Author: Matija GOGALA, Ljubljana
The article carrying this title was published in Muzikološki zbornik (Musicological Bulletin), 33 (1997): 5-21, published in Ljubljana, Slovenia.
Several examples of animal sounds or vibration signals referred to in this article are presented in the form of oscillograms and sonograms. For a better notion of this communication, the following examples of animal sounds and vibration signals are presented.
Numerous insects produce vibration signals and tunes, most interesting among them being those produced by true bugs (Heteroptera) of the Cydnidae family. They do so by two different mechanisms, stridulation, rubbing together serrated body parts, body shaking, or with the simple timbal. For their communication, only the vibrations on the ground are important, not the sound transmitted through the air.
Our example is the Pied Shieldbug (Tritomegas bicolor).
As soon as touched, attacked or otherwise disturbed, this species produces, by stridulation, short irregularly repeating stridulation signals, called excitation signals.
Of greater interest are the vibrational songs that can be heard during the insects’ courtship and mating. Males produce the first courtship song (MS-2) with repeated phrases consisting of a low-frequency part, followed by three or four stridulatory sounds. If the female is ready to mate, she will respond with a long sequence of short stridulation signals (FS-2). After a while, the male shifts to an intense second courtship song (MS-3). These signals can be heard as an entire sequence and can be seen individually in the following illustrations:
The second related bug is Sehirus luctuosus. The male’s (vibrational) courtship song is highly reminiscent of a jazz musician’s drum solo.
The following interesting example is the acoustic behaviour of the predatory species Phymata crassipes.
This species produces several vibration songs. One of them is used alternately by males, females and even juveniles. Let us listen to two alternating individuals. These bugs also respond with this kind of vibrational signals to various sounds and even to human speech or whistling and copy the duration of such sounds. You can listen to this kind of alternation between the bug (Ph) and the performer of the test (H), and see the sonagram below:
Even more surprises wait for us in the acoustic world of tropical and subtropical countries – where the endangered natural ecosystems still exist. The author had the opportunity to study the fascinating songs of Southeast Asian cicadas and the sounds of other animals in the rainforests of Malaysia and Thailand.
Contrary to European cicadas, some species sing there like birds with a high degree of frequency modulation, which sounds like this:
The number of singing cicadas is so high in certain places that they have to share their singing time with other species in a precise order to make the communication effective. For this reason, the sounds in rainforests change from hour to hour, as shown in the following examples from Belum Forest in Malaysia.
More examples of songs produced by tropical cicadas can be heard on the page with Asian cicadas.
Several tropical bird songs are surprising, too. Some are sung major or minor scales up (a) or down (b) like Myiophoneus caeruleus (a – see below!)
An example of the extremely complex and fantastically coordinated animal singing, which I heard and recorded in Taleban National Park (Thailand), was the singing by two gibbons in polyphony. Let us listen to a short excerpt of this consonant glissando, which is also presented on the graph below.
Summary
The bulk of the examples presented in the first part of this article deals with vibrational songs of European bud species (Insecta: Heteroptera), whereas in the second part, the songs of animals (cicadas, birds and mammals) were recorded in the tropics. The biodiversity of tropical rainforests is mirrored in the wealth of sound backgrounds, particularly in Southeast Asia. The author was all the more impressed during his expeditions by the sonic diversity of tropical cicadas, with an unusually high degree of frequency modulation for insects and many species singing exclusively during specific hours of the day or night. These countries are also inhabited by a series of birds that sing up and down the scales and gibbons that sing in polyphony. The entire sound background of an undisturbed tropical rainforest is an endless symphony of nature, changing from hour to hour, and culminating at dusk.
A number of cassettes and CDs have been produced with recordings of sound backgrounds or with selected animal sounds – as a replacement of adventures in nature, for meditation, as an interesting soundtrack or for scientific purposes. Some composers utilize recordings of animal sounds as a source of new ideas or even as material for bioacoustic compositions*). The digitized audio examples used in this article are available on this website. Perhaps, however, it would be best just to listen carefully to all these voices in nature.
*) As an example, let us listen to the “bioacoustic composition” titled Touches by the composer Boštjan Perovšek. This piece includes the sounds of synthesizer, accordion, and the voices of over 16 species of crickets, cicadas, bugs, bees, birds, frogs and toads.