Chapter 51. Behavioral Ecology. Behavioral Ecology. The scientific observation of animal behavior, what controls it, how it develops, evolves, and contributes to the reproductive success of an organism. Behavioral Ecology.
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Chapter 51 Behavioral Ecology
Behavioral Ecology • The scientific observation of animal behavior, what controls it, how it develops, evolves, and contributes to the reproductive success of an organism.
Behavioral Ecology • Understanding animal behavior is important to conserving endangered species and controlling the spread of infectious diseases.
Animal Behavior • There are two main classes of questions that can be asked about animal behavior: • 1. Those that focus on immediate stimulus and mechanism of behavior. • 2. Those that explore how the behavior contributes to the survival and reproductive success.
What Is Behavior? • It is a phenotype--a product of our genes. • Behavior is everything an animal does, and how it does it. • Behavior can also be learned.
Proximate and Ultimate Questions • The observation of behavior involves proximate and ultimate questions. • Proximate questions focus on the stimulus and what triggers the behavior. • Ultimate questions address the evolutionary significance of a behavior.
Proximate Questions • Again, these focus on the stimulus and what triggers it. • Additionally, it seeks the genetic, physiological, and anatomical mechanisms underlying the behavior. • Most importantly: these are mechanism and development questions.
Ultimate Questions • Address evolutionary significance of behavior. • They are often questions that propose a hypothesis about an observed behavior.
4 Questions For Understanding Behavior • Proximate Questions (mechanism and development): • 1. What is the mechanistic basis for behavior? • 2. How does the development of the animal from the zygote to the mature individual influence behavior?
4 Questions For Understanding Behavior • Ultimate Questions (evolutionary): • 3. What is the evolutionary history of the behavior? • 4. How does the behavior contribute to the survival and reproductive fitness?
Fixed Patterns and Imprinting • These are two behaviors frequently studied by ethologists. • Fixed Action Pattern (FAP) is a sequence of unlearned behaviors that are essentially unchangable. • Once initiated, they are carried to completion. • An FAP is triggered by an external sensory stimulus called a sign stimulus.
Niko Tinbergen • A classic example of sign stimuli and FAP’s: • 3-spined male stickleback fish.
Niko Tinbergen • These fish attack other males invading their nesting area. • The stimulus comes from the red underside of the intruder. • The stickleback won’t attack any fish lacking a red-belly. Females don’t have red bellies.
Niko Tinbergen • The male sticklebacks will attack fake models, unrealistic models, anything as long as some red is present.
Imprinting • Imprinting is a type of behavior that involves both learning and innate components which are generally irreversible.
Imprinting • The sensitive period of imprinting only lasts a limited time, and is the only time where certain behaviors can be learned. • During periods of bonding, young imprint on their parents and learn the basic behaviors of their species. • This is also the period of time where the parents learn the appearance of their offspring.
Imprinting • If bonding doesn’t occur, death of the offspring usually results. • How and on whom do the young know to imprint?
Imprinting • The tendency to respond is innate in the birds. • The outside world provides an imprinting stimulus, something to which the response will be directed.
Konrad Lorenz • Lorenz experimented with geese. • Extensive research shows that behavioral traits are influenced by both genetic and environmental components. Just as much as are the anatomical and physiological traits.
Konrad Lorenz • In fact, Lorenz showed that geese (and other nidifugous birds) imprint on the first moving stimulus they see shortly after their birth. http://www.awakeningpotentials.com/images/imprinting2.jpg
Nature Vs. Nurture • This is not a debate in biology. The question becomes: How do both the genes and the environment influence the development of phenotypes? • Behavior that is developmentally fixed is called innate behavior (nature). • Behavior that is a result of the environment is called learned behavior (nurture).
Studying Nature Vs. Nurture--Movements • Many movements are under genetic influence and are called “directed movements.” • Kinesis is a simple change in activity or turning rate in response to a stimulus.
Kinesis Example: • Sow (pill) bugs survive best in moist environments. • They exhibit kinesis in response to variations in humidity. • They become more active only in dry areas. • They are less active in moist areas.
Kinesis • The sow bugs don’t move toward or away from specific conditions. • Their increased movement in response to a dry condition increases the likelihood they will end up under a moist area. • When they reach a moist area, they slow down, and this increases the likelihood they will stay there.
Taxis • Taxis is the movement toward or away from a stimulus. • Positive-toward. • Negative-away.
Studying Nature Vs. Nurture--Communication • Behavior can be controlled by signals and responses. • The transmission of, reception of, and response to signals constitute communication.
The Types of Animal Signals • There are two main types: • 1. Chemical signals • 2. Auditory signals
Chemical Signals • Chemical signals and pheromones are genetically controlled and elicit a behavior in other animals.
Auditory Signals • Some animals such as birds and insects sing songs. • Others make noises with their body parts. These songs are related to courtship rituals and are under genetic control (nature), learned control (nurture), and/or both.
Natural Selection • Natural selection favors behaviors that increase survival and reproductive success. • This can be observed in nature.
Optimal Foraging • Optimal foraging behavior looks at the process of hunting for food as a compromise between the nutritional benefits of gathering food and the energy costs of obtaining food.
Optimal Foraging • According to this theory, natural selection favors the individuals that utilize a foraging behavior that minimizes energy costs while maximizing energy output.
Optimal Foraging • Example: • The energy cost-benefit of dropping molluscs on the coastal rocks by Northwestern crows.
Sexual Selection • Recall that it is basically natural selection for mating success. Mates are chosen on the basis of their characteristics.
Sexual Selection • Determining the basis of sexual selection in female zebra finches. • Females imprinted on their fathers, and this was demonstrated by experimenting with the young finches.
Sexual Selection • Male zebra finches have a very ornate head compared to female finches. • On the heads of these birds were taped red feathers. • Different nests were examined. • Only males • Males and females • Just females
Sexual Selection • These feathers were taped on before the eyes of the young were opened to determine which sex played a role in mate preference. • The results were compared to control groups of offspring whose parents had no headdresses.
Sexual Selection • When the chicks matured, they were given a variety of mate choices. • Males had no preference at all toward ornamented or non-ornamented females.
Sexual Selection • Females raised by non-adorned parents or females with a headdress, had no preference between ornamented or non-ornamented males.
Sexual Selection • Females raised in families with the male having the red headdress preferred males with heads having headdresses suggesting females imprint on their fathers.
Sexual Selection • These results also suggest that the mate choice selection by females plays a part in the evolution of ornamentation in male zebra finches.
Sexual Selection • There are also forms of male competition for mates. • Male competition for mates is a source of intrasexual competition that can reduce variation. http://image16.webshots.com/16/1/42/94/183414294zHoflW_ph.jpg
Agonistic Behavior • Agonistic behavior, for example, is a ritualistic type of competition that determines which competitors gain access to a resource such as food or mates. • The outcome can be determined by strength, size, or in the form of horns, teeth, etc. • They can be psychological in appearance.
Preservation of Variation • Although the potential for reduced variation is there, there also exists a wide variety of individuals with a lot of behavioral and morphological adaptation.
Preservation of Variation • Despite cases of reduced variation, there are many species that maintain variation. • Isopods that live within sponges are an example.
, , and Isopods • These genetically distinct males live within sponges. • -males defend sponges against other -males. • -males mimic the female morphology and behavior. They get no response from -males and have free access to the harem. • -males live within the harem.
, , and Isopods’ Mating Success • The mating success is dependent on the densities of males and female living within the sponges. • When one female lives in the sponge, the -male fathers most of the offspring. • When there is more than one female, the -male fathers 60% of the offspring. • As the harem size increases, the -male’s reproductive rate increases.
Conclusions • The information demonstrates that the reproductive success among the three different males is equal. • To explain the situation where natural selection fails to exclude any one variation (such as the one with the ,, and isopods), scientists use what is known as game theory.