Fig. 1. Counts of intervals since last detection preceding calculated octopus positions
from the 2009 near-continuous tracking within a fixed array (note variable scale in
hh:mm, then days). The left-hand peak indicates that most intervals between retained
calculated positions occurred without a missed ping (tags emit pings at random inter-
vals of 30 s to 4.1 min). The right-hand peak at more than 24 h occurs when octopuses
emerge from hiding (inferred when a disappearance and reappearance at correlated lo-
cations and within the array) and signal propagation returns after being blocked by
rock or other obstructions. See text for details.