Asian Elephant Vocalizations

Introduction

Asian Elephant Vocalizations, Linguistic Data Consortium (LDC) catalog number LDC2010S05 and isbn 1-58563-557-X, consists of 57.5 hours of audio recordings of vocalizations by Asian Elephants (Elephas maximus) in the Uda Walawe National Park, Sri Lanka, of which 31.25 hours have been annotated. Voice recording field notes were made by Shermin de Silva and Ashoka Ranjeewa, of the Uda Walawe Elephant Research Project. The collection and annotation of the recordings was conducted and overseen by Shermin de Silva, through the University of Pennsylvania Department of Biology, and Institute for Research in Cognitive Science. The recordings primarily feature adult female, and juvenile elephants. Existing knowledge of acoustic communication in elephants is based mostly on African species (Loxodonta africana and Loxodonta cyclotis). There has been comparatively less study of communication in Asian elephants, primarily becaUse the habitat in which Asian elephants typically live makes them more difficult to study than African forest elephants. For other current elephant vocalization research, see ElephantVoices and the Cornell Lab of Ornithologys Elephant Listening Project.

This corpus is intended to enable researchers in acoustic communication to evaluate acoustic features and repertoire diversity of the recorded population. Of particular interest is whether there may be regional dialects that differ among Asian elephant populations in the wild and in captivity. A second interest is in whether structural commonalities exist between this and other species that shed light on underlying social and ecological factors shaping communication systems.

Methods

Study site and subjects

Uda Walawe National Park (UWNP), Sri Lanka, is located at latitude 630°14.0646N, longitude 80°5428.1268E, and an average altitude of 118 m above sea level. It occupies 308 km² and contains tall grassland, dense scrub, riparian forest, secondary forest, rivers and seasonal streams. It also contains several natural and man-made water sources and reservoirs with seasonal floodplains. There are two monsoons per calendar year, separated by dry seasons of variable length. Over 300 adult females have been individually identified in UWNP using characteristics of the ears, tail, and other natural markings (Moss, 1996).

Data collection

Data were collected from May, 2006 to December, 2007. Observations were performed by vehicle during park hours from 0600 to 1830 h. Most recordings of vocalizations were made using an Earthworks QTC50 microphone shock-mounted inside a Rycote Zeppelin windshield, via a Fostex FR-2 field recorder (24-bit sample size, sampling rate 48 kHz) connected to a 12 V lead acid battery. Recordings were initiated at the start of a call with a 10-s pre-record buffer so that the entire call was captured and loss of rare vocalizations minimized. This was made possible with the pre-record feature of the Fostex, which records continuously, but only saves the file with a 10-second lead once the record button is depressed. In order to minimize loss of low-frequency or potentially inaudible calls, recording was continued for at least three minutes following the end of vocalization events. During the first two months, hour-long recording sessions were also carried out opportunistically while in close proximity to a group. However, spectrograms showed that few vocalizations were captured therefore, this was discontinued.

Anomalies

Some audio files have 1 channel (field recording) and some have 2 channels (field recordings and field notes).

Certain files were recorded at 22050 Hz sample rate:

• asian_elephant_voc_d1/data/20070209/B13h00m34s09feb2007y.flac
• asian_elephant_voc_d1/data/20070209/B13h10m04s09feb2007y.flac
• asian_elephant_voc_d2/data/20070405/B14h56m48s05apr2007y.flac
• asian_elephant_voc_d2/data/20070409/B14h35m11s09apr2007y.flac
• asian_elephant_voc_d2/data/20070409/B14h38m34s09apr2007y.flac
• asian_elephant_voc_d2/data/20070409/B14h39m27s09apr2007y.flac

Certain files were recorded at 16 bits per sample:

• asian_elephant_voc_d1/data/20070209/B13h00m34s09feb2007y.flac
• asian_elephant_voc_d1/data/20070209/B13h10m04s09feb2007y.flac
• asian_elephant_voc_d2/data/20070405/B14h56m48s05apr2007y.flac
• asian_elephant_voc_d2/data/20070409/B14h35m11s09apr2007y.flac
• asian_elephant_voc_d2/data/20070409/B14h38m34s09apr2007y.flac
• asian_elephant_voc_d2/data/20070409/B14h39m27s09apr2007y.flac
• asian_elephant_voc_d3/data/20070507/B08h37m21s07may2007y.flac
• asian_elephant_voc_d4/data/20070822/B08h44m02s22aug2007y.flac
• asian_elephant_voc_d4/data/20070822/B08h48m02s22aug2007y.flac
• asian_elephant_voc_d4/data/20071015/B12h25m22s15oct2007y.flac
• asian_elephant_voc_d4/data/20071015/B12h59m51s15oct2007y.flac
• asian_elephant_voc_d5/data/20071024/B16h12m29s24oct2007y.flac

One file contains audio extracted from a video recording at 16-bit, 32 kHz. This file may overlap with other audio recordings, but was used to aid annotation because of the density of vocalizations and the number of vocalizing individuals:

• asian_elephant_voc_d1/data_from_video/20070724/20070724_g01_vocs.flac

Audio data annotation

Certain audio files were manually annotated, to the extent possible, with call type (see below for a list of categories), caller id, and miscellaneous notes. Annotations were made using the Praat TextGrid Editor, which allows spectral analysis and annotation of audio files with overlapping events. Annotations were based on written and audio-recorded field notes, and in some cases video recordings. Miscellaneous notes are free-form, and include such information as distance from source, caller identity certainty, and accompanying behavior. Audio files that are included without a corresponding Praat TextGrid annotation file have not yet been annotated.

Acoustic features

There are three main categories of vocalizations: those that show clear fundamental frequencies (periodic), those that do not (a-periodic), and those that show periodic and a-periodic regions as at least two distinct segments. Calls were identified as belonging to one of 14 categories:

Audio compression (FLAC)

All audio wav files in this corpus have been compressed using FLAC (Free Lossless Audio Codec). Becuase FLAC is a lossless compression algorithm, the conversion of the included FLAC files into wav files will result in files that are sample-for-sample identical to the original wav file recordings.

Many standard audio tools (including Praat TextGrid Editor) will transparently decompress FLAC files, so that they may be played, processed, and examined as if they were uncompressed audio. Should you wish to explicitly decompress FLAC files (by converting them into wav files), there are many free audio tools capable of performing this conversion. Some such tools, available for all major operating systems, may be found at http://flac.sourceforge.net/download.html

The data in this corpus were used by the corpus author as the foundation of a paper, Acoustic communication in the Asian elephant, Elephas maximus maximus (S. de Silva Behaviour, Volume 147, Number 7, 2010, pp. 825-852). If you have trouble accessing the paper through the preceding link, you may contact the corpus author directly for assistance.

Sample

A sample of data available in this corpus: Audio recording Praat TextGrid Annotation

Updates

No updates are available at this time.