Vocal memes in natural popultaions of chickadees: why do some memes persist and others go extinct?

1. Vocal memes in natural popultaions of chickadees: why do some memes persist and others go extinct? by Myron C. Baker and David E. Gammon

2. The black-capped chickadee(Poecile atricapillus)

3. The Basics • 8 year study • Data obtained from 3 different regions near Fort Collins, CO • Studied “gargle call” (nonsong vocalization) in subjects • Gargle calls vary in acoustic form among populations so essentially they are different memes • Looked at relationship between failed memes and core memes

4. Data collection • Individuals trapped and recaptured each autumn/winter season for 8 consecutive seasons • “gargle calls” collected using sonograph machine and displayed as sound spectrographs

5. Example of a sound spectrograph of a core meme

6. Experiment 1 • Hypothesis: Core memes are more likely to be shared with other individuals than failed memes. • Looked at proportion of individuals expressing the same meme in each population • Results: Sharing of core memes was 4 to 6 times greater than the sharing of failed memes • Each population showed a significant difference in the sharing of core memes and the sharing of failed memes

7. Figure 3. Proportions of chickadees sharing core and failed gargle memes in three populations. In all three populations, sharing was significantly greater for core memes than for failed memes.

8. Experiment 2 • Hypothesis: Core memes are more likely than failed memes to be heard, and encountered in agnostic contests, by an average bird during the course of daily activities. • Looked at the frequency of occurrence of 30 core memes and 35 failed memes • Results: Core memes were expressed significantly more often than failed memes in each popultaion

9. Figure 4. Proportions of core and failed gargle memes expressed by chickadees in three populations. In all three populations, core memes were expressed significantly more often than were failed memes. Data are per core meme and per failed meme. Thus, for example, in the Lee Martinez Park (ML) population, a given core meme represented about 9% of the memes expressed and a given failed meme represented a little less than 2% of the memes expressed.

10. Experiment 3 • Failed memes were found to usually be a result of a bird that has left the population, or a “failed bird” (which is why failed memes only lasted 1-2 seasons) • Hypothesis: Core birds and failed birds differ in body size • Results: Core birds were found to be in better condition than failed birds (in terms of having larger body masses), however the overall sizes of the birds did not differ

11. Experiment 4 • Hypothesis: Core birds and failed birds differ in age. • Evaluated each chickadee’s plumage to determine relative age. • Results: 61% of failed birds were classified as “young” and 70% of core birds were classified as “old”

12. Conclusions • Core memes are more likely to be shared with other individuals than failed memes. • Core memes are more likely than failed memes to be heard, and encountered in agnostic contests, by an average bird during the course of daily activities. • Core birds and failed birds do not differ in body size, but possibly in overall condition. • Failed birds and core birds differ in age.

13. Clips • Genes and Memes • Black-capped chickadee

14. Questions • 1. Which type of meme persisted throughout the study? Core memes or failed memes? • 2. Which memes were associated with birds that left the popultaion? • 3. Failed memes typically lasted how many seasons? • A) 0 B) 1-2 C) 3-4 D) 5 or more