Lecture A1 (2025-08-26): Animal Behavior and the Scientific Process

In this lecture, we review the scientific foundations of animal behavior. We define a causal question, a hypothesis, a theory, an experiment, and a prediction and how they all relate to each other. We emphasize that a hypothesis is not an IF–THEN statement, but a prediction is. We also cover Tinbergen's four questions (the four different levels of analysis in biology and behavioral ecology). This is all done in the context of talking about the cephalopod eye (with an octopus and a cuttlefish example) and its comparison to the vertebrate/human eye. We end with a short discussion of how to define "behavior" most generally and with the most utility.

Topic highlights:

• cephalopod eye structure
• scientific-process terminology:
  • causal question
  • hypothesis
  • prediction
  • experiment
  • theory
• "Tinbergen's four" (questions/causes), the four levels of analysis:
  • function/adaptation/utility
  • phylogeny/evolution
  • ontogeny/development
  • mechanism (also sometimes called "causation", but I have omitted that from this course as it might be confusing)
• phylogenetic trees
  • chronograms
• evolutionary and developmental constraints between function and mechanism
• the difficulty  in defining "behavior"

Important terms: causal question, hypothesis, prediction, experiment, theory, Tinbergen's four questions (or causes), function/adaptation/utility, phylogeny/evolution, ontogeny/development, mechanism, chronogram

Lecture 0 (2025-08-21): Course Introduction

This lecture introduces BIO 331 (Animal Behavior) and its policies. Most of the lecture covers administrative and structural aspects of the course, but in the middle there is an examination of the "stotting" behavior that occurs in many ungulates where students propose different hypotheses for the phenomenon. The stotting example is meant to motivate the kinds of things that will go on in the course.

Final Exam Review (2024-12-03)

In this lecture, we discuss the upcoming two-stage final exam and review important topics from each of the previous units. Topic highlights:

• reminder of the timeline for the rest of the course
• reminder of the structure of the two-stage final exam
• the different requirements for the different stages of the exam
• suggestions for follow-on courses after BIO 331
• review of important topics from all units in the course, starting from the ones after the midterm

Lecture J1 (2024-11-26): Introduction to Social Behavior and Sociobiology

This lecture introduces students to use of behavioral ecology to study social behavior (and thereby opens the door to the field of sociobiology, the topic of a follow-on course). The lecture starts with a discussion of conspicuous social behaviors seen in collective motion, as in starling murmurations, and discusses how the "selfish herd" hypothesis provides an explanation for these patterns based entirely on benefits to individuals (and not benefits to the group). This discussion motivates a description of the grid of social behaviors that mix costs and benefits to actors with costs and benefits to recipients, including altruism, spite, by-product mutualism, and selfishness. The bottom half of the lecture focuses on introducing inclusive fitness theory (kin selection) as an explanatory framework for understanding some forms of (apparent) altruism, where an individual pays an appreciable cost to perform an action that provides an appreciable benefit to a relative. This allows for introducing the Prisoner's Dilemma from game theory and using it to derive Hamilton's rule, which is a theoretical framework for predicting when benefits to relatives are strong enough to outweigh the costs to the individuals doing them. We then close by applying Hamilton's rule to a parental–investment problem considered by Trivers (first discussed in a prior lecture on parental care) that ends up predicting that offspring may evolve behaviors that lead to over-investment by parents relative to the investment strategy that is best for the reproductive success of the parents.

Topic highlights:

• explanations for collective motion behavior in herds
• taxonomy of social behaviors based on costs and benefits to actors and recipients
• inclusive fitness theory as a gene-centric framework for explaining helping behavior (apparent altruism between individuals)
  • introduction to Hamilton's rule
  • application of Hamilton's rule to an analysis of parent–offspring conflict in parental investment

Important terms: murmuration, selfish herd, domain of danger (or “Voronoi cell”), social exploitation, positive externalities, public good, by-product mutualism, negative externalities, common-pool resources (or open-access goods), Tragedy of the Commons, selfishness, altruism (or cooperation), spite (or altruistic punishment), Prisoner’s Dilemma, inclusive fitness theory (or kin selection), relatedness, direct fitness, indirect fitness, inclusive fitness, Hamilton’s rule, Generalized Hamilton’s rule

Lecture I2 (2024-11-21): Parental Investment and Conflict

In this lecture, we return to the notion that different amounts of physiological reproductive investment can lead to different behaviors. However, whereas we focused on mating behaviors and sexual selection in the previous lecture, we pivot to parental care behaviors here. Parental behavior involves interactions with a wider range of individuals – from multiple offspring (both current and future) as well as other individuals that share in parenting or the fitness consequences of parenting – as well as many more degrees of freedom of behavior. Life history theory, which we introduce in this lecture, provides a framework for understanding consistent behavioral patterns that tend to emerge from different environments. After discussing life history theory, highlight different forms parental behavior and the kinds of opportunities and conflicts that can emerge from them. After discussing topics surrounding infanticide in biparental care, we close with an introduction to classical theories in parent–offspring conflict.

Topic highlights:

• parental care and investment
• life history traits, life history strategies, and life history theory
• sibling conflict, sibling rivalry, and the insurance egg hypothesis
• uniparental, biparental, and alloparental care and relationship to internal and external fertilization
• sexual conflict and infanticide
• parent–offspring conflict

Important terms: anisogamous species, spermatophore, nuptial gifts, Syngnathidae, brood pouch, breeding sail, parental care, parental investment, life history traits, life history strategy, life history theory, 𝑟-selected, 𝐾-selected, sibling conflict, sibling rivalry, insurance egg hypothesis, parent–offspring recognition, external fertilization, egg guarding, mouth brooding, fry, alloparental care, uniparental care, biparental care, maternal care, paternal care, altricial young, joey, precocial young, sexual conflict, infanticide, concealed ovulation, The Bruce effect, parent–offspring conflict, begging, weaning

Lecture I1 (2024-11-19): Reproduction and Mate Choice

In this lecture, we discuss sexual reproduction and how asymmetries in investment can lead to asymmetries in mating behavior among the sexes. We open the lecture with preliminaries and definitions related to the biological description of sexual behavior. We then introduce Bateman's principle and the various downstream predictions of it related to animal behavior. We then pivot to cases which may appear to contradict Bateman's principle. We then close with a discussion of the likely reason why sex evolved and the different functions that mate choice has to provide.

Topic highlights:

• definitions and theories of the adaptive value of sex
• Bateman's principle and evidence both for and against
• examples for the evolution of polygyny, monogamy, and polyandry
• Red Queen Hypothesis and the evolution of sex
• sperm competition
• mate choice, sexual selection, and genetic compatibility

Important terms: sex, meiosis, mating/sexual reproduction, physiological and anatomical differences correlated with the production of different types of gamete, including, primary sexual characteristics, secondary sexual characteristics, somatic cells, gametic cells (or gametes), diploid, haploid (or sometimes monoploid), sperm (or spermatozoa), eggs, “cost of meiosis”, haplodiploid sex-determination system, Bateman’s principle, polygyny, monogamy, polyandry, sperm competition, spermatophore, nuptial gifts, Syngnathidae, brood pouch, breeding sail, Red Queen Hypothesis, anisogamous species, hermaphrodite, protandrous hermaphrodites, protogynous hermaphrodites, isogamous species

Lecture H1 (2024-11-14): Self Defense and Aggression

In this lecture, we discuss fundamentals of self defense from predators. We start with an introduction to mimicry, which allows prey with significant defenses to converge on signals that are easier for larger predators. We also describe prey that do not have significant defenses but can deceptively mimic those organisms that do in order to make themselves appear to be less palatable than they are. This gives us an opportunity to discuss the how mimicry can lead to mimicry complexes embedded in ecological communities. We also discuss other forms of crypsis, including camouflage and hiding, and strategies for providing more time to evade a predator, such as startle behavior and vigilance. We close with an exploration of agonism more broadly and how individuals in agonistic interactions may sometimes choose to fight and other times choose to flee. We use the Hawk–Dove game from game theory to illustrate the balance in such choices and explore a special case of predator–prey oscillations related to a similar negative frequency-dependent selection phenomenon.

Topic highlights:

• mimicry and crypsis
  • Batesian mimicry, Müllerian mimicry, mimicry complexes, camouflage
  • hiding
• startle behavior and vigilance
• agonistic behavior
  • correlated and uncorrelated asymmetries in interactions
• negative frequency-dependent selection
  • evolutionary oscillatory cycles
• Hawk–Dove game
• pure and mixed Nash equilibria in the Hawk–Dove game
• three basic categories of self-defense strategies: avoiding detection, evading capture, and fighting back

Important terms: mimicry, mimic, model, Müllerian mimicry, Batesian mimicry, mimicry complex, aposematism/aposematic signaling, crypsis, camouflage (a form of crypsis), startle behavior, vigilance, agonistic behavior, correlated asymmetries, uncorrelated asymmetries, negative frequency-dependent selection, Hawk–Dove game ("game of chicken"), pure Nash equilibrium, mixed Nash equilibrium, co-evolutionary arms race, three different categories of self-defense strategies