Vocal flexibility in geckos

Tokay gecko (Gekko gecko) in Thailand. Photo by Tontan Travel. 

This week's paper is from Proceedings of the Royal Society B, authored by Henrik Brumm and Sue Anne Zollinger at the Max Planck Institute for Ornithology. Brumm and Zollinger are the first to show flexibility in vocalizations by a reptile, and how the geckos do it is pretty cool. When we humans are trying to communicate in a noisy space, we usually yell at each other (i.e. increase our amplitude - technically called the Lombard effect). Tokay geckos, Gekko gecko, are native to Southeast Asia. They have a distinctive call, and in fact both the names "gecko" and "tokay" are onomatopoeia for the way the call sounds. Geckos in noisy environments have a different strategy for being heard. 

What they did

The methods for this study are very simple. They had male geckos in captivity in rooms lined with acoustic absorbing material and a microphone. For 24 hours white noise was broadcast to the geckos in the room, and their calls were recorded, and then for 24 hours there was silence and their calls were recorded. They repeated this to record four total days of calls. They then compared call duration, structure, and amplitude during noise and during silence. 

What they found

Geckos did not increase the amplitude of their calls, but they did increase the duration of the call syllables. This should also make them easier to hear. Additionally, Geckos have two types of calls, a softer cackle and the loud "Gecko!" Geckos in noisy environments make more of the louder gecko and less of the quieter cackle. They therefore are selecting to use more of the call types that are easier to hear when they are in noisy environments. 

The takeaway

Vocal flexibility in the form of the Lombard effect has been demonstrated in birds, mammals and even frogs. This is the first demonstration of vocal flexibility in reptiles, but also importantly, it is a different type of flexibility. Increasing the duration of syllables and perhaps selecting different words are tools that we use to communicate in noisy environments, but have not been reported as much in other animals. I am really interested in the use of these two different strategies, both duration increase and use of different calls. The white noise that the author's used is really broadband noise. I wonder if geckos in different types of noisy environments (next to a rushing stream, or when lots of crickets or cicadas are calling around them) use these two strategies differently in different noise contexts.