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Behavioral Ecology

Behavioral Ecology

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Behavioral Ecology

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  1. Behavioral Ecology Chapter 32

  2. Animal Behavior • Definition: Actions of an animal in response to stimuli. • Nervous and Endocrine systems play important role by secreting hormones or neurotransmitters.

  3. Genes and Behavior • Some variations in behavior have a genetic basis • Arnold showed that garter snakes’ taste for slugs has genetic basis • Costal garter snake – banana slug • Inland garter snake – tadpoles and fish • Newborns – only ate species specific food • Hybrids –

  4. Hormones and Behavior • In voles, hormone oxytocin affects pair bonding • When hormone is blocked, pair-bonded females dump their partners • Brains of monogamous vole species have more oxytocin and ADH receptors

  5. Instinctive Behavior • Performed without learning experience • Usually triggered by simple sign stimuli • Response is a stereotyped motor program • FIXED

  6. Learned Behavior • Responses change with experiences • Imprinting • Time dependent form of learning • Triggered by exposure to a simple sign stimulus • Ex: Sound of cars

  7. Bird Song: Instinct + Learning • Male birds instinctively recognize a basic song • 10 to 50 days after hatching, a bird learns his particular regional variation from others around him • Birds in soundproof chambers never pick up the other songs.

  8. Adaptive Behavior • Defined as: Behavior that helps an individual propagate it’s own genes. • Gene frequency will be maintained or will increase in successive generations

  9. Selfish, Altruistic, and Social Behavior • Selfish behavior promotes an individual’s genes at the expense of others • Altruistic behavior helps others at the expense of the altruist; may be adaptive under certain circumstances • Social behavior – interdependent interactions among individuals • Social sacrifice -

  10. Communication Signals • Intraspecific signals evolve only if they benefit both species involved. (ex poison ivy ) • Types of signals Pheromones Tactile signals Visual signals Acoustical signals

  11. Pheromones • Chemical signals between members of same species • diffuse through air or water • Signaling pheromones • Induce immediate response

  12. Tactile Display • Signaler and receiver communicate by contact • Honeybee dance language food close food distant

  13. Visual Displays • Important in dominance hierarchies • Baring of teeth by baboon communicates threat • Play bow in wolves solicits play behavior

  14. Acoustical Signals • Sounds used in communication • Lots of examples: --Dog barking --Bird chirping --Elephants --Whales

  15. Signal Variation • Some signals never vary • Zebra ears flat on head always = HOSTILE • Composite signals combine information encoded in more than one cue • Zebra with ears flat on head and mouth wide open = VERY HOSTILE • Signals vary based on context • Lion roar = Threat or trying to contact others

  16. Sexual Selection • Choosiness in selecting a mate • Success is measured by number of offspring produced

  17. Reproductive Strategy MALES FEMALES Produce large, energetically expensive eggs Often provide parental care Reproductive success increases by increasing quality of mates – NOT number of mates • Produce energetically inexpensive sperm • Often provide no parental care • Often maximize reproductive success by mating with as many females as possible

  18. Choosy Females • Female choice can dictate rules of male competition and shape male behavior • Selects for males that appeal to females • Male sage grouse • Male hangingflies offer gifts • Male fiddler crabs wave enormous claws

  19. Male Contests • Females of some species cluster in groups • Males may fight one another for access to females • Selects for: Strength and aggressiveness.

  20. Parenting Behavior • Enhancing survival of offspring increases parents’ reproductive success • Parental behavior comes at a cost:

  21. Benefits of Social Living • Improved detection or repulsion of enemies • Cooperative hunters probably live together to enjoy other benefits (shared care for their young)

  22. Dominance Hierarchy • Some individuals accept subordinate status • Higher ranked members have higher reproductive success than subordinates • So why stay if you are ranked low?

  23. Costs of Social Living • Increased competition for food, mates, and other limiting resources • Attractive to preditors • Increased vulnerability to disease and parasitism • Risk of exploitation by other group members

  24. Hormones and Bonding in Humans • Autistic children • Can’t form normal social relationships • Have lower oxytocin levels • Oxytocin is released in response to • Nursing – “cuddle hormone”

  25. Population Ecology Chapter 28

  26. The Human Touch • Polynesians settled a fertile island about A.D. 350 • By 1400, population soared, exhausting natural resources • By the 1700s, only a few hundred survivors and no resources remained

  27. Population Demographics Population size Number of individuals that make up the gene pool. • Age structure Number of individuals in each age category. • Reproductive base Individuals that are able to reproduce.

  28. Population Demographics cont. • Population density Number of individuals in a specific area. • Population distribution How individuals are dispersed.

  29. Density and Distribution • Crude density information is more useful if combined with distribution data clumped nearly uniform random

  30. Zero Population Growth • Interval in which number of births is balanced by number of deaths • Assume no change as a result of migration • Population size remains stable

  31. Exponential Growth • Population size grows by increasing increments • The larger the population, the more individuals reproduce • All populations grow like this if death rate is lower than birth rate

  32. Limiting Factors • Any essential resource that is in short supply • All limiting factors acting on a population dictate sustainable population size

  33. Carrying Capacity • Definition: The maximum number of individules of a species that an environment can sustain • Logistic growth occurs when population size is limited by carrying capacity initial carrying capacity new carrying capacity

  34. Overshooting Capacity • Population may temporarily increase above carrying capacity • Overshoot is usually followed by a crash; dramatic increase in deaths Reindeer on St. Matthew’s Island

  35. Survivorship Curves • Type I populations:

  36. Survivorship Curves • Type II populations constant death rate

  37. Survivorship Curves • Type III populations: High death rate for young

  38. Human Survivorship

  39. Human Population Growth • Population exceeds 6.6 billion • Rates of increase vary among countries • Average annual increase is 1.3% • By 2050: 8.9 billion • Population continues to increase exponentially

  40. Population Growth ThroughoutHistory

  41. Skyrocketing Growth • Humans expanded into new habitats and climates • Agriculture and fossil fuels increased carrying capacity • Hygiene and medicine neutralize density-dependent controls

  42. Environmental Impacts • United States has 4.6% of world’s population • Produces 21% of goods • Consumes 25% of nonrenewable resources • Generates 25% of world pollution and trash • India has 15% of world’s population • Produces 1% of goods • Uses 3% of nonrenewable resources • Generates 3% of trash and waste