Figure 8: Physiological response of a single pair of crayfish. (a) “In water”. (b) “Out of water”. The dark blue line indicates crayfish one and light blue indicates crayfish two. Each point represents direct counts of each beat over 10-s intervals and then converted to beats per minute (BPM). The red dotted vertical lines indicate a physical interaction. The same pair was used in both conditions with multiple days in between each trial.