Peran testosteron dalam proses belajar menyanyi pada burung

 

Ilustrasi pengaruh pemberian testosterone pada burung

Ini sekadar sharing mengenai berbagai hasil penelitian tentang peranan testosterone dalam proses belajar menyanyi pada burung, sebagaimana ditulis Peter Marler (Department of Neurobiology, Physiology and Behavior University of California, USA) dalam buku Nature’s Music The Science of Bird Song yang dia susun bersama Hans Slabbekoorn (Institute of Biology, Leiden University, Leiden, Netherlands).

Secara garis besar disebutkan bahwa kicau burung jantan umumnya dianggap sebagai karakteristik seksual sekunder yang khas, dan berada di bawah kendali hormon steroid dari gonad. Hal ini terkait dengan pertumbuhan dan regresi testis.

Nyanyian burung jantan biasanya bertambah dan berkurang sesuai dengan fluktuasi testosteron di dalam darah. Ada reseptor testosteron di dalam syrinx (salah satu organ yang berfungsi sebagai penopang utama bagi bangsa burung untuk berkicau).

Dalam penelitian diketahui:

1. Tingkat kegacoran akan menurun ketika burung dikebiri, dan pengobatan dengan testosteron terbukti mengembalikan kegacorannya.
2. Testosteron sangat diperlukan untuk membuat burung menyuarakan lagu secara maksimal.
3. Testosteron tidak/ kurang berperan dalam proses pemasteran burung.

Untuk memberikan gambaran secara lengkap kepada Anda, di bagian bawah nanti saya sajikan tulisan lengkap Peter Marler di buku Nature’s Music The Science of Bird Song yang khusus membahas peran testosterone dalam proses pembelajaran burung kicauan.

Cara meningkatkan testosteron

Tulisan ini saya sharing untuk memberikan pemahaman mengenai perlunya meningkatkan jumlah testosterone pada burung jantan jika kita menginginkan burung bisa menampilkan performa suara yang maksimal, baik di rumah maupun di arena lomba.

Peningkatan jumlah testosterone bisa dilakukan dengan:

1. Pemberian pakan dan atau asupan lain dengan kandungan nutrisi yang seimbang, vitamin dan mineral serta sejumlah asam amino lain. (Sekadar catatan, ini adalah salah satu dasar yang Om Kicau pakai dalam peracikan produk-produk untuk burung seperti BirdVit, BirdShout, BirdMature dan lain-lainnya).
2. Penyuntikan hormon testosterone secara langsung kepada burung. Hanya saja, pemberian testosterone yang kelewat dosis dengan cara penyuntikan bisa membuat burung “kepanasan” dan menyebabkan rontok bulu.

Peter Marler: The Role of Testosterone in Song Learning

Male birdsong is generally regarded as a typical secondary sexual characteristic, under the control of steroid hormones from the gonads. It is associated with testis growth and regression. Male song usually waxes and wanes seasonally with the fluctuation in testosterone levels in the blood. There are testosterone receptors in the syrinx. Song decreases after adult castration, and testosterone treatment reinstates it.

The administration of testosterone induces song in females, and augments it in intact males. In the field, the testosterone profiles of males in spring correlates well with seasonal song development, although when they peak there seems to be a reduction in vocal plasticity (Nottebohm 1993). Testosterone has long been viewed as a major factor in song acquisition as well as production, presumed to act either directly on the brain, or after aromatization into estrogen within the brain.

The dogma was so well entrenched that when the first report was published of young male zebra finches (9 males) learning to sing normally after castration, it was greeted with skepticism. Despite his careful precautions, suspicions lingered that Arnold (1975) might have left fragments of the testis behind. Then Kroodsma (1986) reported a similar result with marsh wrens (3 males) that was again met with a degree of skepticism.

Only when ethologists and endocrinologists joined forces, and confirmed that testosterone was absent from the blood of male castrates, were critics finally convinced (Marler et al. 1988). Their subjects were song and swamp sparrows, castrated at 3–4 weeks of age (17 males) and then tutored with a changing program of tape-recorded songs. Almost all birds learned from the tutor tapes. They came into song about a month later than normal, passing through subsong, then plastic song. They progressed far enough to tell that learning had taken place, and had occurred at the normal time. Rather than crystallizing song, however, they persisted with plastic song, and then regressed, much as reported earlier by Arnold and Kroodsma for castrated zebra finches and marsh wrens. Five castrated swamp sparrows were then treated with testosterone. Within 3 weeks they all produced normal crystallized song.

It seems that testosterone is not required for song memorization and the early stages of production, but is needed for song crystallization. Hormone assays confirmed that all but three of the castrations were complete. Unexpectedly, estradiol was found in the blood of both castrated and intact male sparrows, suggesting that it might have a role in song learning. The source of the estradiol is not known, but there are indications that it may originate within the brain itself (Schlinger & Arnold 1991).

Salam, Om Kicau.