2. Biology 441: 9/17/07 Last time  Types of questions (Proximate vs. Ultimate)  Behavioral research methods Today  Behavioral methods cont’d  Crickets  Infanticide discussion Next time  Development of Behavior [ http://research.amnh.org/~krussell/professional/teaching.htm]

3. Behavioral Research Methods 2. Experimental Methods  Manipulating something (independent variable) and measuring its affect on something else (dependent variable) while holding other factors constant Best suited for lab situations; psychology

4. Behavioral Research Methods 2. Experimental Methods  Example: Method of isolation Bird song in white-crowned sparrows

5. Behavioral Research Methods 2. Experimental Methods  Problems with laboratory studies Difficult to generalize Artificial situation affects behavior

6. Behavioral Research Methods 2. Experimental Methods  Example of field study Wasp nest location & landmarks (Tinbergen)

7. Tinbergen and beewolf wasps Wasp hunts bees to provision their young Young are reared in burrows Burrows occur in groups Burrows entrances are buried when the wasp leaves to hunt Wasps can relocate their nests quickly Example:

8. Observation Wasps were marked to allow recognition of individuals Wasps returned to same nest and only constructed one nest Wasps would circle their nest before departing to hunt Example:

9. Hypothesis (possible explanation; educated guess) Tinbergen’s hypothesis - wasps used landmarks to locate their nests Example:

10. Experiment Tinbergen cleared possible landmarks from around the nest When the wasps returned, they circled but could not locate the nest site Does this prove Tinbergen’s hypothesis correct? Can this result be explained in other ways? Example:

11. Experiment (additional experiment) Tinbergen shifted landmarks from around the nest to a site close by He wanted to see if the wasps could be trained to the landmarks When the wasps returned, they landed within the landmarks Example:

12. Landmarks (pinecones) around nest Landmarks shifted to new site

13. Experiment (additional experiment) Tinbergen shifted landmarks from around the nest to a site close by He wanted to see if the wasps could be trained to the landmarks When the wasps returned, they landed within the landmarks Does this prove Tinbergen’s hypothesis correct? Can this result be explained in other ways? Example:

14. Behavioral Research Methods 2. Experimental Methods  Problems with field studies Lack of control; inability to hold certain variables constant

15. Behavioral Research Methods 3. Correlational Methods  Measurable changes in animals behavior that are predictable from some other variable that we can measure

16. Behavioral Research Methods 3. Correlational Methods  Measurable changes in animals behavior that are predictable from some other variable that we can measure E.g., temperature and activity

17. Behavioral Research Methods 3. Correlational Methods  Problem: cannot infer causation

18. Behavioral Research Methods 3. Correlational Methods  Problem: cannot infer causation  Solution? Manipulate potential causal factor (experimental)

19. Behavioral Research Methods 3. Correlational Methods  Problem: cannot infer causation  Solution? Manipulate potential causal factor Not possible for study of human behavior

20. Behavioral Research Methods 4. The Comparative Method  Comparisons of behavior within species or between species Idea that animals are optimally adapted to their environment

21. Behavioral Research Methods 4. The Comparative Method  Comparisons among living species Different strategies in different habitats

22. Behavioral Research Methods 4. The Comparative Method  Comparisons among living species Different strategies in different habitats Different strategies in same habitat  E.g., Agelenopsis aperta & anti-predator behavior

23. Behavioral Research Methods 4. The Comparative Method  Comparisons among living species Different strategies in different habitats Different strategies in same habitat Related species: differences in life styles related to habitat  E.g. Kittiwake vs. black-headed gulls

24. Behavioral Research Methods 4. The Comparative Method  Fossils (ancestors) Clues about behavior  Teeth marks, aggregation, nesting, etc.

25. Behavioral Research Methods 5. Cost-Benefit Analysis  Behavior is examined in terms of cost to animal vs. gain to animal Assumption that animals behave to maximize gains and minimize costs

26. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls

27. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls Observations:  Gulls remove eggshells from nest 1 hour after hatching Cost? Energy/time spent moving shells; leaving the nest (predation risk)

28. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls Observations:  Gulls remove eggshells from nest 1 hour after hatching Cost? Energy/time spent moving shells; leaving the nest (predation risk) Benefit?

29. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls More information:  Nest in open  Numerous nest predators  Nests are unguarded while parents forage  Cryptic nest, offspring, and eggs  Inside of egg is white Hypothesis?

30. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls Hypothesis? (ultimate cause)  Removal of egg shells decreases likelihood of predation Test?

31. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls Hypothesis? (ultimate cause)  Removal of egg shells decreases likelihood of predation Test?  Establish artificial nests  Place eggshells at 15 cm, 100cm and 200cm

32. Behavioral Research Methods 5. Cost-Benefit Analysis  Example: Tinbergen (again) and black-headed gulls  Steps to address ultimate causes Question: Why had black-headed gulls evolved a special response to eggshells in their nest Hypothesis: Eggshell removal had become common because it helped gulls conceal their offspring Prediction: Predators would use eggshell as a cue for finding eggs Experiment: Find out what predators did Conclusion: Match data to hypothesis

33. Results: Do these data support the idea that eggshell removal is reproductively advantageous?

34. Black-headed Gulls Experimental method  Nests with eggshells near them more likely to predated Comparative method  The Kittiwake ignores shells; has no nest predators

35. Black-headed Gulls Next Question:  Why wait 1 hour to remove shells? Cost: increased likelihood of predation Benefit?

36. Black-headed Gulls Next Question:  Why wait 1 hour to remove shells? Cost: increased likelihood of predation Benefit? More info:  Chicks easier to eat when plumage wet  Cannibalism likely (neighbors)

37. Black-headed Gulls Next Question:  Why wait 1 hour to remove shells? Cost: increased likelihood of predation Benefit? Avoid predation by neighbors if wait

38. Black-headed Gulls Next Question:  Why wait 1 hour to remove shells? Cost: increased likelihood of predation Benefit? Avoid predation by neighbors if wait Comparative Method:  Oystercatcher chicks not in danger of predation by neighbors  Parents remove egg shell immediately

39. Behavioral Research Methods SUMMARY  1. Observation method  2. Experimental method  3. Correlational method  4. Comparative method  5. Cost-benefit analysis

40. Discussion Questions Which of the two articles is most persuasive, and why? How does progress in science arise from controversies of this sort? Can you link the opposing interpretations of these two studies to our discussion of ultimate and proximate causation of behavior?