Lesson 17: Animal Behavior and Behavioral Ecology

Behaviour: what animals do, and why it pays

Ethology studies animal behaviour in natural settings. Every behaviour can be asked about at two levels: *how* (mechanism — stimuli, nerves, hormones) and *why* (function — how it raises survival or reproduction). Confusing the two levels is the beginner's classic error; a complete answer uses both (Tinbergen formalised this into four questions, adding development and evolutionary history).

Innate and learned behaviour

Innate behaviour is inherited and stereotyped: fixed action patterns (a greylag goose rolling a lost egg back to the nest, even completing the motion if the egg is removed mid-roll), reflexes (Lesson 12), and taxes/kinesis (woodlice moving faster in dry air until they blunder into damp — no direction sense needed, yet it keeps them in moist habitat). Learned behaviour modifies responses with experience:

• Habituation — stopping responding to a repeated harmless stimulus (birds ignoring a scarecrow — which is why scarecrows fail).
• Imprinting — rapid, critical-period learning (goslings follow the first moving object they see: normally mother; in Lorenz's famous experiments, Lorenz).
• Classical conditioning — associating a neutral stimulus with a significant one (Pavlov's dogs salivating to a bell).
• Operant conditioning — learning from consequences (Skinner's rats pressing levers for food; the basis of animal training and much of education psychology).
• Insight learning — solving a new problem without trial and error (Köhler's chimpanzees stacking boxes to reach bananas).

Data: habituation measured

A snail withdraws into its shell when its dish is tapped. Withdrawal duration after each tap: 12 s, 9 s, 7 s, 5 s, 3 s, 2 s, 1 s, 1 s. The response decays smoothly — a learning curve. Present a *new* stimulus (a light tap on a different surface) and withdrawal jumps back up: dishabituation, proving the snail has not merely tired — it has learned to classify the original tap as harmless. Distinguishing fatigue from learning with a control test is exactly the experimental logic exams reward.

Communication and signals

Animals signal with sound (birdsong, whale song), vision (peacock tails, threat postures), chemicals (pheromones — ant trails, moth mating), and touch. Signals evolve to be honest when deception is costly or detectable: a male frog's deep croak genuinely requires a large body, so females can trust it as a size advertisement. Communication coordinates everything from mating to alarm: meerkats post sentries whose alarm calls are predator-specific — different calls for eagle and snake, producing different escape responses in the group.

Social behaviour and altruism's puzzle

Many animals live in groups: costs (competition, conspicuousness, disease) against benefits (diluted predation risk, shared vigilance, cooperative hunting, communal care). The puzzle is altruism — sterile worker bees, alarm-calling meerkats, vampire bats sharing blood meals. Kin selection solves much of it: a gene promoting help to relatives spreads because relatives share copies of it (Hamilton's rule: help evolves when rB > C — relatedness × benefit exceeds cost). Sterile castes make sense for haplodiploid ants and bees, where sisters share 75% of genes. Bat blood-sharing is reciprocal altruism: help today, repaid tomorrow, with cheats remembered and excluded — cooperation policed by memory.

Worked example: Hamilton's rule in numbers

A ground squirrel gives an alarm call: calling raises her own risk, costing C = 0.1 in expected future offspring, but warns three sisters (r = 0.5 each) whose survival benefit totals B = 0.3 offspring equivalents each. rB per sister = 0.5 × 0.3 = 0.15; total = 0.45 > C = 0.1 → calling is favoured by selection *through the genes' perspective*, even though it endangers the caller. The arithmetic explains why alarm calls are commonest in groups of close kin.

Foraging: behaviour as economics

Optimal foraging theory predicts animals maximise energy gained per unit time/risk: starlings carry more prey per trip when the feeding patch is far from the nest (loading up amortises the journey — demonstrated by watching parents' loading curves match predictions). Shore crabs preferentially break open medium mussels — large ones cost too much handling time per calorie. Behaviour, quantified, becomes testable economics.

Biology in the real world: conservation and welfare

Behaviour guides practice: captive-breeding programmes use imprinting knowledge to avoid human-imprinted animals that cannot breed or be released (costumed keepers feed condor chicks with puppets); wildlife crossings are placed where movement studies show animals travel; understanding conditioning improves guide-dog training and reduces human–wildlife conflict (aversive conditioning teaches bears to avoid towns without killing them).

Common misconceptions

• Instinct does not mean "unchangeable" and learning does not mean "intelligent." Fixed patterns can be modulated; simple learning (habituation) occurs in animals with a few hundred neurons.
• Animals are not little humans. Attributing human motives ("the dog feels guilty") is anthropomorphism; the guilty look is a response to the owner's cues, demonstrated experimentally. Explain behaviour by stimuli, history and function.
• Altruism is not a paradox once genes are the bookkeeping unit — bodies can lose while gene copies win through relatives.

Exam Experience

Question 1. A young gosling follows a human keeper as it would its mother. This is an example of —

• A. operant conditioning
• B. imprinting
• C. habituation
• D. insight learning

Question 2. Birds gradually stop reacting to a scarecrow. This decrease in response to a repeated harmless stimulus is —

• A. classical conditioning
• B. imprinting
• C. habituation
• D. a fixed action pattern

Question 3. Sterile worker bees helping their queen is best explained by —

• A. the workers hoping to reproduce later
• B. kin selection: workers share genes with the queen's offspring
• C. group selection acting alone
• D. learned behaviour from the queen

Answers. 1: B. 2: C. 3: B.

Constructed response. Researchers find that meerkats on sentry duty give alarm calls, and groups with sentries spend 25% more time feeding and lose fewer pups to predators; sentries are usually well-fed individuals and call rates do not depend on how closely related the group members are. (a) Give two benefits of sentry behaviour to the group (1 point). (b) Explain why sentry behaviour can evolve even without kinship, referring to the state of the sentry (2 points). (c) Distinguish between a proximate (how) and ultimate (why) explanation of the alarm call (2 points). Scoring guide. (a) Any two: more feeding time, fewer losses to predation, earlier warning (1 pt total for two). (b) Well-fed sentries pay a low personal cost (they are not losing feeding time they need) (1 pt); the whole group, including the sentry, gains protection — the sentry is actually safer on watch having spotted danger first (1 pt). (c) Proximate: the sentry sees a predator silhouette, its nervous system triggers the call (1 pt); ultimate: calling increased ancestors' survival/reproductive success so call-promoting alleles spread (1 pt).

Going deeper: migration and navigation — behaviour at continental scale

Migration is behaviour stretched over thousands of kilometres, and its mechanisms stack every level of this lesson. Navigation uses layered cues: a sun compass corrected by an internal clock, star patterns learned in youth, landmarks and smell — and a magnetic sense: many birds detect Earth's magnetic field, probably via light-sensitive chemistry in the retina. Preparation is physiological: migrants gorge (some double their weight), shrink gut and other organs to save flight weight, and moult into fresh feathers. Arctic terns fly pole to pole (~70,000 km/year, two summers a year, ~30 years) — the most extreme commuter on Earth. The function question (why) has a seasonal-energy answer — breed where summer food explodes, winter where survival is possible — but climate change (Lesson 18) is decoupling the timing: birds arriving on the ancestral schedule now miss the caterpillar peak (phenology mismatch again, this time in behaviour).

Going deeper: behavioural experiments — controlling the variables

Ethology's classic experiments are models of control. To test whether a gull chick's pecking at its parent's bill is innate and stimulus-bound, Tinbergen presented cardboard models varying one feature at a time: chicks pecked most at a red spot on a long thin bill — and even more at an exaggerated artificial "supernormal" stimulus (a giant red-spotted stick), proving the response is released by specific *sign stimuli*, not by recognising "mother". To test learning in wasps, Tinbergen moved landmarks around a nest entrance and watched returning wasps search at the displaced landmark — landmark learning demonstrated by moving pine cones. The method lesson generalises: change one variable, keep the animal's motivation constant, and beware anthropomorphic interpretation (the chicks were not "deceived emotionally"; a releasing mechanism was triggered).

Worked example 2: territory economics

A robin defends a territory when the benefits (exclusive food and nesting space) exceed the costs (singing time, injury risk). As food density rises, optimal territory size shrinks — owners tolerate closer neighbours because a small rich patch beats a large poor one — a prediction confirmed in field studies of several bird species. Territory is a budget, and behaviour is accounting.

Final check: Tinbergen's four questions, applied

The complete ethology toolkit in one example — a male stickleback attacking a red-bellied model. Mechanism (how): the red underside is a sign stimulus releasing aggression via visual pathways and hormones. Development: males raised in isolation still attack — the response is largely innate, tuned by experience. Function (why): repelling rival males defends the nest and eggs, raising reproductive success. Evolutionary history: the response is shared across stickleback populations and relatives, elaborated from ancestral territorial defence. Any behaviour question can be answered at the wrong level (describing hormones when asked about function) — so the first move in an exam is to classify what is being asked. The four questions also close the course's argument: mechanism is Lessons 12–15, development is Lesson 15, function is Lesson 8, history is Lesson 6 — behaviour is where the whole syllabus meets in a single animal.