Comprehensive Study Notes on Animal Behavior: Proximate and Ultimate Causation, Ultimate Causation, Learning, Evolution, and Sociobiology
Fundamental Principles of Animal Behavior
Definition of Behavior: Behavior encompasses the actions carried out by muscles under the control of the nervous system. This includes physiological processes and systems, such as a bird using throat muscles for song, an animal releasing scent to mark territory, or a crab waving a claw. All animal physiology contributes to behavior, and behavior reciprocally influences physiology.
Adaptive Nature of Behavior: Behavior is essential for acquiring nutrients, finding reproductive partners, and maintaining homeostasis (e.g., honeybees huddling to conserve heat). Being critical for survival and reproduction, behavior is subject to natural selection, which also shapes anatomy used for recognition and communication.
Fiddler Crab Anatomy and Behavior: Male fiddler crabs (genus Uca) exhibit extreme asymmetry, with one claw reaching up to half the mass of their entire body. This enlarged claw serves as a weapon to repel males and as a tool for courtship to attract females. After luring a female to his burrow, the male seals her inside with mud or sand for mating.
Proximate and Ultimate Causation
Tinbergen's Four Questions: Dutch scientist Niko Tinbergen established four fundamental questions to understand any behavior. These are categorized into proximate and ultimate causation:
Proximate Causation: Focuses on "how" a behavior occurs.
What stimulus elicits the behavior, and what physiological mechanisms mediate the response?
How does the animal's experience during growth and development influence the response?
Ultimate Causation: Focuses on "why" a behavior occurs in the context of natural selection.
How does the behavior aid survival and reproduction?
What is the behavior's evolutionary history?
Behavioral Ecology: This is the study of the ecological and evolutionary basis for animal behavior, centering on the concept of ultimate causation.
Fixed Action Patterns and Migration
Fixed Action Pattern (FAP): A sequence of unlearned acts directly linked to a simple stimulus. FAPs are essentially unchangeable and, once initiated, are usually carried to completion.
Sign Stimulus: The external cue that triggers a FAP.
The Three-Spined Stickleback (Gasterosteus aculeatus): Tinbergen observed that males of this species attack other males with red bellies. The red color acts as the sign stimulus; males will attack even unrealistic models if they have red undersides but will ignore realistic fish models lacking red.
Migration: A regular, long-distance change in location guided by environmental cues. Navigation methods include:
Solar Navigation and Circadian Clocks: Animals track their position relative to the sun. An internal circadian clock (a -hour activity rhythm) allows them to adjust for the sun's changing position throughout the day.
Stellar Navigation: Nocturnal animals may use the North Star due to its constant position.
Magnetic Navigation: Homing pigeons can navigate on overcast days using Earth's magnetic field. Placing a magnet on a pigeon's head prevents efficient return to its roost.
Behavioral Rhythms
Circadian Rhythm: A daily cycle of rest and activity synchronized with light and dark cycles. It persists even under constant conditions, such as during hibernation.
Circannual Rhythms: Behavioral rhythms linked to the yearly cycle of seasons, such as migration and reproduction. These are often influenced by day length (photoperiod) rather than direct food intake.
Lunar-Linked Rhythms: Some behaviors correlate with the lunar cycle. Fiddler crab courtship is linked to the new and full moon, synchronizing reproduction with the greatest tidal movements to facilitate the dispersal of larvae into deeper waters.
Animal Signals and Communication
Signals and Communication: A signal is a stimulus transmitted from one organism to another. Communication is the transmission and reception of these signals.
Modes of Communication:
Visual: Use of body form, color, or movement.
Chemical: Detection of odors or tastes.
Tactile: Touching to alert others to presence or intent.
Auditory: Use of sound or songs.
The Fruit Fly (Drosophila melanogaster) Courtship Ritual: This involves a stimulus-response chain:
Visual and Chemical: The male identifies a female and detects airborne chemicals she releases.
Tactile: The male touches the female with a foreleg.
Auditory: The male vibrates a wing to produce a species-specific courtship song.
Honeybee (Apis mellifera) Dance Language: Deciphered by Karl von Frisch, foragers use symbolic movements to communicate food locations:
Round Dance: Used if food is close (); involves tight circles and abdomen movement, prompting a general search nearby.
Waggle Dance: Used for distant food. The dance resembles a figure eight. The angle of the straight run relative to the hive's vertical surface indicates the horizontal angle of the food relative to the sun. The number of abdominal waggles in the straight run indicates distance.
Pheromones: Chemical substances used for communication, especially in mammals and insects.
Reproductive Function: Female silkworm moths release pheromones detectable by males from several kilometers away.
Social Order: The honeybee queen produces a "queen substance" that attracts workers, inhibits their ovary development, and attracts drones during mating flights.
Alarm Signals: Injured minnows or catfish release an alarm substance from their skin. Nearby fish aggregate at the bottom in tightly packed schools. Just of fathead minnow skin can trigger a reaction in of water.
Innate Behavior and Learning
Innate Behavior: Developmentally fixed behavior where nearly all individuals in a population behave alike (e.g., FAPs, pheromone signaling).
Learning: The modification of behavior resulting from specific experiences. It involves memories formed by changes in neuronal connectivity.
Cross-Fostering Studies: An experimental approach where the young of one species are raised by adults of another.
California Mice (Peromyscus californicus) vs. White-Footed Mice (Peromyscus leucopus): California mice are highly aggressive and provide high parental care; white-footed mice are the opposite. Cross-fostering showed that California mice raised by white-footed mice became less aggressive and provided less care to their own future offspring, demonstrating environmental influence across generations.
Twin Studies: Compare identical twins raised apart vs. together to explore the influence of genetics and environment on human disorders like schizophrenia, alcoholism, and anxiety.
Specific Types of Learning
Imprinting: The establishment of a long-lasting behavioral response to a specific individual or object during a sensitive period.
Greylag Geese: Young goslings identify the first moving object they see as "mother." If they spend their first hours with a human, they will follow that person and ignore their biological mother.
Conservation Applications: Whooping cranes (Grus americana) raised by sandhill cranes imprinted on the wrong species and failed to mate with other whooping cranes. Modern programs use "crane suits" and ultralight aircraft to teach migration routes without improper imprinting.
Spatial Learning: Establishing memory based on the environment's spatial structure.
Digger Wasps (Philanthus triangulum): Tinbergen demonstrated that female wasps find their hidden nests using visual landmarks (e.g., a ring of pinecones). Moving the landmarks causes the wasp to fly to the wrong location.
Cognitive Maps: Representations of spatial relationships between objects. Clark's nutcrackers retrieve hidden seeds by remembering the halfway point between landmarks rather than a fixed distance.
Associative Learning: Linking one environmental feature with another.
Classical Conditioning: An arbitrary stimulus becomes associated with a particular outcome (e.g., Pavlov's dogs salivating at a bell sound).
Operant Conditioning (Trial-and-Error): An animal associates its behavior with a reward or punishment (e.g., a rat pressing a lever for food). Blue jays learn to avoid monarch butterflies after vomiting due to the butterfly's foul taste.
Biological Constraints: Evolution restricts certain associations. Pigeons can associate danger with sound but not color; rats associate illness with smells but not sounds.
Complex Cognition and Social Learning
Cognition: The process of knowing, involving awareness, reasoning, recollection, and judgment. Shown in honeybees through abstract thinking (distinguishing "same" vs. "different" patterns).
Problem Solving: Devising a method to overcome an obstacle. Examples include chimpanzees stacking boxes to reach a banana and ravens pulling up food on a string.
Development of Learned Behaviors:
Song Learning: White-crowned sparrows have a sensitive period ( days) to hear the song, followed by a "subsong" phase, before the song "crystallizes." Canaries can learn new song syllables throughout their lives.
Social Learning: Learning by observing others.
Chimpanzees: Young learn to crack oil palm nuts with stones by watching elders.
Vervet Monkeys (Chlorocebus pygerythrus): They use distinct alarm calls for leopards (bark), eagles (cough), and snakes (chutter). Infants learn to use these calls accurately through adult reinforcement; they initially call at any bird but eventually only at dangerous eagles.
Culture: A system of information transfer via social learning or teaching that influences behavior across a population.
Evolution of Foraging and Mating Behavior
Foraging: Activities used to search for, recognize, and capture food.
Genetic Variation: In Drosophila, the forager () gene exists as (Rover) and (Sitter). High population densities favor long-distance foraging (), while low densities favor short-distance ().
Optimal Foraging Model: Proposes that selection favors behavior that minimizes the costs of foraging (energy, predation risk) and maximizes the benefits (nutrition).
Northwestern Crows: Drop whelks from an average height of , which math models show is the optimal balance between flight energy and shell-breaking success.
Mule Deer (Odocoileus hemionus): They forage predominantly in open areas despite lower food quality compared to forest edges because the risk of predation from mountain lions is significantly lower in the open.
Mating Systems:
Monogamous: One male and one female. Often show little sexual dimorphism.
Polygamous: One sex mates with several of the other.
Polygyny: One male, many females. Males are often showier/larger (e.g., elk).
Polyandry: One female, many males. Females are often more ornamented (e.g., red-necked phalaropes).
Parental Care and Paternity: Certainty of paternity is higher with external fertilization (e.g., jawfish), leading to more frequent male parental care. In internal fertilization, male care is less common unless necessary for offspring survival (e.g., most birds).
Sexual Selection and Game Theory
Mate Choice:
Intersexual Selection: Females often choose males based on traits (long eyestalks in flies, bright colors in birds) that signal health and vitality.
Mate-Choice Copying: Guppy females (Poecilia reticulata) may choose a less colorful male if they observe a model female courting him.
Male Competition: Agonistic behavior involves ritualized contests for resources. These contests reduce actual injury (e.g., kangaroos boxing, stalk-eyed flies facing off).
Game Theory: Evaluates alternative strategies where the outcome depends on the strategies of others.
Side-Blotched Lizards (Uta stansburiana): Three male throat colors/strategies persist in a "rock-paper-scissors" dynamic:
Orange-throat: Aggressive, large territories.
Blue-throat: Territorial, small scale.
Yellow-throat: Nonterritorial, female mimics ("sneaky").
This is an example of frequency-dependent selection.
Altruism and Inclusive Fitness
Altruism: Behavior that reduces individual fitness but increases the fitness of others (e.g., Belding's ground squirrel alarm calls, sterile worker bees, nonreproductive naked mole rats).
Inclusive Fitness: The total effect of spreading genes through one's own offspring and by aiding close relatives' offspring.
Hamilton's Rule: Natural selection favors altruism when .
: Benefit to the recipient (extra offspring produced).
: Cost to the altruist (fewer offspring produced).
: Coefficient of relatedness (fraction of shared genes).
Kin Selection: Natural selection favoring altruism that enhances the reproductive success of relatives.
Relatedness values (): Siblings/Parents = ; Aunt/Niece = ; First Cousins = .
Reciprocal Altruism: Aiding non-relatives with the expectation of returned favors. Common in stable social groups (e.g., chimpanzees, humans).
Tit for Tat: A behavioral strategy where an individual mimics the previous action of their partner (cooperating first, then reciprocating or retaliating).
Sociobiology: The discipline exploring the evolutionary basis of social behavior, pioneered by E. O. Wilson in . It suggests that behaviors like play might serve as preparation for unexpected life events.
Questions & Discussion
Greylag Goose Egg Retrieval: If an egg rolls out, the mother retrieves it with her beak. If the egg is removed mid-process, she continues the motion anyway. This is a fixed action pattern triggered by the sign stimulus of the egg; the motor program must be carried to completion once initiated.
Minnow Alarm Substance Responses: Some species might respond like minnows because they share the same predators. Others might increase activity to flee quickly, and some might show no change if the alarm substance does not signal a threat to their specific species or if they have different defense mechanisms.
Fiddler Crab vs. Plant Rhythm: Both mechanisms use environmental cues (lunar cycle for crabs, seasonal photoperiod for plants) to synchronize biological processes (reproduction/dispersal for crabs, flowering for plants) with optimal external conditions for offspring/pollination success.
Speciation and Learned Behavior: Learned behaviors, such as species-specific songs or mate-choice copying, can lead to reproductive isolation. If populations learn different songs, they may no longer recognize each other as potential mates, eventually leading to the formation of new species.
Altruism Beyond Reproductive Age: Selection for altruism can still occur if the post-reproductive individual aids the survival and success of their kin (e.g., grandchildren), thereby increasing their own inclusive fitness by ensuring their shared genes are passed on.
Scientific Skills Exercise: Crow Foraging:
Whelk Drop Dependence: The average number of drops required to break a shell decreases sharply as platform height increases from to . Above , there is little further decrease in the number of drops needed.
Energy Efficiency: Total flight height (drops height) is a measure of energy. At , the total flight height is lowest because it requires the fewest total meters climbed to achieve success. At , too many drops are needed; at , the climb is unnecessarily high.
Observations vs. Model: Crows prefer a drop height of . This is remarkably consistent with the quantitative model's prediction that is the energy-minimizing height.
Larger Whelks: Crows likely favor larger whelks because they contain more food (biomass) and may require less total energy to break relative to the nutritional reward.