Song type matching as threat signal in hierarchical animal communication

1. Song type matching as threat signal in hierarchical animal communication Eric Spilker, Elysha Trigg, Lyndsey Ulrich http://ucsantacruz.ucnrs.org/?page_id=1515

2. Authors Michael Beecher CalgarAkcay http://faculty.washington.edu/beecher/ http://evrimcaliskanlari.org//

3. S Elizabeth Campbell Mari E. Tom http://commons.wikimedia.org/wiki/File:Song_Sparrow-27527-2.jpg

4. Background Song Sparrows- Melospizamelodia • Very territorial-aggressive when it comes to other males intruding on territory • Found in open brushy habitat • Mostly monogamous, occasional polygamous • Monomorphic species • Communicate through body language and song

5. Previous Research

6. “The Big Question” Will Song birds who continue to type match respond more aggressively than song birds who switched off or stopped singing?

7. Material and Methods: sciencedaily.com

8. a) Subjects and study population • 48 males • Discovery Park, Seattle • Solid-state recorder with shotgun microphone • Subjects’ territory boundaries based on obs. of singing posts Hiltonpond.org Commons.wikimedia.org Therichsound.com Synthtopia.com

9. b) Stimuli • Subject’s own repertoire • Looped recording of ~3 seconds song with 7 seconds silent period frequency time

10. c) Design and equipment

11. c) Design and equipment: boundary playback Tweet Tweet! 2 mins, repeat once if necessary

12. c) Design and equipment: center playback 15 mins, or until subject attacks mount

13. d) Response measures • Separate for center and boundary playbacks • Center playback: time spent w/in 1m; latency of first approach, attacks • Both playbacks: # loud songs; # soft songs; wing waves; flights; # song types (and switching frequency), # type matches

14. d) Response measures- matching • Subjects classified as: • 1) “Early matchers” (EM)- matched at boundary and continued matching • 2) “Non-matchers”(NM)- never matched or matched late in the escalation phase • 3) “Off-switchers”(OS)- matched at boundary phase but ceased matching/singing afterwards

15. d) Response measures: soft song, wing waves • http://www.youtube.com/watch?v=9ynqMTKs_Fc

16. d) Response measures: attack • http://www.youtube.com/watch?v=4wgmqNvofW0

17. Wikimedia.org RESULTS

18. Results: 1) Does early type-matching predict attack? • YES! EM- 88.2% ; NM- 52.2% ; OS- 50% (X2=6.45, p=0.04) –Chi square • -EM also had highest aggression scores (F=5.81, p= 0.006) --ANOVA

19. Results: What signals are predictive of attack? • Only rates of soft song (F=11.96, p=0.001) and rates of wing waves were significant (F=6.41, p=0.015)—Discriminate function analyses- signalling variables from center playback as an independent variable and attack/no attack as classification variable • Rates of loud songs and switching rates were similar for attackers and non-attackers

20. Results: Are the above signals that are shown to be predictive of attack associated with early type matching? • For wing waves, YES! (x2=6.60, p=0.04) • For soft song, NO (x2=1.70, p=0.43) Kruskal-Wallis test

21. Results: Does type matching precede soft songs or wing waves (ie: is it hierarchical?) • For wing waves, NOT QUITE (but close: p=0.09) • For soft song, YES! (p= 0.005) Binomial theory Allaboutbirds.org

22. Discussion: Putting it all together The results support the hypothesis Song type matching is sign of escalation 90% of Early Type Match attacked First successful evidence that song typing is important in escalating Hierarchical signalling system

23. Unexpected anomalies

24. What could be improved? • Only one song was used • Time of year • Age of the Male kept consistent? • How long had the male been in that territory? • If the tape recorder played repertoire song instead of type matching would situation deescalate? As a control

25. Future research • Why some individuals not display their aggressive intentions? • Does signalling before an attack increase fitness or is it not advantageous? • Is signalling a genetic behaviour, learned behaviour or both? • Can this system be developed for other animals?

26. Friends and enemies: how social dynamics shape communications and song learning in song sparrows.(Michael D. Beecher, and CaglarAkcay) 2013 • Sparrow males learn about other males by eavesdropping and direct interactions • Dear-enemy relationship • Type Matching escalator and Repertoire matching is not aggressive • Type Matching used in early spring and Repertoire in late spring

27. Questions????

28. How do you think these threat signals (wing waves, soft songs) evolved? Do you think it is advantageous to only type match when threat is at the center of the territory and not at the boundary? • Ackayet al. claim they have shown that type matching elicits escalating aggressive behaviour (in a general sense). The methodology they used looks like it might have some limitations in making such a general claim…. What might they be? What are some other ways we could test this hypothesis (in completely new tests, or just to improve on the author’s methodology)? • In this study it was seen that some song sparrows do not sing or give any signal before attacking, what benefit, if any, would this deceptive signalling have?

29. References: Michael Beecher [Internet] [cited Oct. 23, 2013] Available from:http://faculty.washington.edu/beecher/ CaglarAkcay [Internet] [cited Oct. 23, 2013] Available from: https://faculty.cit.cornell.edu/caglar/AkcayWebCV.pdf Akçay, Ç., Tom, M., Campbell, S. E. & Beecher, M. D.  (2013)  Song type matching is an honest early threat signal in a hierarchical animal communication system.  Proceedings of the Royal Society of London, Series B., 280, in press. Templeton, C. N., Akçay, Ç., Campbell, S. E. & Beecher, M. D. (2012)Soft song is a reliable signal of aggressive intent in song sparrows.  Behavioral Ecology & Sociobiology, 66, 1503–1509. Templeton, C. N., Akçay, Ç., Campbell, S. E. & Beecher, M. D. (2012)  Soft song is a reliable signal of aggressive intent in song sparrows.  Behavioral Ecology & Sociobiology, 66, 1503–1509.