Measuring athletic performance in post-metamorphic fire salamanders

Abstract

Objective: Athletic performances are dynamic movements that are physically challenging and often predict individual success in ecological contexts. They stem from a complex integration of multiple phenotypic traits-e.g., morphological, physiological and behavioural-that dictate animal survival and individual fitness. However, directly quantifying athletic performances can be particularly challenging in cryptic, slow-moving species or not very reactive in attitude. Here we present and describe a rapid, simple, and low-cost method to measure athletic performance in post-metamorphic individuals of the fire salamander Salamandra salamandra. While extremely reactive during the larval stage, adult salamanders are, in fact, cryptic and relatively slow-moving.

Results: Forcing terrestrial juveniles to swim under standard, albeit ecologically plausible, laboratory conditions, and using an automatic point-mass tracking tool, we were able to measure maximal and average performance indicators of post-metamorphic individuals. This method avoids inter-individual variation in motivation, as it forces individuals to perform at their best. Moreover, with this method, measures of athletic performance will be directly comparable between larval and terrestrial stages, allowing to study the contribution of carryover effects to the wide range of processes implicated in the eco-evo-devo of athletic performance in salamanders.

Keywords: Athletic performance; Fire salamander; Salamandra salamandra; Swimming.

Fig. 1

A The fire salamander Salamandra salamandra (Photo: Grignani G.). B The arena used for the swimming test (salamander is not in scale). C Swimming force profile of an individual as a representative example (black line: raw data; grey line: moving average)

Fig. 2

Violin plots of the measured variables. Horizontal lines display the mean value, and vertical bars show the 95% confidence interval. A Weight (g); B Max speed (cm/s); C Mean speed (cm/s); D Max swimming force (N); E Mean swimming force (N); F Time to reach the edge (s). The graphs were drawn using the web app PlotsOfData [44] and the software Canvas 11 (ACD Systems of America, Inc.)