Comprehensive Study Guide on Behavioral Ecology and Evolutionary Foundations and Social Systems
Foundations of Behavioral Ecology
Behavior represents the totality of an animal's actions and the methods by which those actions are performed. This encompasses muscular activities, such as chasing prey or singing, but also includes non-muscular activities like the secretion of pheromones and the process of learning.
Levels of Behavioral Causation
Scientific inquiry into animal behavior differentiates between immediate mechanisms and long-term evolutionary significance.
Proximate Causation: These are referred to as "how" questions. They focus on the immediate environmental stimuli that trigger a behavior, along with the genetic, physiological, and anatomical mechanisms involved. For example, a proximate investigation of bird breeding might explore how increasing day length affects hormone production.
Ultimate Causation: These are "why" questions that address the evolutionary significance of a behavior. They explore why natural selection favors a specific trait in terms of survival and reproductive success. Using the same bird example, an ultimate explanation would be that breeding in the spring ensures an ample food supply for the offspring, maximizing reproductive success.
Genetic Influences on Behavior
Behavior is an expression of an animal's phenotype, resulting from the complex interplay between genetics and environment. Some behaviors are developmentally fixed, known as innate behaviors, which occur despite variations in the environment.
Kinesis: A simple change in activity or turning rate in response to a stimulus. For instance, sowbugs move more in dry environments and less in humid ones, increasing their chances of remaining in moisture.
Taxis: An automatic, oriented movement toward (positive) or away (negative) from a stimulus. An example is positive rheotaxis in stream fish, which automatically swim upstream to face the current, aiding in food capture and preventing them from being swept away.
Migration: Periodic long-distance travel, often genetically programmed. Research on the blackcap (Sylvia atricapilla) reveals that migratory restlessness is inherited polygenically. Cross-breeding migratory and non-migratory populations results in offspring with intermediate migratory behavior.
Animal Communication and Signaling
Communication involves the transmission and reception of signals—behaviors that cause a change in another animal's behavior. The type of signal used is often adapted to an animal's environment and lifestyle.
Visual and Auditory Signals: Frequently used by diurnal species like birds. Humans prioritize these signals because of our own sensory biases.
Chemical Signals (Pheromones): Common in insects and mammals. For example, honeybee queens use pheromones to maintain social order. Minnows release an alarm substance from skin glands when injured, causing nearby fish to school tightly and stay vigilant. Pheromones are effective even at extremely low concentrations.
Tactile and Electrical Signals: Used by various species depending on their ecological niche.
Genetic Control of Songs: While many birds learn their songs, insect mating songs are often under direct genetic control. In Drosophila, males produce species-specific songs through wing vibration, and hybrids produce songs with elements from both parent species.
Behavioral Neurogenetics: The Case of the Vole
Research on voles demonstrates how a single gene can influence complex social behavior.
Prairie Voles (Microtus ochrogaster): These rodents are monogamous. Males help care for young and form strong pair-bonds after mating. This behavior is mediated by the neurotransmitter arginine-vasopressin () and its receptor, the receptor.
Montane Voles: Related species that are promiscuous and lack the same receptor distribution.
Transgenic Evidence: When the prairie vole receptor gene is inserted into lab mice, the mice exhibit the receptor distribution and social behaviors characteristic of prairie voles.
Environmental and Developmental Factors
Behavior is highly plastic and can be modified by experience and environment.
Dietary Influence: In Drosophila mojavensis, the type of cactus larvae consume affects the hydrocarbons in their exoskeleton, which in turn influences female mate choice.
Cross-Fostering Studies: California mice are monogamous and aggressive, while white-footed mice are not. If newborn California mice are raised by white-footed parents, they become less aggressive and provide less parental care as adults, showing lower levels of in the brain.
Learning: The modification of behavior based on specific experiences.
Habituation: The loss of responsiveness to repetitive, unimportant stimuli (the "cry wolf" effect), allowing the nervous system to focus on meaningful cues.
Spatial Learning: Modification of behavior based on the spatial structure of the environment. Digger wasps use landmarks to find their nests. Sticklebacks from stable pond environments rely more on landmarks than those from river environments.
Cognitive Maps: Internal representations of spatial relationships. Corvids (crows and jays) use these to locate thousands of hidden food caches.
Associative Learning: Linking one stimulus to another. This includes classical conditioning (associating a neutral stimulus with a reward/punishment, like Drosophila avoiding scents paired with shocks) and operant conditioning (trial-and-error learning).
Animal Cognition and Problem Solving
Cognition involves the ability of the nervous system to perceive, store, and process information.
Problem Solving: High-level cognition seen in primates, dolphins, and corvids. Chimpanzees, for instance, learn to solve problems by observing others.
Bird Song Development: Many songbirds have a sensitive period (a critical time for learning). White-crowned sparrows must hear the song of their species during this time to develop a normal song later. The process involves a "subsong" phase where the bird compares its own singing to its memory of the adult song.
Evolution of Behavior in Natural Populations
Behavioral variation within species often reflects evolutionary adaptations to different environments.
Prey Selection: Coastal garter snakes (Thamnophis elegans) eat slugs, whereas inland populations do not. This preference is genetic; 73% of naive coastal newborns attack slugs compared to only 35% of inland newborns.
Aggression in Spiders: Funnel web spiders (Agelenopsis aperta) in arid, food-poor habitats are more aggressive and return to foraging faster after disturbance than those in resource-rich riparian forests, where predation risk from birds is higher.
Foraging Genes: In Drosophila melanogaster, the for gene has two alleles: for^R (rover) and for^s (sitter). Low-density populations favor sitters, while high-density populations favor rovers who travel further to find food.
Optimal Foraging and Mating Systems
Natural selection favors behaviors that enhance survival and reproduction.
Optimal Foraging Theory: Predicts that animals will forage in a way that maximizes energy intake while minimizing costs (energy used, predation risk). Crows drop whelks from a specific height to minimize the total energy needed to break the shell. Bluegill sunfish select larger Daphnia only when prey density is high enough to justify the choice.
Mating Systems:
Monogamy: One male, one female. Common in birds where young require dual-parent care.
Polygyny: One male, many females. Common in species with showy, dimorphic males.
Polyandry: One female, many males. Associated with dimorphic females.
Certainty of Paternity: Influences parental investment. In species with internal fertilization, males are less certain of paternity and provide less care. In external fertilization (common in fish and amphibians), certainty is higher, and male parental care is far more frequent (rising from 7% to 69% in across families).
Sexual Selection and Game Theory
Sexual selection results from differences in mating success.
Intersexual Selection: Choice by one sex (usually females) based on traits like the long eyestalks of flies or colorful feathers, which may signal health.
Intrasexual Selection: Competition within one sex. In the marine isopod Paracerceis sculpta, three male types (alpha, beta, gamma) use different strategies to mate, all achieving approximately equal success overall.
Game Theory: Models strategies where the outcome depends on the actions of others. Side-blotched lizards (Uta stansburiana) have three throat colors (orange, blue, yellow) that cycle in dominance like a game of rock-paper-scissors based on their relative abundance.
Altruism and Inclusive Fitness
Altruism is behavior that decreases an individual's fitness while increasing the fitness of others.
Inclusive Fitness: Proliferating one's genes by reproducing and by helping relatives raise offspring.
Hamilton's Rule: Natural selection favors altruism when the benefit to the recipient (), weighted by the coefficient of relatedness (), exceeds the cost to the altruist ():
Kin Selection: The mechanism of inclusive fitness involving aid to relatives. Seen in Belding's ground squirrels, honeybees, and naked mole rats.
Reciprocal Altruism: Aiding unrelated individuals with the expectation of a returned favor. This evolves in stable social groups where "cheaters" are punished. The "tit-for-tat" strategy—starting with cooperation and then mimicking the opponent's last move—is often the most successful.
Social Learning and Culture
Culture is a system of information transfer through social learning or teaching that can alter behavioral phenotypes.
Mate Choice Copying: Female guppies (Poecilia reticulata) will ignore their innate preference for orange males if they observe another female mating with a less colorful male.
Alarm Calls: Young vervet monkeys learn the specific meanings of alarm calls (for leopards, eagles, or snakes) through social confirmation from the group.
Sociobiology: The study of the evolutionary basis of social behavior. E.O. Wilson proposed that human social behaviors are influenced by our genetic makeup, though human behavior remains highly plastic due to our capacity for learning.