After an incubation period of 12 to 16 days, E. hyllebergi hatchlings emerge in a planktonic state with a visible internal yolk sac.

The female then shortly sinks down to the substrate and dies between one and four hours after depositing her final egg capsule.

[5] The mantles, heads, and arms of Euprymna hyllebergi are covered in chromatophores which are pigmented cells that can expand and contract.

Male and female bobtail squid have two tentacles that are longer than the arms and are used for capturing prey.

[9] Male bobtail squid have an extra arm called the hectocotylus which holds and transfers spermatophores to females.

When beginning to burrow into the sand, E. hyllebergi use a mix of rocking their mantles, fin beating, and water jetting to dig their way beneath.

To completely bury themselves below, they sweep their third arm backwards to collect sand grains and place them over their heads.

As a form of defense, E. hyllebergi can discharge ink which then confuses and distracts predators, allowing them time to escape.

While swimming, E. hyllebergi are able to camouflage through disruptive coloration which occurs when the mantle becomes transparent with visible brown spots.

[5] During the day, Thai bobtail squid hide under sand coats and burry themselves to avoid being seen by predators.

Euprymna hyllebergi are found in the eastern Indian ocean, specifically in the Andaman Sea off Thailand.