Behavioral Ecology

1. Behavioral Ecology • Study of how behavior is controlled, evolves, and enhances survival and reproductive success of organisms. • Behavior is what an organism does and how it does it.

2. Proximate and Ultimate Questions • Proximate questions focus on mechanisms and development of behavior. • They are “how” questions. • For example: How does a bird learn its species song? Or How does a plant know when to produce flowers?

3. Proximate questions • Possible hypotheses that address these “how” questions include: • Males learn their species song by listening to what their father sings and • Flowering in plants is triggered by increasing daylight.

4. Ultimate questions • Are “why” questions. • They ask why natural selection favors the behavior and ultimate hypotheses suggest that the behavior enhances fitness.

5. Ultimate questions • For example: Why do female birds prefer males with brighter plumage? • Or Why do birds look up occasionally when they are feeding?

6. Ultimate questions • Ultimate hypotheses that might address these “why” questions include: • Females prefer males with brighter plumage because such males possess genes that confer disease resistance and • Birds look up to scan for predators, which enhances their survival.

7. Ethology • Field of Behavioral Ecology pioneered by ethologists in middle of 20th century who included Niko Tinbergen, Karl von Frisch and Konrad Lorenz (shared 1973 Nobel Prize).

8. They carried out many well known studies including studies on fixed action patterns and imprinting.

9. Fixed action pattern (FAP) • Fixed Action Pattern is a sequence of behaviors that is essentially unchangeable and once begun is completed. • Tinbergen studied FAP in three-spined sticklebacks. Males have red bellies and defend territories from other males. But they will attack any small unrealistic model fish so long as it has a red belly.

11. Fixed action pattern (FAP) • Red belly is a “releaser” that causes stickleback to initiate its defensive response.

12. Fig 51.4

13. Imprinting • Lorenz carried out famous studies of imprinting behavior in graylag geese. • Young goslings imprint on their mother in first few days of life, follow her and learn basic goose behaviors.

15. However, goslings will imprint on a human substitute (or an object such as a toy truck) if exposed to the correct stimuli (large object that moves away slowly). • Imprinting occurs in a short sensitive period and is irreversible.

16. Fig 51.5

17. Genetic components of behavior • Behavior is affected by both genes and the environment. • In some cases there is variation between individuals in their behavior as a result of differences in environmental influences. • In other cases individuals in population show little variation despite differences in environmental influences. These are innatebehaviors

18. Innate behavior: Kinesis Kinesis: strong change in activity or turning rate in response to stimulus. E.g. Woodlice become more active in dry areas and less in humid areas. Helps to keep them in moist areas and move out of dry.

19. Fig 51.7a

20. Innate behavior: Taxis • Movement towards or away from a stimulus. • Cockroaches demonstrate negative phototaxis (move away from light). • Trout demonstrate positive rheotaxis and face towards the current in a stream.

21. Fig. 51.7b

22. Innate behavior: migratory orientation in blackcaps

23. Innate behavior: migratory orientation in blackcaps • European blackcaps migrate to Africa. • Can assess direction birds choose to migrate using an Emlen funnel. • Birds spend most time in part of funnel that faces in direction they want to migrate.

25. Innate behavior: migratory orientation in blackcaps • Blackcaps from SW Germany migrate in SW direction and those from Hungary in a SE direction.

27. Innate behavior: migratory orientation in blackcaps • Members of two populations crossed and produced offspring. • Offspring orientation tested in Emlen funnel.

28. Mean orientation of offspring south. Strong evidence that there is genetic control of orientation Inner ring Adults. Outer ring Offspring.

29. Environment modifies behavior • Habituation. Loss of responsiveness to stimuli that do not convey useful information (“cry wolf” effect).

30. Environment modifies behavior • Associative learning. Many birds learn quickly that Monarch butterflies taste foul and will avoid them after an initial experience. • Rats will permanently avoid a food if after eating some of it they subsequently become nauseated.

31. Environment modifies behavior • Spatial learning. Many animals modify their behavior depending on the environment they live in. • In stable environments landmarks are useful for navigating.

32. Environment modifies behavior • Sticklebacks modify their behavior with landmark stability. • Fish taken from ponds (where landmarks are more stable) make more use of landmarks than fish taken from streams in lab experiments.

33. Behavioral traits evolve by natural selection • Agelenopis aperta a funnel web spider occurs in both desert and riparian (riverside) woodland. • Desert spiders (which occur in food-poor habitat) are much more aggressive and attack potential prey much more quickly than riverine spiders.

34. 51.19

35. Behavioral traits evolve by natural selection • Differences between spiders persist in the lab and in lab reared offspring so behavioral difference has a genetic basis. • Selective reason for difference appears to be that food and predators more common in riparian habitat. Risk of missing a meal a greater cost for desert spiders than their risk of predation. The reverse is true for riparian spiders.

36. Behavioral traits evolve by natural selection. Drosophila foraging. • Two alleles in a gene for foraging forR and fors. • forR : rover larva moves more than average; fors sitter larva moves less than average.

37. Foraging pathways of individual Drosophila larvae Rover Sitter

38. Behavioral traits evolve by natural selection. Drosophila foraging. • In lab studies in low density populations of Drosophila fors allele increased in frequency. Opposite was true in high density populations. • In low density populations fors individuals did not waste energy traveling long distances for food. In high-density populations forR allele caused larvae to move beyond areas of food depletion.

39. Many other single gene effects found in Drosophila. E.g. Stuck – males don’t dismount after normal 20-minute copulation Coitus interruptus - male copulates for only 10 minutes.

40. Natural selection favors behaviors that increase survival + reproduction • Differences in reproductive success of different genotypes result in evolution. This is natural selection. • Behaviors that increase mating opportunities and survival will enhance reproductive success.

41. We expect natural selection to favor behaviors that enhance survival (e.g. efficient foraging behavior and avoidance of predators) and that results in higher reproductive success (e.g. choosing high quality mates, avoiding cuckoldry)

42. Optimal foraging • A lot of work has been carried out on how organisms maximize their food intake while minimizing their energy expenditure and risk of mortality. • Expectation underlying this work is that organisms will be efficient and forage optimally.

43. Zach’s crow work • Crows feeding on whelks (marine snails) fly up and drop the whelks on rocks to break them. • Height from which a shell is dropped affects its probability of breaking. • Dropping from greater height increases probability of breaking shell, but it costs energy to fly up.

44. Reto Zach studied crows and predicted they would fly to a height that, on average, provided the most food relative to the energy needed to break the shell. • Zach dropped shells from different heights and for each height determined the average number of drops needed to break a shell.

45. Then he calculated total flight height (number of drops x height of each flight) as a measure of the energy needed to break a shell. • Zach predicted a height of 5m would be the optimal flight height. Observed height crows flew to was 5.23, a close match.

46. Fig 51.22

47. Minimizing predation risk while foraging. • There are numerous ways in which organisms attempt to minimize their risk of predation. • These include: avoiding habitats that are the most dangerous, foraging in groups and spending time looking for predators.

48. Many animals group together to avoid predation. • Grouping increases chances a predator will be spotted before it can attack. Grouping also increases time spent foraging as individuals have to scan less often in a group.

49. Experiments by Kenward using a trained Goshawk showed that as flock size increased woodpigeons detected an approaching bird at greater distances.