Tim Gunther is sketching a squid. The mollusk emerging in pencil on tracing paper has been caught in the act of depositing two tall, cylindrical egg cases into the sand at the bottom of the image.

The day a male spear squid hatches determines which mating tactic he will use throughout his life, according to new research. Spear squid (Heterololigo bleekeri) that hatch earlier in the season ...