2. Acoustic Recognition of the Lamb by its Mother Frédéric Sèbe, Pascal Poindron, et Equipe Comportement, Neurobiologie et Adaptation Physiologie de la Reproduction et des Comportements UMR 6175 INRA – CNRS - Université de Tours - Haras Nationaux Nouzilly, FRANCE Adapted and translated for BiosciEdNet by Dwight Krehbiel, Dept. Of Psychology, Bethel College, North Newton, KS 67117, and Jerry Epp, biology instructor, USD 373, Newton, KS 67114 USA

3. Why study sounds in our laboratory? One of our main topics of research: maternal behavior in ewes One of our main topics of research: maternal behavior in ewes In particular, how are ewes able to recognize their lambs among dozens of others? In particular, how are ewes able to recognize their lambs among dozens of others? First, are they capable of such recognition? First, are they capable of such recognition? We will provide two brief experimental demonstrations to answer this question. We will provide two brief experimental demonstrations to answer this question. First experiment: will a ewe allow nursing by a lamb other than her own? First experiment: will a ewe allow nursing by a lamb other than her own? 2

4. Example of the lamb being recognized by the mother at the time of nursing (alien lamb presented first) 3

5. Conclusion: yes, she can! Conclusion: yes, she can! Second little experiment: Second little experiment: Test of preference between two lambs when the ewe cannot get closer than one meter (no role for odors). Test of preference between two lambs when the ewe cannot get closer than one meter (no role for odors). The test employs two lambs, one in each corner of a triangular pen, and the experimenter measures how much time is spent by the ewe in each corner. The test employs two lambs, one in each corner of a triangular pen, and the experimenter measures how much time is spent by the ewe in each corner. 4

6. Example of the ewe recognizing her lamb without the help of smell (familiar lamb is at right) 5

7. She can still do it! She can still do it! Can she do even better, that is, can she recognize her lamb just by hearing its bleats? Can she do even better, that is, can she recognize her lamb just by hearing its bleats? To answer this question we play the bleats of her lamb (or of another lamb – the alien lamb) through a loud speaker. To answer this question we play the bleats of her lamb (or of another lamb – the alien lamb) through a loud speaker. 6

8. Example of the mother recognizing the bleats of her lamb (playback through a loud speaker located to the right of the screen) 7

9. If one repeats this experiment on many ewes, also playing bleats of alien lambs... If one repeats this experiment on many ewes, also playing bleats of alien lambs... 8

10. Recognition of a lamb’s bleats by its mother % of ewes attracted by the bleats 9

11. But what is different between two voices? But what is different between two voices? Let’s take two human voices…. Let’s take two human voices…. Close your eyes and listen… Close your eyes and listen… 10

12. 11

13. Could you hear a difference? 12

14. And can you do the same thing with lambs? Now, still with your eyes closed, pay close attention, and let’s see what happens with several lambs. Which of the following is the same as the lamb you just heard? 13 Close your eyes and listen carefully to the first bleat…

15. 1234 14

16. So we see that we can hear the difference between two or more voices, human or animal, pretty well. So we see that we can hear the difference between two or more voices, human or animal, pretty well. But we might be embarrassed if someone asked us to explain how we can do this. But we might be embarrassed if someone asked us to explain how we can do this. To know more about this question we must run our sounds through specially designed computer programs. These programs provide displays like those on the next slide. To know more about this question we must run our sounds through specially designed computer programs. These programs provide displays like those on the next slide. 15

17. a) Spectrogram b) Oscillogram Duration Dmax time (sec) Frequency (kHz) FF Fmax c)Frequency spectrum % 3KHz Fundamental Frequency Harmonics MA Here are three graphical displays showing the physical characteristics of a bleat (and the same kind of display could be used for human voices). Frequency modulation – i.e. the up and down variations that you see on each trace 16

18. Let’s go back to the two human voices. Let’s go back to the two human voices. We can say that there is a male voice and a female voice. But what makes the difference between a male voice and a female voice, or between two voices in general? We can say that there is a male voice and a female voice. But what makes the difference between a male voice and a female voice, or between two voices in general? Let’s look at computer displays of the two human voices …. Let’s look at computer displays of the two human voices …. 17

19. Fundamental frequency = 190 to 290 Hz (high) FF = 130 to 180 Hz (low) Voice of a woman Voice of a man Note the FF and also the difference between the envelopes, the amplitudes, and the distribution of energy among harmonics – the timbre. We see a higher percentage of energy in the low frequencies for the male. 18

20. Fundamental Frequency = 260hz (high) FF= 160hz (low) Voice of a woman Voice of a man Here are equivalent sounds and displays for French speakers; they are saying "Bienvenue," which means "Welcome." 19

21. One can do the same thing with the bleats of lambs… One can do the same thing with the bleats of lambs… 20

22. Bleats of two different lambs Here for example, there is a clear difference in the distribution of the energy over time (amplitude modulation). 21

23. One can easily see the differences. One can easily see the differences. But does a ewe make use of these differences in recognizing her lamb? But does a ewe make use of these differences in recognizing her lamb? How can we answer this question? How can we answer this question? We modify the bleats. We modify the bleats. Please close your eyes !!! Please close your eyes !!! 22

24. Modified bleats 23

25. Original The lowest half of the frequencies (low-pitched) Modified bleats A constant value added to all the frequencies 200 Hz shift Percentage of ewes attracted by the bleats: 80%80% 90% 50% For comparison: (alien lamb: 15%) (shift 400Hz: 15%) (lowest 1/4: 17%) The highest half of the frequencies (high-pitched) 24

26. Modified bleats … Please close your eyes and listen... Please close your eyes and listen... 25

27. 26

28. Bleats played backwards Recognition by the mother: Yes No Yes Yes Overall: about 50% of mothers do not recognize the bleat of their own lamb when it is played backwards. Normal playback Backward playback Lamb A Lamb B Normal playback Backward playback 27

29. Summary of the Main Responses of Ewes to Modified Bleats Mean percentage of ewes responding to normal bleats of their own lamb % of ewes displaying recognition Overall increase in frequencies Modification by amplitude modulation Retaining only certain of the sound frequencies* Mean percentage of ewes responding to normal bleats of an alien lamb *corresponding to lower fourth, lower half, upper half of frequencies 28

30. In summary Ewes readily recognize the voice of their lamb (and lambs also recognize that of their mother, though we haven’t shown you that; you just have to believe us). Ewes readily recognize the voice of their lamb (and lambs also recognize that of their mother, though we haven’t shown you that; you just have to believe us). The fundamental frequency is the “skeleton” of a bleat and thus is part of the “individual signature” of a voice. The fundamental frequency is the “skeleton” of a bleat and thus is part of the “individual signature” of a voice. But recognition does not depend solely on any one feature of this sound. But recognition does not depend solely on any one feature of this sound. Other features of the sound, such as amplitude modulation and timbre (distribution of energy among different sound frequencies), also play an important role in recognition. Other features of the sound, such as amplitude modulation and timbre (distribution of energy among different sound frequencies), also play an important role in recognition. 29

31. We hope you enjoyed this little tour of our laboratory.