Transcript Topic 1
Biology 484 – Ethology Topic 1 – An Evolutionary Approach to Animal Behavior What is Ethology? • Ethology is the scientific and objective study of animal behavior • Often, ethology has a focus on behavior under natural conditions • However, laboratory based studies of behavior are also very important for what is called “proximate understanding” of behavior • Critical in the study of ethology is the idea that behavior is an evolutionarily adaptive trait An example of a laboratory based study that has “natural world” relevance: Isopod Behavioral Responses to Moisture Douglas Spaulding – (1841-1877) • biologist who first described the idea of “imprinting” • overlooked for many decades by scientists because his writings were published in rather obscure journals • his ideas were further developed by Heinroth and Lorenz Oskar Heinroth (1871-1945) • German biologist who was the first to apply methods of comparative morphology to animal behaviour • His extensive studies of behavior in the ducks and geese showed that instinctive behavior patterns correlated with taxonomic relationships determined on the basis of morphological features. •He also rediscovered the phenomenon of imprinting, reported in the 19th century by Douglas Spalding Konrad Lorenz (1903-1989) Received 1973 Nobel Prize in Physiology (along with Tinbergen and vonFrisch) for their foundation work in the field of ethology • Lorenz studied instinctive behavior in animals. • The primary animals he worked with were greylag geese and jackdaws • While working with geese, he rediscovered the principle of imprinting Karl vonFrisch (1886 – 1982) • His work centered on investigations of the sensory perceptions of the honey bee. • He was the first to discern and translate the meaning of the honeybee “waggle dance.” • His theory was disputed by other scientists and greeted with skepticism at the time. Niko Tinbergen (1907 – 1988) well known for originating the four “questions” he believed should be asked about any animal behavior relating to: Causation, Ontogeny, Phylogeny, Adaptation These shall be a primary focus in this chapter of our text. A major body of Tinbergen's research focused on what he termed Supernormal Stimuli. This was the concept that one could build an artificial object which was a stronger stimulus or releaser for an instinct than the object for which the instinct originally evolved. Tinbergen observed that sticklebacks perform an elaborate mating ritual that is carried out the same way each time: 1) First the male stakes out a little area in its environment which becomes its territory 2) The male stickleback then digs a little hole (in loose detritus), shoveling material with his snout until a hole is constructed 3) He gathers stringy pieces of algae, coats them with a sticky substance secreted from his kidneys, and piles the algae in the pit, forming a little mound 4) Finally, the male stickleback wiggles through the mount, leaving a tunnel B.F. Skinner (1904 – 1990) • invented the operant conditioning chamber • developed and innovated his own philosophy of science called radical behaviorism • founded his own school of experimental research psychology….. the experimental analysis of behavior from a psychology perspective The basic design of the “Skinnerian Operant Chamber”. The advantages of this device are many and have significantly affected both psychological and biological studies of behavior. Tinbergen’s four “questions” further expanded and developed by Holekamp and Sherman describe different perspectives on how to examine behavior. Kay Holekamp – Researcher at Michigan State University Paul Sherman – Researcher at Cornell University The monogamous prairie vole • the Prairie Vole (Microtus ochrogaster) is a mouse-like mammal that displays a rather rare type of reproductive behavior for rodents • this species of vole is monogamous… meaning it will mate and bond exclusively with a single other vole and remain bonded for life. • the vast majority of voles (and rodents in general) are polygynous (have multiple mating partners) The interesting aspect of this rather rare behavior is why does this behavior arise? Many answers we shall see combine information and techniques from the fields of neurobiology and endocrinology to discern answers to ethological questions. • The Ventral Pallidum is a structure within the basal ganglia of the brain. • The Ventral Pallidum is classified as an output nucleus whose fibers project to thalamic nuclei, such as the ventral anterior nucleus, the ventrolateral nucleus, and the medial dorsal nucleus. • The Ventral Pallidum is a component of the limbic loop of the basal ganglia, a pathway involved in the regulation of motivation, behavior, and emotions. It is involved in drug addiction. The brain of the prairie vole is a complex, highly organized machine The ventral pallium region of the Prairie Vole brain differs from most other rodent brains in that there are very high numbers of receptors for the hormone, vassopressin (or sometimes called anti-diuretic hormone (ADH). This region of the brain is associated with the reward centers in our brain. Each time the male Prarie Vole mates with a female it stimulates the release of vasopressin, which floods and stimulates the brain region causing pleasure and encourages the pair bond to form. Most other rodents have significantly lower numbers of these receptors in this region of the brain. • Neuroendocrinology is the study of the extensive interactions between the nervous system and the endocrine system. • Especially important to neuroendocrinology are the biological features of the cells and how they functionally communicate. • Neuroendocrinology originally arose from the recognition that the brain, especially the hypothalamus, controls secretion of pituitary gland hormones. • Currently, neuroendocrinology has expanded to investigate all manner of interconnections of the endocrine and nervous systems. A gene that affects male pairing behavior in the prairie vole In a study where Prarie Vole males were genetically altered to have MORE of the gene responsible for producing the receptor proteins for vassopressin, would spend MORE TIME with the female if these added genes were in the ventral pallidum compared to an alternative brain region (CP = caudate putamen) or if an alternative gene were inserted. How are phylogenetic trees constructed and what do they mean? Suggests which species are most closely related Suggests which species are more closely related to a recent ancestor Common features used in phylogenetic trees include: Anatomy Physiological Features Behavior Molecular Relatedness The evolutionary relationships of the prairie vole and six of its relatives The possible history behind monogamy in the prairie vole Potentially, the development of monogamy in the Prairie Vole may be a product of a multitude of slight behavior shifts over time. Testing the hypothesis that monogamy in prairie voles is linked to a specific gene In this experiment, male MEADOW VOLES (normally polygynous) are genetically altered to express higher more of the gene that produces the protein receptors for vasopressin, again, specifically in the ventral pallidum. The males show considerably more time spent “huddling” with females if they are genetically altered than if they are control males. Charles Darwin, shortly after returning from his around-the-world voyage on the Beagle Darwin’s ideas of evolution greatly influence the studies in ethology. The aspects of Darwin’s theory of evolution and the role that change plays in evolution that are especially valuable to ethology inlcuide: • Variation • Heredity and • Differences in reproductive success Charles Darwin’s study A variable species Ladybugs (Harmonia axyridis) can exhibit a wide array of variation in heritable features. Natural selection Darwin’s idea of natural selection is especially well suited for coupling with genetic aspects of heritability. If one heritable feature is favored for a given environment, it will tend to proliferate whereas other forms will be less favored. A band of Hanuman langur females and their offspring Natural selection is the likely reason for the fighting behavior seen in males as they try to monopolize access to female mating partners. Male langurs commit infanticide Infanticide is also a behavior that may have been selected for in an effort to bring females more quickly back into estrus. Infanticide by a male lion Although it is still unclear if infanticide brings a female langur back into estrus faster or if there are other potential explanations for the behavior, it has been shown in research by Hrdy (1977) & Sommer (1994) that lion males who engage in infanticide end up siring a larger number of offspring than males that do not. An evolved response to the risk of infanticide Females may also display infanticide. Here is a male who is guarding fertilized eggs from FEMALES who wish to replace the egg clutch with her own eggs. Conclusions from Topic 1: • Please be aware of the rich role that history and historical figures play in the development of ethology as a science. • Please know and understand the importance of the questions posed by Tinbergen and how they have shaped ethological research. • Understand the importance of Darwin and how his work has been significant in the study of ethology. • Know and understand the examples of sexual and reproductive behaviors described and how they show some of the rich variation that is seen in the study of ethology.