Fig 2.

(a) Speed distribution of surface fish as a function of group size. The halo around each curve corresponds to one standard error on either side of the mean. A sharp peak near zero indicates fish are not moving. The area under the peak is the fraction of the time the fish are not moving. (b) Fraction of time spent moving faster than 1 cm/s (“active”) as a function of group size. Cavefish are almost always moving (they are active > 99% of the time in every trial regardless of population or group size), whereas surface fish are less active when they are more isolated (linear regression slope 0.02 cm/s/fish, N = 52, p = 0.007). (c) Same as (b), zooming in on the cave populations.