This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Tokay geckos (Gekko gecko), large and mostly nocturnal geckos native to parts of Asia, are among the few nonbird reptiles that make sounds to attract potential mates, defend their territory and signal distress. Male tokay geckos' calls typically begin with quieter rattles, followed by louder two-part sounds that can sound like "ge-ko" or "to-kay." Past studies suggest that in noisy environments, male tokay geckos can produce more of the louder "GE-KO" sounds and make them last longer.
How they manage to extend these sounds while breathing had remained unclear. Researchers at the University of Southern Denmark recently set out to better understand the physiological processes that allow male geckos to extend their two-part calls. Their findings, outlined in a paper published in Proceedings of the Royal Society B: Biological Sciences, revealed that geckos take a brief breath between the two parts of a call and add pulses to the second part to make it last longer.
"Although previously considered inflexible, male tokay geckos exhibit vocal plasticity by switching to longer, louder call types in noisy environmental conditions," wrote Mathilde S. Fuglsang Thastum, Danuta M. Wisniewska, Jakob Christensen-Dalsgaard and Coen P.H.
"However, they seem to face respiratory constraints limiting longer duration calls. To test this hypothesis, we combined acoustic analysis with deep learning-based pose estimation to quantify respiratory dynamics during spontaneous advertisement calling." Male tokay geckos typically use calls to attract potential female mates or communicate with other males. The researchers collected and analyzed 16 video clips of seven captive male tokay geckos spontaneously making sounds.
"Calls were produced exclusively during expiration at a constant rate, supporting the hypothesis that respiratory constraints limit call duration," wrote Thastum, Wisniewska and their colleagues. "Tokays use two mechanisms to increase bi-note call duration. First, bi-notes contain an inspiratory 'mini-breath'—a feature previously associated only with songbirds.
Second, bi-note duration is increased by adding terminal pulses, whose acoustic signatures suggest vocal fold oscillation in the air-efficient vocal fry register." The researchers also tracked movement in the geckos' backs, bellies and ear openings. This helped them identify when the animals breathed in and out and when their ear openings narrowed. Finally, they searched the recordings for acoustic signs of "vocal fry," a low, creaky mode of voice production also observed during human speech.
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