The Hawaiian hoary bat prefers a solitary life and typically leaves its roost just before the sun sets and returns before the sun rises. It prefers to feed on insects flying over streams, bays, or along the seacoast, and it can eat up to 40% of its own body weight in a single feeding. Little is known about its reproductive behavior, but females have been known to give birth to twins during the summer months.

The current population is unknown. Causes of decline include habitat loss, pesticides, predation, and roost disturbance. The US FWS has developed a research and recovery program to learn more about the species and to restore a healthy population.