Mostly observed singly, and occasionally in small groups. Feeds mainly on fishes. When stressed or harassed, may secrete a slimy skin toxin, grammistin,. Experiment showed that when confined in small volume of water, this toxin can be lethal to other fish species. (*note) *Note: One D. bifasciatum, 158 mm in standard length, was agitated in 800 ml of seawater for 5 minutes. Five adults of Japanese rice fish, Oryzias latipes, were then placed in this water. They showed immediate motor excitation and died within 15 minutes. Although a fresh- water species, O. latipes, can ordinarily survive in seawater for at least a day.