Acoustic Communication in Captive Asian Elephants
(Elephas maximus)

Sharon S. Glaeser 1,2,*

1 Department of Biology, Portland State University, P.O. Box 751, Portland, OR, 97207, USA
2 Oregon Zoo, 4001 SW Canyon Road, Portland OR, 97221, USA
* contact email: sharon@roguetechinc.com

Short Intro

Portland State graduate student Sharon Glaeser is studying acoustic communication in the zoo’s Asian elephants. Relatively little is known about the vocal repertoire of Asian elephants. This project aims to define an acoustic repertoire, to investigate variability and individuality, to develop a call recognition algorithm through collaboration, and to provide a basis for comparisons between captive and wild elephants and between Asian and African elephants.

Abstract

Asian elephants (Elephas maximus) are listed as endangered, and African elephants (Loxodonta spp.) are listed as endangered or threatened, so there is a conservation value for understanding the communication and ecology of both genera. Relatively little is known about the vocal repertoire of Asian elephants. Our knowledge of acoustic communication in elephants is based primarily on research on three wild African elephant  populations (Amboseli National Park, Tanzania; Etosha National Park, Namibia; central African forests), two captive African elephant herd (Disney's Animal Kingdom, Orlando, FL, USA and Vienna Zoo, Vienna, Austria), one wild Asian elephant population (Gal Oya National Park, Sri Lanka), and one captive Asian elephant herd (Oregon Zoo (formerly Washington Park Zoo), Portland, OR, USA). Over 30 calls have been published for African savannah elephants (Loxodonta africana), but only nine calls have been published for Asian elephants [1, 2]. There are many unknowns with regards to acoustic communication in Asian elephants. Vocal individuality has been found in other mammalian species [3, 4], and structural variation within a call may serve a communicative function [5], but calls must first be defined. A categorization of basic call types and modifications of these call types by quantitative acoustic parameters is needed to examine acoustic variability within and among call types, to examine individuality, to determine meaning of calls via playback, and to develop rigorous call recognition algorithms for acoustic monitoring and census of wild populations. African elephants are capable of producing calls ranging from 5Hz to 9kHz [6]. Infrasonic calls (below 20 Hz) have been recorded from captive Asian elephants [7], but the frequency range of Asian elephant vocalizations is unknown. In addition it is unclear whether Asian males produce a vocalization unique to musth similar to the musth rumble produced by African elephants [8].  By studying communication of known inviduals in the more controlled setting offered by captivity, more rigorous analyses can be done with regards to individuality, social context, variability, reproductive state, and perceived emotional state. 

This project aims to categorize sounds by acoustic parameters, to define an acoustic repertoire of captive Asian elephants, to examine functional relevance of acoustic variability in a captive environment, to investigate individuality, to examine the function of low-frequency communication in captivity to determine potential impact of low-frequency anthropogenic noise, and to provide a dataset for developing call recognition and individual recognition algorithms for the Asian elephant acoustic repertoire. Finally, this study aims to provide a basis for comparisons of acoustic communication in wild and captive Asian elephants, and could potentially serve as a basis for comparisons between Asian and African elephants. These comparisons may provide insights into the ecological role such communication plays and the requirements of counterpart populations. As elephants lose habitat and find themselves under varying degrees of management, the need to understand their requirements in captivity will become even more important to the survival of the species [9]. The acoustic repertoire collected and defined by this project will be  contributed to a library of calls of known Asian elephants in known reproductive states; and the definitions of behaviors and vocalizations will be contributed to the ethogram published in the Elephant Husbandry Resource Guide, which provides a comprehensive list of behavior observed over many years by many researchers and elephant handlers [1].

REFERENCES

1.    Olson, D., ed. Elephant Husbandry Resource Guide. 2004, International Elephant Foundation. 280.
2.    McKay, G.M., Behavior and ecology of the Asiatic elephant in southeastern Ceylon, in Smithsonian        Contributions to Zoology. 1973, Smithsonian Institution Press: Washington, DC. p. 1-113.
3.    Darden, S.K., T. Dabelsteen, and S.B. Pedersen, A potential tool for swift fox (Vulpes velox)        conservation: Individuality of long-range barking sequences. Journal of Mammalogy, 2003. 84(4):        p. 1417-1427.
4.    Reby, D., et al., Individuality in the groans of fallow deer (Dama dama) bucks. Journal of Zoology        (London), 1998. 245: p. 79-84.
5.    Soltis, J., K. Leong, and A. Savage, African elephant vocal communication II: rumble variation        reflects the individual identity and emotional state of callers. Animal Behaviour, 2005. 70(3): p.        589-599.
6.    Poole, J.H., Elephant vocal communication. In: The Amboseli Elephants: A long-term perspective on        a long-lived mammal, ed. C.M.H. Croze. in prep, Chicago: University of Chicago Press.
7.    Payne, K.B., W.R.L. Jr., and E.M. Thomas, Infrasonic calls of the Asian elephant (Elephas maximus).        Behavioral Ecology and Sociobiology, 1986. 18: p. 297-301.
8.    Poole, J.H., Rutting behavior in African elephants: the phenomenon of musth. Behaviour, 1987.        102: p. 283-316.
9.    Riddle, H.S., B. Rasmussen, and D.L. Schmitt, Are captive elephants important to conservation?        Gajah, 2003. 22: p. 57-60.

Characterization of female Asian elephant
(Elephas maximus) estrous cycles through longitudinal serum progestagen monitoring at Oregon Zoo

Meghan S. Martin1, Sharon S. Glaeser1, Mitch Finnegan, DVM1, and Janine L. Brown2

1 Oregon Zoo, Portland, Oregon, USA
2 Conservation and Research Center, National Zoological Park, Smithsonian Institution, Front Royal    Virginia, USA

Short Intro

Oregon Zoo Research Associates Meghan Martin and Sharon Glaeser are collaborating with Oregon Zoo Veterinarian Dr. Mitch Finnegan and Research Physiologist Dr. Janine Brown of the Smithsonian National Zoological Park on a study characterizing female Asian elephant estrous cycles through longitudinal serum progesterone monitoring of the Oregon Zoo elephants over the past 18 years.  This dataset represents the most comprehensive analysis of within and between animal variability in progestagen profiles, and the knowledge gained on estrous cycle dynamics should prove valuable in both ex situ and in situ management.

Abstract

Long-term hormone analyses is needed for investigations of estrous cycle characteristics, impact of biologically significant events on cycle variation, synchronicity among females in a group, and ovarian inactivity or acyclicity within individuals. Regular monitoring of hormone activity is required to characterize estrous cycle dynamics, and ex situ managers monitor hormone activity as well as contribute to disease detection studies through weekly blood collections of trained elephants. Using samples from captive elephants, researchers at the Smithsonian National Zoological Park have developed a fecal field kit for monitoring hormone activity in free-ranging elephants, which provides a new tool for making conservation management decisions in range countries.

Estrous cycle monitoring is used in ex situ management to predict ovulation in order to facilitate male/female socialization of captive elephants while avoiding unwanted pregnancies and to schedule natural breeding. This effort requires a complete characterization of estrous cycle parameters for each female in the herd and is accomplished by measuring serum progestagen concentrations. Concurrent monitoring of male behavioral indices of female fertility (e.g., flehmen response) can aid in predicting ovulation, but this is not always practical. This study summarizes longitudinal progestagen data of female elephants at the Oregon Zoo over the past 18 years.  Chart review of weekly progestagen results were used to assess the estrous cycles of nine Indian elephants (E. maximus indicus) and one Borneo elephant (E. maximus borneensis), for a total of over 120 cycles encompassing puberty through senescence. Estrous cycle duration, lengths of luteal and non-luteal phases, peak progestagen concentrations, and luteal phase midpoints within each cycle are reported for each individual. Of interest to this current study is the assumption that cycle length is variable among cows, but is more consistent within an individual .  However, prior to this study, no long-term analyses (i.e., >5 years) of progestagen profiles had been conducted to examine the degree of cycle variation within and across individuals, especially in relation to age and season. This dataset represents the most comprehensive analysis of within and between animal variability in progestagen profiles, including evaluations of: 1) age at first cycle (first pubertal luteal phase); 2) cyclic changes associated with age; 3) presence or absence of estrous synchrony; and 4) variations in cyclicity relative to biologically significant events. Results indicate significant variability in progestagen profiles within and between animals as well as some degree of synchrony. Further analyses are being done.

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