too common (otherwise predators stop responding)

Communication Evolves

systems shaped by:

• Natural selection

• Receiver psychology

• Environmental constraints

• Conflict of interest between sender and receiver

Cost–Benefit Analysis

In behavioral ecology, this evaluates whether a behavior’s benefits outweigh its costs (energy, risk, time).

Anisogamy

A reproductive system where gametes are different sizes:

• Small, mobile sperm

• Large, nutrient-rich eggs

This difference drives many patterns of sexual selection.

Intrasexual Competition

Competition between individuals of one sex for access to mates of the opposite sex.

Commonly refers to members of one sex competing to be chosen by the other.

(Usually male competition for female choice.)

Frequency-Dependent Selection

The fitness of a trait depends on how common or rare it is in the population.

• Sometimes rare traits have an advantage

• Can help maintain variation in a population

Eavesdropping (in animal behavior)

When an individual observes interactions between others and uses that information to guide its own behavior.

Example: A male watching two rivals fight and choosing whether to challenge the winner.