Unit I: Individual Ecology

1. Unit I: Individual Ecology A. The Earth�s Physical Environments and World Vegetation B. Physiological (functional) ecology of plants and animals C. Behavioral ecology of animals

2. I.C. Behavioral Ecology Definition: How an individual animal�s behavior interacts with its environment to affect its survival and reproduction. Foraging ecology (also falls under physiological ecology, e.g., energy acquisition) Territoriality Mating systems

3. Feeding & foraging ecology Feeding = the physiological processes related to being an autotroph or a heterotroph (getting energy & nutrients etc.); Foraging = the behavioral process of finding food and feeding (a field of behavioral ecology)--mostly applies to heterotrophs!

4. Needs of all living organisms=Benefits of foraging 1. energy measured in calories for metabolism, to store for growth, migration, reproduction (producing eggs, offspring, finding and defending mates), competitive ability, escaping predators. 2. water 3. nutrients MACRO: protein or nitrogen for enzymes, tissue etc.; carbohydrates and lipids for energy and various functions ; MICRO: vitamins, minerals (P,K) trace elements-- again depends on the goal (maintenance v growth v reproduction)

5. Costs of feeding/foraging Animals in particular: Choices are necessary! 1. ALLOCATION: time to forage, when time is limited and could be spent on other things 2. Chemicals, toxins & impediments to digestion: other living beings don't want to be eaten! 3. danger and damage again, things don't want to be eaten; foragers are exposed to predation while foraging.

6. Principle of Allocation First law of Ecology (Barry Commoner) NO FREE LUNCH For every benefit there is a cost All resources or options have limits Use or investment in one option comes at the expense of another option =TRADE OFF

7. Formal definitions: Principle of Allocation Definition: All life functions cannot be simultaneously maximized (i.e., all of life�s needs cannot be maximally satisfied.) Trade-offs are necessary because of the principle of allocation Definition: (Webster�s dictionary) �an exchange, especially giving up of one benefit, advantage, etc. in order to gain another regarded as more desirable.�

8. Trade offs in ecology are part of a �cost/benefit� approach In an ecological context, trade-offs arise from conflicting demands and limits, and costs associated with different benefits. An organism has the choice of exchanging one benefit for another, given changing conditions that make one choice more beneficial than another under those conditions. A Cost:Benefit approach is used in most fields of ecology and evolutionary biology

9. Applying the Principle of Allocation and a Cost:Benefit approach to behavior UC Davis student faces these limits: 24 hours/day; $xxx in bank account Time spent studying EVE 101 means less time studying CHEM 118, sleeping, or going to a movie (choice of important activities) Studying EVE 101 is obviously the most beneficial of those activities, so you take time away from them to learn about ecology

10. Egs: Principle of allocation and tradeoffs Plants: carbon fixed can be allocated to: leaves (shoots) in getting energy from sun v. roots which collect water, nutrients v. flowers & seeds (reproduction); Animals: energy obtained can be allocated to: time to forage, feed & digest, v. finding mates, v. caring for young, v. escaping predators.

11. Cost:Benefit thinking Profit or net benefit = �Gross� benefit minus the cost Do plants and animals make economically �rational� = profitable decisions in pursuing their goals of survival and reproduction This �choosing� does not have to be a conscious decision To �choose�= two possible (potential) options and only one option occurs. A plant can �choose� to open or close its stomata for example.

12. Maximization & optimization Maximizing profit Most benefit for least cost = maximizing fitness (survival, growth or reproduction) �Optimal� only means maximizing something under the possible set of conditions in ecology & evolution �Optimal� does not mean perfect or best hypothetical solution

13. Decisions and choices In foraging ecology of animals, the big question is: Do animals actually choose the food items they ingest? Do they make profitable decisions? Or, are they feeding robots that just eat anything they encounter, given a list of things they can capture and eat? We can predict an �optimal� diet (that maximizes something) and then test to see if that�s what animals actually do.

14. Hypothesis testing in ecology NULL HYPOTHESIS = Animals consume acceptable food types in proportion to the rate at which the forager encounters them (NO CHOICE) ALTERNATIVE HYPOTHESIS = Animals select available food types to maximize profit (benefit minus cost) therefore foragers choose which of the encountered food types to consume or to skip.

15. Building models to test hypotheses Job of a scientist is not to describe reality Job of a scientist is to discover the simplest necessary explanations for reality Principle of parsimony; Occam�s razor Build models that contain fundamental properties of whatever is being studied and simplifying assumptions Model then generates predictions that can be tests with observations Collection of data tests both assumptions and predictions: Iteration produces the simplest explanations of observed phenomena

16. Optimal Foraging Theory Simplest model Ch. 6.3, p 149 Fundamental properties and assumptions of the simplest model: GOAL: Maximize Energy/Time (or effort) Currency = energy and time only to start YEILD = E/T per daily foraging bout

17. Examples of foragers and their choices

18. Examples of foragers and their choices

19. Examples of foragers and their choices

20. Examples of foragers and their choices

21. Forager has choice of food types that differ in E/T

22. EG: gull foraging

23. Assumption 1:Forager ranks prey according to E/T

24. Assumption 2: Random searchForager encounters prey in the proportion available

25. Assumption 2: Random search�Search time� depends on the density of prey and is independent of type of prey

26. TS = 1 sec to find the next preyCS = 0.1 kcal/sec in search costs

27. Putting together the model

28. Crank the model to make predictions about the forager�s diet

29. Crank the model to make predictions about the forager�s diet

30. First general prediction Whether a food item is selected and eaten depends on: the abundance pi of BETTER (higher ranked) items (ei/ti > e/t) NOT on its own abundance This prediction is counter-intuitive Why not take the most common item when encountering it??

31. Change conditions to make more predictions about the forager�s diet

32. Second general prediction When overall food density increases (N gets bigger, pi stays the same): lower ranked) items (ei/ti > e/t) are dropped from the diet even if they were acceptable before This prediction is counter-intuitive As food becomes more available, foragers get more selective

33. Tests of optimal foraging theory Great tit Parus major Choice of large and small meal worms on a conveyor belt

34. Tests of optimal foraging theory Great tit Parus major Choice of large and small meal worms on a conveyor belt Conveyor belt ran at 2 different speeds for high and low �density�

35. Tests of optimal foraging theory Bluegill Sunfish Lepomis macrochirus Choice of large, medium, and small crustaceans in an aquarium

36. Tests of optimal foraging theory Bluegill Sunfish Prediction that they take less profitable prey (small) in lower proportions than they encounter is upheld But not perfectly

37. Tests of optimal foraging in sunfish

38. Why don�t the data fit the predictions perfectly? Modelling is not a useful approach to studying reality because it�s �unrealistic� Real measurements always involve some error of some kind Something in the model is not exactly correct Assumptions? Fundamental premises?

39. Empirical tests of theory test both the assumptions and predictions of a model Is energy the correct or only currency to maximize? Do foragers search randomly? Do foragers know all the parameters of the model without testing, such as energy of food, handling time, density etc? Are conditions static with time, or is variability to be expected?

40. Variation in available food is to be expected

41. Response to variability in resources

42. Some foragers seek multiple goalsor multi-task

43. Energy maximizer v foraging time minimizerUnder nutrient constraints

44. Some foragers seek multiple goalsor multi-task cont

45. Some foragers travel to forage or forage for different foods in different places

46. Some foragers don�t travel at all

47. Sit & wait vs searching foragers:Eremias lizards in the Kalahari