Je, twiga anatoa sauti?

(Scroll down for Swahili)

Most of us have never really heard a giraffe make sound. Maybe we have heard them grunt when fighting or heard a giraffe snort in alarm, but have you ever heard a giraffe make a sound? Giraffe faces don’t have that many expressions, they tend to just look at you, kind of curious. We don’t see a lot of facial interactions and they don’t seem to be communicating with each other, but like elephants and their cousin the Okapi, giraffes produce low frequency sounds.

In an article published in 1993, a doctor was discussing the amazing adaptations of the voice box or larynx, and suggested that giraffe might suffer from degeneration of the nerve that goes to the voice box called the laryngeal nerve. This is a disease that affects thoroughbred horses and is basically caused by the nerve being too big to feed itself and stay alive. The nerve that goes from the brain to the voice box is the longest cell in a giraffe and that might be the same problem. But giraffes are not inbred like thorough bred horses and the nerve and voice box are well developed. Over time, nature tends to put less energy into developing useless anatomy so the fact that they are well developed in giraffe suggests the voice box and nerve are being used.

A couple of recent studies on giraffe sound have discovered that giraffes actually do produce sound. One study in zoos in Germany discovered that giraffes hum at night when they are separated. The hum is loud and high enough for us to hear it. Another study in the US discovered that giraffes make the same sounds that Okapi make- usually when a mother goes up to her calf. They produced two types of sound- one was high enough for us to hear, the other was lower than what we can hear, but both sounds were produced with a deliberate movement of stretching the head out. These sounds are produced in a different way than vibration of the vocal chords, but rather the same way you make a sound when you blow over the top of a bottle. We still have a lot of research to do on giraffe sound but one thing we do know is that they do produce sounds but we’re just not tuned in to hear them.

Swahili version

Karibia sisi sote hatujawahi kusikia twiga akitoa sauti. Labda umewasikia wakiguna wakipigana au akidhihaki kwa tahadhari, lakini  umewahi kusikia akitoa sauti? Uso wa twiga huwa haionyeshi ishara za kujieleza na huwa wanakuangalia tu. Huwa hatuoni mawasiliano ya sura wala hawaonekani kuwasiliana wenyewe kwa wenyewe, lakini kumbe twiga anatengeneza sauti yenye marudio ya chini kama vile tembo na mnyama mwenzio wa twiga wa msituni anayeitwa ‘okapi’.

Kwenye nakala ilitolewa mwaka 1993, kuna daktari alizungumzia kuhusu mabadiliko maalum ya zoloto ya twiga, na alipendekeza kuwa twiga anateseka na chembe ya fahamu ya kutoka kwenye ubongo kuenda kwenye zoloto kufifia. Hii ni ugonjwa linaloathiri farasi wa aina ya ‘thoroughbred’, na kwa ufupi ni upungufu wa uwezo wa chembe hiyo kujilisha na kuishi. Hiyo chembe ya fahamu ya kutoka kwenye ubongo kwenda kwenye zoloto ni chembe kubwa kuliko zote mwilini mwa twiga na kulikuwa na uwezekano ya kwamba wanaweza kuwa na tatizo hiyohiyo. Lakini twiga hawazalishwi kama farasi hao, na zoloto pamoja na chembe hicho zimekomaa vizuri. Kawaida kama kuna chochote mwilini kisichotumika, huwa nguvu hupungua lakini kwa kuwa zimekomaa vizuri inapendekeza kwamba inatumika.

Kuna utafiti umefanyika karibuni na ikagunduliwa kwamba kumbe twiga wanatoa sauti. Utafiti uliofanyika kwenye bustani ya wanyama Ujerumani, imegundua kwamba twiga huwa anavuma usiku wakitenganishwa twiga na wenzio. Sauti hiyo ina nguvu na hata sisi binadamu tunaweza kuisikia. Utafiti mwingine uliofanyika kwenye bustani ya wanyama Marekani uligundua kwamba twiga wanatoa sauti inayofanana na sauti ya Okapi, huwa kawaida mama akimsogelea mtoto wake. Wanatoa sauti aina mbili- mmoja ina kiasi cha mawimbi juu kutosha hadi tuwezi kuisikia, na sauti nyingine ya chini ambayo hatuwezi kuisikia. Sauti hii haitengenezwi na vitisiko vya mishipa ya sauti. Inatengenezwa na namna tunavyopuliza juu ya chupa na kupata sauti. Baado utafiti mwingi unahitajika ili kuelewa kuhusu sauti ya twiga, lakini tunafahamu ya kwamba wanatoa sauti, tatizo tu ipo kwenye uwezo wetu kuisikia.

SOURCES

Kirchner, J. 1993. The Vertebrate Larynx: Adaptations and Aberrations. Laryngoscope 103. 1993.

Baotic, A., Sicks, F. & Stoeger, A.S. Nocturnal “humming” vocalizations: adding a piece to the puzzle of giraffe vocal communication. BMC Res Notes 8, 425 (2015).

Mugenthaler, E. 2013 Giraffe Helmholtz resonance. Acoustical Society of America.

Wedel, M. 2012. A monument of inefficiency: The presumed course of the recurrent laryngeal nerve in sauropod dinosaurs. Acta Palaeontol.