Figure S1. Entrance and exit arenas at the ACO climate tunnel model (KT 500). (a) Arena at the tunnel entrance (trial 1, April 2012). Note the acclimation chamber. (b) Arena at the tunnel exit (trial 1). (c) Arena at the tunnel exit (trial 2, October 2012). (d) Infrared cameras installed in the entrance arena and in the entrance tunnel unit. Note the temperature data logger L1 next to the camera in the entrance arena and the raised acclimation chamber.

Figure S2. Probability (means and BCIs) of tunnel usage among three frog species.

Figure S3. Mean air temperature (°C) (BCIs) at the four data logger positions in the tunnel, averaged over 10 nights in April and 7 nights in October 2012. L1 recorded ambient temperature inside the entrance arena, whereas L2, L3 and L4 were positioned at 1, 6 and 12 m from the entrance unit, respectively.

Figure S4. Mean light level (lux) (BCIs) recorded along the tunnel, averaged over 2 days in October 2012. The first recording was taken from the rear of the entrance unit. Only one recording was taken at 11 m, so no BCIs are shown.

Table S1. Morphometric measurements recorded for three frog species used in the experimental runs. Bayesian credible intervals (95% BCIs) are represented by the 2.5th and 97.5th percentiles.

Table S2. Description of travel times for frogs that entered the under-road tunnel. Times were taken to the nearest minute where no seconds are provided. Travel speeds were calculated by dividing travel time by 12.

Table S3. Mean air temperature and relative humidity recorded at four data loggers during the experimental runs.

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