Alouatta Palliata)
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LONG CALL FREQUENCY VARIATION IN MANTLED HOWLER MONKEYS (Alouatta palliata) by James Wheeler A Thesis Submitted to the Faculty of The Dorothy F. Schmidt College of Arts and Letters in Partial Fulfillment of the Requirements for the Degree of Master of Arts Florida Atlantic University Boca Raton, Florida December 2013 LONG CALL FREQUENCY VARIATION IN MANTLED HOWLER MONNKEYS By James Wheeler This thesis was prepared under the direction of the candidate's thesis advisor, Dr. Doug Broadfield, Department of Anthropology, and has been approved by the members of his supervisory committee. It was submitted to the faculty of the Dorothy F. Schmidt College of Arts and Letters and was accepted in partial fulfillment of the requirements for the degree of Master of Arts. SUPERVISORY COMMITTEE: Andrew Halloran, Ph.D. ~l>D(!~A. Kate Detwiler, Ph.D. Heather Cottman, DMA Interim Dean, Dorothy F. Schmidt College of Arts and Letters ~-r.~.-. 11 ACKNOWLEDGMENTS I would like to acknowledge the efforts of others in the culmination of this thesis for it was not the effort of one person, but many. I would like to thank Dr. Andrew Halloran for his help in Nicaragua, both with field research methods and teaching me PRAAT. I would like to thank Dr. Douglas Broadfield for his assistance both throughout school and throughout the lengthy pursuit of this document. Renee Molina and family were incredibly welcoming and hospitable, and I would like to encourage others to get in touch with them for all that they offer, from tourism to conservation; specifically, the Maderas Rainforest Conservancy is an incredible resource and benefit to the world. I would like to thank Leonel Ruiz for his assistance throughout my stay and his help in the forest; without him I truly would have been lost and lonely. I would like to thank the towns of San Ramon and Merida. I would like to thank the students of each of the primate field classes. I would also like to thank my family and friends for encouraging me to pursue this path and to stick with it. iii ABSTRACT Author: James D. Wheeler Title: Long Call Frequency Variation in Mantled Howler Monkeys (Alouatta palliata) Institution: Florida Atlantic University Thesis Advisor: Dr. Douglas Broadfield Degree: Master of Arts Year: 2013 The long call frequency of male mantled howler monkeys (Alouatta palliata) varies across individuals. In a forest environment where visual contact is impossible at greater distances the long call is utilized for inter-group spacing and for male-male communication. As lower frequencies are capable of traveling longer distances, it is quite possible that there is a correlation between group size and long call frequency. This link lies in the premise that smaller groups have fewer individuals thus fewer males, and spread out less over the course of each day while obtaining food resources, thus the distance these males call over their lifespan is generally less than the males in a larger group. This thesis investigates the relationship between group size and long call frequency in mantled howler monkeys (Alouatta palliata) on Isla de Ometepé, Nicaragua. iv LONG CALL FREQUENCY VARIATION IN MANTLED HOWLER MONKEYS (Alouatta palliata) List of Tables………………………………………………………………………….….vi List of Figures………………………….……….………………………………….……viii Introduction………………………………………...…….………………………………..1 Feeding Ecology……………………….………….………………………………2 Vocalizations………………………………………………………………………4 Group Size………….……………………………………………………………11 Thesis Statement……………………………………..……………………....…..13 Materials & Methods………….…………..………………………..…………....………14 Study Area…………………..……...….….……………………….……………14 Group Size……………………………….………………………………………19 Long Call Frequency……………………...……...………….…………………..21 Long Call Frequency Analysis………………………………..…………………22 Statistical Analyses………………………....…..……….……………………….31 Results……………………………………………………………………………………57 Discussion……………………………………………………………………………..…62 References……………………………….……………………………………………….66 v TABLES Table 1. Most Abundantly Utilized Trees Observed in Coffee Forest……………..…19 Table 2. Coffee Forest Howler Monkey Troop Demography…………………...…….20 Table 3. Coffee Forest Troop Size as Compared to Other Studies and Species……....20 Table 4. Coffee Forest Group Demographics as Compared to Clarke and Zucker (1994) Table 2 and Fedigan et al. (1998) Tables II & III……………............21 Table 5. General Distribution of Large Group’s (LG) Bark Frequencies…….……….32 Table 6. General Distribution of Large Group’s (LG) Roar Frequencies……………..32 Table 7. Statistical Analyses of Large Group Calls………………………………...…33 Table 8. Statistical Analyses of Very Large Group Calls……………………………..34 Table 9. Mean and Standard Variation Frequencies for VLG’s P1 & P2 Emphasized Frequencies…………………………………………………………………..52 Table 10. Mean and Standard Variation Frequencies for LG’s P1 & P2 Emphasized Frequencies……………………………………………………..52 Table 11. First Major Emphasized Frequency in each group’s P3……………………..53 Table 12. Second Major Emphasized Frequency in each group’s P3……………..........53 Table 13. Relationship of Peak 1 and Peak 2 frequencies in both groups….…………..54 Table 14. Peak 1 by vocalization type………………………………………………….54 Table 15. Peak 2 vocalizations by type…………………………………………………55 vi Table 16. Both Coffee Forest groups’s roars compared to Whitehead’s (1995) emphasized frequencies…………………………………………………...…56 vii FIGURES Figure 1. Drawing of apparatus used by Riede et al. to test simulated howler vocalizations ......................................................................................................9 Figure 2. Satellite Image of Ometepé with approximate location of the Coffee Forest................................................................................................................16 Figure 3. Coffee Forest Map (modified version of the original - by Falk Huettmann, 2009) ............................................................................................................... 17 Figure 4. Crude map of the Coffee Forest based on GPS coordinates acquired during walk-through ....................................................................................................18 Figure 5. Audiospectrogram of 3 barks ...........................................................................25 Figure 6. Spectral slice from 0 Hz to 104 Hz (abscissa) and relative decibel level (dB) (ordinate)… ............................................................................................ 26 Figure 7. Relationship of bands in spectrogram (left) and peaks in spectral slice (right, rotated counterclockwise 90°)…………………….……….……... ......27 Figure 8. Spectrum from Figure 5 - isolating frequencies from 0 to 5,000 Hz……. .....27 Figure 9. Spectral slice from previous spectrogram figures that isolates frequencies from 0 to 1,000 Hz………………………………………………. ..................28 Figure 10. Close-up of Peak 2 (P2) from previous figures; abscissa ranges from 376.0 Hz to 391.7 Hz…………………………….………… ..........................28 viii Figure 11. Peak 2 (P2) fully magnified with the highest part of the peak selected (380.881593 to 386.254339 Hz) providing 383.567966 Hz as the center of the tip of the peak………………………………………… .......................29 Figure 12. Frequency pairings between corresponding P1 and P2 values from Large Group calls (ordered from lowest P1 value to highest)……… .......................30 Figure 13. Simple graph demonstrating how Peak 1 freq.’s differ between groups .........35 Figure 14. Histogram of Large Group’s Peak 1 Vocalization Freq.’s (Hz – abscissa) .....36 Figure 15. Histogram of Very Large Group’s Peak 1 Vocalization Frequencies (Hz – abscissa)…………………………………………………………… .............. 37 Figure 16. Histogram comparing the distributions of long call frequencies for each group’s first peak frequencies………………………………… ......................38 Figure 17. Histogram comparing the distributions of long call frequencies for each group’s second peak frequencies…………………………………… .............39 Figure 18. Histogram comparing the distributions of long call frequencies for each group’s third peak frequencies………………………………… .....................40 Figure 19. P1 and P2 distribution of Large Group long call frequencies (300 – 650 Hz)…………………………………………………… .................41 Figure 20. P1 and P2 distribution of Large Group long call frequencies (650 – 3,000 Hz)…………………………………………… ......................... 42 Figure 21. Distribution of Large Group’s third peak frequencies (by type) (0 – 3,000 Hz)…………………………………………………… ..................43 ix Figure 22. Distribution of Large Group’s third peak frequencies (by type) (3,000 – 6,500 Hz)………………………………………………………...…44 Figure 23. Distribution of VLG’s P1 emphasized frequencies (by type)………………..45 Figure 24. Distribution of VLG’s P2 emphasized frequencies (by type)…………….….46 Figure 25. Distribution of LG’s P1 emphasized frequencies (by type)……………….…47 Figure 26. Distribution of LG’s P2 emphasized frequencies (by type)……………….…48 Figure 27. At all markers VLG P1 has higher frequencies……………………………...49 Figure 28. VLG and LG are fairly similar throughout the distribution of frequencies for P2…………………………………………………...……….50 Figure 29. General distribution of P3 frequencies for both groups…………….………..51 Figure 30. Map showing location of Beach Forest……………………………….……..64 x INTRODUCTION The mantled howling monkey (Alouatta palliata) is a relatively large arboreal and diurnal New World primate belonging to the family Atelinae (Rowe, 1996; Fleagle, 1999). “A. palliata is placed as the sister taxon to all other Alouatta species” (Villalobos, 2004). Cortés-Ortiz