Animal Behavior - CrashCourse Biology #25
Understanding Animal Behavior
The Nature of Behavior
- Behavior is defined as an action in response to a stimulus, illustrated by the example of a cat responding to the sound of treat bags and its internal hunger.
- Animal behaviors serve essential purposes such as mating, eating, avoiding predators, and raising young; these behaviors are subject to natural selection.
- Beneficial behaviors enhance survival and reproduction but can also include selfless actions that benefit others.
Factors Influencing Behavior
- An animal's behavior is constrained by its morphology (physical structure) and physiology (function), which dictate what actions are possible.
- For instance, cats lack opposable thumbs limiting their ability to open treat bags; similarly, other animals have physical limitations affecting their behavior.
Genetic Underpinnings of Behavior
- Traits related to morphology and physiology are often heritable; thus, natural selection acts on both traits and associated behaviors.
- While some behaviors are genetically coded, others are learned. Natural selection favors brain structures that enable learning.
Exploring Behavioral Questions
Niko Tinbergen's Four Questions
- Ethologist Niko Tinbergen developed four questions aimed at understanding animal behavior: two focus on how a behavior occurs (proximate causes), while two address why it has evolved (ultimate causes).
Proximate Causes
- The first proximate question examines what stimulus triggers a behavior; for example, male Siberian hamsters respond to pheromones released by females ready to mate.
- The second proximate question investigates the animal's bodily response to that stimulus—male hamsters scuttle quickly towards the source of pheromones.
Ultimate Causes
- The first ultimate question explores how a behavior aids survival or reproduction; detecting female pheromones directly enhances reproductive success for male hamsters.
- The second ultimate question considers the evolutionary history behind the behavior—superior pheromone detection leads to greater reproductive success over generations.
The Pioneers of Ethology
Contributions of Key Figures
- Niko Tinbergen was part of a trio with Karl von Frisch and Konrad Lorenz who laid foundational work in ethology, earning them the Nobel Prize in 1973.
Imprinting Studies by Konrad Lorenz
- Lorenz’s experiments with graylag geese demonstrated imprinting—the formation of social bonds where young animals follow any moving object they encounter shortly after hatching.
Observations on Recognition
Nazi Affiliation and Behavioral Studies
Lorenz's Controversial Background
- Lorenz was a member of the Nazi party from 1938 to 1943, which influenced his studies on hybrid geese and "tainted blood."
- He warned that even a small amount of "tainted blood" could affect a "pure-blooded" race, leading to misinterpretations by Nazi leaders regarding his behavioral studies.
Natural Selection and Behavior
Foraging Behavior
- Natural selection influences behaviors related to foraging, where animals optimize energy use while exploiting food sources.
- The alligator snapping turtle exemplifies optimal foraging by using its pink, worm-like tongue to attract fish without expending much energy.
Sexual Selection
- Behaviors associated with mating are shaped by sexual selection; traits that enhance reproductive success become favored.
- Male bower birds collect various objects to attract females, showcasing how elaborate displays can influence mate choice.
Intelligence and Mating Success
Bower Bird Behavior
- Males build intricate bowers and perform dances to impress females; complexity in these behaviors correlates with intelligence.
- Females evaluate multiple bowers before selecting mates, indicating that both physical strength and cognitive abilities play roles in attraction.
Altruism in Animal Behavior
Understanding Altruism
- Some species exhibit altruistic behavior, such as vampire bats sharing food with clan members who did not feed.
- British scientist William Hamilton proposed an equation explaining how natural selection can favor altruism through inclusive fitness.
Inclusive Fitness Concept
- Inclusive fitness expands Darwin's definition of fitness by considering the reproductive success of relatives alongside one's own offspring.