An international environmental group filed a lawsuit Wednesday in federal court in Washington, D.C., that aims to force federal agencies to put in place overdue endangered species protections for Hawaii’s false killer whales.

The whale, which grows up to 20 feet long and can weigh 4,900 pounds, is a larger, darker-colored member of the dolphin family that lives close to the shorelines of the main Hawaiian Islands. The population in the islands is described as insular because it has become genetically separated from the rest of the species, according to the Natural Resources Defense Council.

The population, which consists of an estimated 150 whales, was placed on the federal endangered species list in 2012 following a petition filed by the NRDC.

Giulia C.S. Good Stefani, a staff attorney with the NRDC’s Marine Mammal Protection Project, said federal agencies have failed to promptly put in place measures to protect the whale’s habitat. The Endangered Species Act requires protecting habitat as a means to ensure that an endangered population can stabilize and recover.

“The species is in grave danger of going extinct because of this delay. Their survival depends on getting their habitat — their home, really — protected. It’s past time for the government to step up and fulfill its duty,” Stefani said.

The U.S. Department of Commerce, National Atmospheric and Oceanic Administration and National Marine Fisheries Service are responsible for designating critical habitat protections.

Stefani said while the agencies contend there is not sufficient information to designate a critical habitat area, the nonprofit maintains that more than enough research and observation has been done and the designation is about a year overdue.

“The critical habitat designation centers around where the whales spend their time and which areas are critical for them to recover,” Stefani said. “That info is out there, a lot of research has been done. We think the agencies could designate now.”

Currently the false killer whales face threats ranging from reduced prey caused by overfishing to injury due to fishing gear and toxic contamination. According to the NRDC’s 2010 petition for an endangered species listing, there is a 50 percent probability the whales will become extinct in the next 75 years.

Stefani said designation of a protected habitat area could also help shield the whales from Navy activities, such as mid-frequency sonar use, which is linked to cases of mass strandings of whales.