Lecture 32 Notes PDF

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Lecture 32 Notes...

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Lecture 32 12/1/17 Prof. Spilios’s email: [email protected] Prof. Spilios’s Office Hours: Tuesday/Thursday 11:00 AM – noon, Wednesday 12:00 pm – 1:00 pm or by appointment (in SCI301A) S2S Tutors info Chao Wu ([email protected]): Office Hours: Monday 11:45-1:45pm Erica Broderhausen ([email protected]): Office Hours: Wednesday 11:30-1:00pm George Tarantino ([email protected]) Office Hours: Thursday 4-6pm *Office hours occur weekly ~Notes by George Tarantino

Song learning in White Crowned Sparrows How does a White Crowned Sparrow learn it’s species specific song? Classic experiments done by Peter Marler Experimental treatment Raised sparrows in captivity and controlled their auditory environment

A Young White-Crowned Sparrow that was exposed to: White-Crowned Sparrow Song- correctly learned and was able to sing the correct song of its own species Song Sparrow Songs- does not correctly learn the song sparrow’s song and sings a poorly developed song as an adult Songs of both species – correctly learned and was able to sing a perfectly good song of its own species No songs of any kind- was not able to correctly learn and sing a good song of its own species, BUT, its song did have the same general characteristics of a White-Crowned Sparrow song Additionally, some birds were experimentally deafened before sexual maturity- these birds were not able to produce the correct species-typical song.

Conclusions: Song learning is dependent on instinct AND learning Song learning is guided by instinct (some intrinsic mechanism that) … Supporting evidence: When exposed to both its own song and the song of another species, the White-Crowned sparrow sang its own song as an adult. When the bird was not exposed to any songs, as an adult its sang a song with the same general characteristics of the species-typical song. Song learning is ALSO guided by active learning Supporting evidence: In order to correctly sing a perfectly good song as an adult, the bird must have early exposure to its species-specific song and must be able to hear itself to practice BUT WAIT THERE’S MORE In the experiments above, the auditory input was delivered entirely by electronic speaker. If given the chance to have social interaction with male “tutors” of another species, the white-crowned sparrow can correctly learn the song of another species and will even do so in preference to their own song. It was previously thought that the first 50 days of a birds life was a critical period to learn a song but if you add social interaction a bird can learn songs after this 50 days How does a song develop? Canaries reared in the presence of other singing adult canaries learn to very closely imitate the adults song. Development of the crystalized (final) song takes about 6-8 months. However, injection of testosterone at 2 months of age induced the development of crystalized song in just one week.

Canary reared in isolation

A canary reared in isolation develops a unique song, but with the same general characteristics of a canary song! (We saw the same thing with the White-crowned sparrow reared in isolation) What kind of songs can a canary learn? In a typical canary song, the canary will repeat the same note several times before singing a new note. So, can canaries sing other types of songs? When canaries have early exposure to an artificial, computer generated song in which no note is repeated, will the canary sing a similar song?

At first, the canary imitates the artificial song pretty well, with the best imitation occurring at 200 days old. However, as the canary gets older it sings a song that is more like a typical canary song (with repeating notes) Further supports the conclusion that song learning is not simply memorization!!

BUT WAIT THERE’S MORE There is great variation among species regarding song learning Song learning like the type described above occurs in about 4000 species of birds. Most other birds (~1000 species) have innate songs that do not require early auditory exposure. Song dialects- Members of the same species in different geographical regions can have slightly different songs, but with the same general characteristics

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How does behavior evolve? Like any other trait! Natural selection and evolution. Genes encode for behavior too! Behavioral ecology Starts with a default assumption that animals are well-adapted to their specific ecological and social environment The intersection between ecology, evolution and behavior Comparative analysis- hypotheses are tested by making comparisons between species Emphasis on quantitative models Cost/benefit analysis Basic premise- every animal has a limited amount of time and energy available, and time and energy spent doing one activity is not spent doing another activity Any behavior has a cost Energy cost Opportunity cost Risk We expect animals to behave in a way that minimizes cost and maximizes gains/benefits

Optimal foraging Example- Picking blueberries Picking every blueberry on a bush is not ideal because some blueberries might be harder to get—we can maximize the berries we get and minimize the energy

spent if we just get the easy ones on a bush and then move to the next bush and get the easy ones on that bush, etc. As we spend more time at a bush, we expect our return to diminish (at first we get a lot of berries because we go after the easy ones, but as we spend more time at the bush the berries get harder to get and the rate at which we get berries decreases. (Law of Diminishing Returns) What if the next bush is really far away? Probably going to pick more blueberries from the first bush Optimal foraging Assumption that an animall that is better at acquiring energy from the environment will be better at survival Central place foraging - collection and delivery of food to young in nest How many prey items should a starling collect before returning to its nest to maximize returns (worms collected) and minimize effort? More time they spend getting prey the returns diminish How should a starling change its behavior in relation to travel time? We can answer these questions using Marginal Value Theorem The starling should return home when its instantaneous rate of change equals the average rate of gain (when getting one more worm would no longer be beneficial).

What if we change the travel time? Experiment- mealworms delivered by researcher in accordance to the law of diminishing returns (the longer the sparrow stayed the less frequently the researcher gave it worms) Also manipulated the travel time Experimental results matched the proposed model – If travel time is longer, the ideal number of worms for a starling to get increases

Ideal # = 6...