Rachel Page, STRI Staff Scientist

Co-supervisor:
Luke Larter, Postdoc and STRI Research Fellow

Gamboa

In many taxa, males produce elaborate signals and courtship displays to entice females to mate. Females prefer louder, faster, and longer displays, and these preferences are considered adaptive when male display intensity correlates with the direct or indirect benefits that males can provide to females. Such a correlation often occurs when display intensity is constrained by male physiology, as these physiological constraints provide a concrete route by which display intensity can be informative with respect to inter-male variation in quality or condition. This is especially true for behavioral displays such as vocalizations and courtship dances, which are driven in real time by demanding muscular exertions, meaning display intensity is constrained by the performance limits of male display muscles. In such cases, high performance physiologies are selected for in males as an indirect consequence of female preferences for more stimulating displays.

Though these theories are compelling, empirically linking variation in important male performance capacities to salient variation in display properties has been challenging. This is because identifying exactly which components of complex behavioral displays are salient to females, and which physiological constraints limit elaboration of various display properties, is immensely difficult. Túngara frogs have several strengths that alleviate these issues; we have decades of research on female preferences for different call attributes, and calls are driven by relatively simple muscular contractions of the abdominal muscles. Here we will: i) investigate inter-male variation in the upper limits of signal elaboration (via audio playback studies), ii) investigate how inter-male variation in patterns of airflow during calls correlate with call elaboration levels (via high-speed video of calling males), and iii) investigate whether inter-male variation in performance capacities of the calling muscles predicts variation in airflow rates and call elaboration patterns (via in-situ muscle performance assays). This will be one of the most detailed investigations yet of the mechanistic underpinnings of inter-male variation in courtship signaling behavior.

This project will require some fieldwork (collecting frogs), and much lab work during experiments with collected frogs. The project start date will be around June or July 2026, with some flexibility. The intern will assist in setting up the project, and in conducting the experiments. Data collection will occur at night (likely ~7:30pm-2am), though some daytime preparation work may also occasionally be required. The time commitment expected will vary according to current project demands, but the intern will have at least 2 free days per week.

The intern involved in this project will gain valuable fieldwork and scientific skills. They will thoroughly trained in field biology and bioacoustics techniques. During their time in Panama, they will get hands on experience collecting wild frogs, caring for captive frogs, performing behavioral experiments including audio playback studies, and collecting and processing audio data and high-speed video data.

Though the project described above will be the focus of the 2026 field season, in addition to contributing to this project, there is the potential for the intern to design/implement an independent project. The PI has broad interests in calling/chorusing strategies and the effects of calling interactions on female choice. Thus, if the intern has an idea for a study along these lines in túngara frogs, they would be encouraged and supported to pursue it once the main project is up and running. The PI will provide guidance through all steps of project design, implementation, analysis, and presentation of the results, and will help the intern prepare the study for publication.

In addition to learning through direct experience in the field and acoustic and video analysis, the PI will discuss career advice and training for next steps in the intern’s scientific trajectory. STRI hosts multiple seminars take place each week from a wide range of international visitors, at three of STRI’s nearby campuses: Barro Colorado Island, Tupper and Gamboa, as well as workshops and other learning opportunities that the intern will be encouraged to attend.

Students interested in animal communication and animal behavior are welcome to apply. The intern must be comfortable and sensible around wild animals, be fine with working in tropical weather, and be fine with late nights in the field.

Dudley, R., & Rand, A. S. (1991). Sound production and vocal sac inflation in the túngara frog, Physalaemus pustulosus (Leptodactylidae). Copeia, 460-470.

Fuxjager, M. J., Goller, F., Dirkse, A., Sanin, G. D., & Garcia, S. (2016). Select forelimb muscles have evolved superfast contractile speed to support acrobatic social displays. Elife, 5, e13544.

Girgenrath, M., & Marsh, R. L. (1999). Power output of sound-producing muscles in the tree frogs Hyla versicolor and Hyla chrysoscelis. Journal of Experimental Biology, 202(22), 3225-3237.

Larter, L. C., & Ryan, M. J. (2024). Female preferences for more elaborate signals are an emergent outcome of male chorusing interactions in túngara frogs. The American Naturalist, 203(1), 92-108.

Ryan, M. J., Akre, K. L., Baugh, A. T., Bernal, X. E., Lea, A. M., Leslie, C.,…Rand, A. S. (2019). Nineteen years of consistently positive and strong female mate preferences despite individual variation. The American Naturalist, 194(2), 125-134.