Hi Nikola,

This is a very interesting topic. I first noticed this phenomenon when on a field trip to Thailand in June, 1995 with my then graduate student Thom Ludwig and my then post-doc, Jakob Christensen-Dalsgaard. We saw several females of Polypedates leucomystax toe tapping on the dense vegetation on which they were perched. We reported this in several publications, including these:

Narins PM (1995) Comparative aspects of interactive communication. In: Active Hearing (Å Flock, D Ottoson, M Ulfendahl eds.) Elsevier Science Ltd, Oxford, UK 363-372.

Narins PM (1995) Frog Communication. Scientific American 273: 78-83.

Narins PM (2001) Vibration communication in vertebrates. In: Ecology of Sensing (F Barth, A Schmidt eds.) Springer-Verlag, Berlin 127-148.

Christensen-Dalsgaard J, Ludwig TA and Narins PM (2002) Call diversity in an Old World treefrog: Level dependence and latency of acoustic responses. Bioacoustics 13: 21-35.

Narins PM (2019) Seismic communication in the Amphibia with special emphases on the anura. In: Biotremology- Studying Vibrational Behavior II (PSM Hill, R Lakes-Harlan, V Mazzoni, PM Narins, M Virant-Doberlet, A Wessel eds.) Springer-Verlag, Heidelberg pp 277-292.

Hope this helps!

Peter

Hi Nikola, I've taken and carefully reviewed video of Rana aurora behavior. There was no toe tapping, such as in your video. But, what I observed was extensive time nearly motionless, interrupted by lightening quick actions to capture prey. One consideration is if such a behavior as you are seeing might serve to attract prey items. Sincerely, Joanne Schuett-Hames

Hey Nikola, I filled out your survey and would be happy to provide additional details about the several species I've observed toe-wiggling. Many people think that this behavior must be luring, but that is unlikely for several reasons (at least for most species that do it). It is, however, of interest as the type of behavior (intention movement) that can evolve into luring, as it has in Ceratophrys. Perhaps Incilius alvarius also uses its toes to lure, but in the smaller species it appears to have either no function or a scaring function, whereby an insect that has stopped moving is prompted to begin moving again). The papers I've written on luring in snakes can be found on RG, but I have given this topic a lot of thought since those papers were published.

It seems likely that toe-based behavior has different functions in different species. That is the really interesting pursuit, in my view. The unsubstantiated suggestion that this behavior is some kind of intraspecific signaling seems doubtful to me--mostly because of the contexts in which it is performed--but the interesting thing is in looking at how the purposeless behavior evolves (is captured by natural selection) into behaviors with utility. Unfortunately, there are a lot of speculative and unsophisticated suggestions out there about this behavior. The truth will be found in a rigorous experimental approach, so I'm glad to see that you have an interest in pursuing the subject. If there's anything I can do to help, let me know.

Hi Nikola,

We view toe-tapping as a signalling behavior which uses substrate-borne (seismic) waves propagating from the frog to another individual. All frogs tested so far are extremely sensitive to substrate vibrations- in fact they are more sensitive to seismic signals than any other vertebrate (see Narins PM and Lewis ER (1984) The vertebrate ear as an exquisite seismic sensor. J Acoust Soc Am 76: 1384‑1387).

Dear Nikola,

Thanks to Peter Narins we now have this nice book chapter on Biotremology and maybe that and your project will help us discover that toe-tapping is widespread in amphibians. One of the main problems is that it is getting harder and harder to find students that are actually willing to do extensive fieldworks, including ethological observations. I sometimes feel really strange supervising PhD students who work on ecological modelling when right behind our campus in southern Bahia, Brazil, we have more than 50 anuran species. Now, during the ongoing pandemic all my students and me are grounded. But if it helps your studies I can advise them to start collecting behavior related to biotremology after we are back in the field. Recently I have been "forced" to discover how programs as Zoom meetings can enrich not only my lessons but also the science my lab members are producing. Starting next week we will be holding weekly meetings at the "Tropical Herpetology Lab" at State University of Santa Cruz. It would be great if you could join one of these meetings and speak about your project, maybe even give some advise how to collect this data.

Greetings,

Mirco