Behavioral Ecology and Altruism: Key Concepts and Genetic Foundations

Behavioral Ecology

The study of how behavior contributes to the survival (fitness) and reproductive success of animals.

Behavior as an adaptive trait

Behavior can be shaped by natural selection because it influences survival and reproduction.

Cost vs benefit framework

Behaviors are evaluated based on whether their benefits outweigh their costs.

Fitness consequences

The effects a behavior has on an individual's survival and reproductive success.

Mutually beneficial (Symbiotic/Transactional)

A behavior where both the actor and recipient benefit; "helps me, helps you." Actor and recipient often rely on each other.

Altruistic behavior

Behavior in which the actor sacrifices its own fitness to help the recipient; "hurts me, helps you."

Selfish behavior (Parasitism)

The actor benefits while the recipient is harmed.

Spiteful behavior

Behavior where harm occurs regardless of consequences; not seen in the animal kingdom and associated with humans.

Darwinian problem of altruism

If natural selection favors individuals that reproduce, it is difficult to explain why individuals sacrifice themselves for others.

Example of Darwin's problem

Sterile workers in insect colonies (ants, termites) help the queen reproduce instead of reproducing themselves.

Inclusive Fitness Theory (W.D. Hamilton, 1964)

An individual’s evolutionary success is determined as the sum of their direct fitness and indirect fitness

Direct fitness

The genetic contribution an individual makes to the next generation through its own reproduction.

Indirect fitness

The genetic contribution an individual makes by helping relatives reproduce.

Hamilton's Rule

Altruism evolves when the genetic benefit to relatives outweighs the cost to the helper.

Hamilton's Rule formula

r × B > C.

r (relatedness)

(Proportion of shared genes)

B (benefit)

Benefit to the recipient

(How many more offspring are produced)

C (cost)

Cost to the altruist

Hymenopterans

Many Hymenopterans (of the order Hymenoptera - ants, bees and wasps) have evolved extreme levels of sociality.

Haplodiploidy

A sex determination system where males are haploid and females are diploid.

Haploid males

Males with one set of chromosomes that develop from unfertilized eggs.

Diploid females

Females with two sets of chromosomes that develop from fertilized eggs.

High relatedness among sisters Diploid Females

In haplodiploid species, diploid females sisters share about 75% of their genes (r = 0.75).

Effect of haplodiploidy on altruism

High relatedness promotes extreme altruism in social insects.

High relatedness (cooperation mechanism)

Individuals are more likely to cooperate with genetically related individuals.

Kin recognition

The ability to recognize relatives and preferentially help them.

Policing behavior

Mechanisms that prevent cheating within groups (e.g., removing eggs from cheating ants).

Spatial structure

Genetically similar individuals cluster together, promoting cooperation.

Reciprocal altruism

Cooperation between unrelated individuals where help is exchanged over time ("I help you now, you help me later").

Example of reciprocal altruism

Vampire bats share blood meals with roost-mates that failed to feed.

Vampire bat survival constraint

A bat that fails to feed may die within 48-72 hours.

Conditions for reciprocal altruism

Repeated interactions, memory of past interactions, and punishment for cheaters.

Altruism is not a contradiction of natural selection - it’s an extension of it, Once we redefine fitness to include relatives, self-sacrifice can make evoluntionary sense. T or F

True

Nature vs nurture in behavior

Behavior is influenced by both genetics and environmental factors.

Interactionist framework

Genes, environment, learning, and evolutionary history all contribute to behavioral development.

Genetic control of behavior

• Genes code for neural development & hormone systems

Genes → proteins → circuits → behavior

Genes produce proteins that form neural circuits that generate behavior.

Genetic knockout experiments

Experiments where specific genes are removed to observe their effects on behavior.

Migratory restlessness in redstarts

Genetic basis of migratory restlessness, characteristic high night-time activity as birds prepare to migrate

Genetic basis of migration

Cross-breeding experiments show hybrids have intermediate migratory restlessness.

fosB gene in female mice

Females with inactive fosB genes show little interest in caring for their pups, relatively normal in their behavior though.

Oxytocin knockout males

Males that cannot produce oxytocin show social amnesia and cannot remember females they recently interacted with.

Age polyethism in honeybees

Honeybee tasks change as they age.

Nurse bees

Younger bees that care for larvae.

Forager bees

Older bees that collect food.

Gene expression differences in bees

About 5.5k (~40% of their genome) genes show different activity between nurse bees and forager bees.

In experimental colonies where old foragers are absent, nurses transition faster! T or F

True (bees)

Juvenile hormone (JH)

Hormone that regulates the transition from nursing behavior to foraging behavior in bees.

Low JH levels

Found in nurse bees.

High JH levels

Found in forager bees.

Removing the JH gland

Delays the transition from nurse to forager.

Applying JH treatment

Speeds up the transition from nurse to forager.

Developmental plasticity

The ability of organisms to develop different traits depending on environmental conditions.

Tiger salamander typical morph

The normal salamander phenotype.

Tiger salamander cannibal morph

A larger morph that develops under crowded conditions with large size differences.

Environmental trigger for cannibal morph

Cannibals only develop when salamander larvae live together, and especially when there are large differences in larval size and when the population largely consists of unrelated individuals

Local adaptation

Behavioral traits evolve in response to local environmental conditions.

Coastal garter snakes

Prefer to eat chemically defensive banana slugs.

Inland garter snakes

Avoid banana slugs because they never evolved the ability to eat them.

Clark's nutcracker seed caching

Birds store up to 33,000 seeds in about 5,000 caches up to 15 miles away.

Cache recovery by nutcrackers

They recover about two-thirds (~3,500 seeds) during winter.

Hippocampus

The brain region responsible for memory and spatial navigation.

Learned taste aversion

Animals associate a food's taste with illness and avoid it in the future.

Rat poisoning difficulty

Rats often avoid foods that previously made them sick.

Rat aversion experiment

Rats developed an aversion to sweet water but not to lights or sounds associated with illness.

Preparedness hypothesis (Seligman, 1970)

the preparedness hypothesis, which argues that different species will have evolved different capabilities to form associations as a result of evolutionarily selective pressures.

Prepared associations

Associations animals easily learn due to evolutionary history.

Contraprepared associations

Associations animals struggle to learn because their brains are not adapted for them.

Unprepared associations

Associations that are not natural but can still be learned through conditioning.

Cooperation problem

The question of why selfish individuals do not dominate cooperative systems.

Game theory

A framework used to analyze strategic interactions between individuals.

Prisoner's dilemma

A situation where individuals choose whether to cooperate or defect, with different consequences.

Iterated interactions

Cooperation is more stable when individuals interact repeatedly.

Tit-for-tat strategy

Start by cooperating, then copy the partner's previous behavior.

Kin selection

Helping relatives because they share genes.

Reciprocity

Mutual cooperation based on repeated interactions.

Reputation and punishment

Cheaters develop bad reputations and may be punished or excluded.