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Acoustic and Bioseismic Communication of Elephants by 						Alexandra Reed

Recording Methods: To study acoustic communication in elephants, a variety of specialized equipment is used. Elephants produce low-frequency vocalizations outside the range audible to the human ear. The three aspects of primary focus for the study of elephant communication are acoustic vocalizations, bio-seismic waves, and temporally and spatially associated behaviors (5). First, elephants, whether wild or captive, are fitted with specialized collars. These collars are equipped with low-frequency microphones and transmitters. Once acoustic vocalizations are recorded, the information is stored and analyzed. SpectraPlus sound analysis software is one program commonly used for analysis (2). Digital video cameras are also used to record behaviors at the time of each vocalization. This enables the formation of a hypothesis regarding potential links between behavioral and vocal patterns. In many captive studies, blood samples and endocrine measurements are gathered to track the reproductive status of individual females (3). This is important when examining the possible effects that reproductive status may or may not have on the calling behaviors of both female and male elephants. A hidden Markov Model, or HMM is used to identify the caller as well as to decipher specific vocalization types (6). This is important when considering what information a specific vocalization type transfers. In addition to many of the technologies listed above, geophones buried 10 cm under the ground are used when studying bio-seismic waves (4). Elephants have demonstrated significant capabilities for both low-frequency acoustic vocalizations as well as bio-seismic communication.

Acoustic Vocalizations: Elephants use infrasonic contact calls and a variety of vocalizations to communicate with each other. To date, 10 distinct vocalization classes have been identified through acoustic observation and recordings (2). These classes include the croak, rev, trumpet, snort, rumble, growl, bark, roar, and cry. By using only high quality recordings without background noise or disturbances, the accuracy rate for vocalization classification was calculated at 94.3% (6). The aim is to discover whether these various vocalizations transmit information regarding the callers' identity, breeding status, and emotional state. It has been postulated that the three main factors which influence calling behaviors are the dominance rank and reproductive status of the caller as well as the individuals' relationship to the caller (6). Female elephants are far more likely to responds to calls produced by related females. Elephants have significant potential for individual recognition through various calls. It is entirely possible that elephants have various accents and dialects due to variations between individual vocal tract structures (6). Furthermore, it has been documented that female elephants vocalize more frequently when one of more of them is ovulating. This may serve to help a female find a suitable mate. Additionally, calls exhibited during situations of aggression or competition may serve to either request support from allies, exhibit submissive signals, or to exhibit signals of distress (6).

Bioseismic Communication In addition to acoustic communication, elephants utilize bio-seismic waves as another form of communication. These bio-seismic waves, created by the animals’ movement, allow elephants to communicate over long distances because they can travel through the air and the ground (1). Elephants have what are called Pacinian corpuscles in the dermis of their feet which allow them to sense, and react to, bio-seismic waves. The specific distribution of Pacinian corpuscles in the elephants’ feet suggest they serve as a tool for the transmission of vibrations and seismic waves to the elephants’ somatosensory nervous system (1). A variety of physical and vocal behaviors have been observed from elephants in response to the propagation of seismic waves. It is entirely possible that the utilization of seismic waves is done in conjunction with acoustic vocalizations which would aid in effective long-distance communication between individuals or groups.

References

1.	[Bouley, D., Alarcon, C., Hildebrandt, T., O’Connell-Rodwell, C., 2007. The distribution, density, and three-dimensional histomorphology of Pacinian corpuscles in the foot of the Asian elephant (Elephas maximus) and their potential role in seismic communication, Anatomical Society of Great Britain and Ireland, 211: 428-435] 2.	[Clemins, P., Johnson, M., Leong, K., Savage, A., 2005. Automatic classification and speaker identification of African elephant (Loxodonta Africana) vocalizations, Journal of the Acoustical Society of America, 117: 956-963] 3.	[McComb, K., Moss, S., Baker, L., 2000. Unusually extensive networks of vocal recognition in African elephants, Animal Behavior, 59: 1103-1109] 4.	 [O’Connell-Rodwell, C., Hart, L., Arnason, B., 2001. Exploring the potential use of seismic waves as a communication channel by elephants and other large mammals, American Zoology, 41: 1157-1170] 5.	[Soltis, J., Leong, K., Savage, A., 2005. African elephant vocal communication 1: antiphonal calling behavior among affiliated females, Animal Behavior, 70: 579-587] 6.	 [Soltis, J., Leong, K., Savage, A., 2005. African elephant vocal communication 2: rumble variation reflects the individual identity and emotional state of callers, Animal Behavior, 70: 589-599]