Concerned scientists are sounding the alarm over the loss of six rare North Atlantic right whales off the Canadian coast in a single month. There are only some 400 of the animals left on Earth, and fewer than 100 of them are females of reproductive age.

The six, including at least four females, were found in the Gulf of St. Lawrence north of New England, reported officials with the U.S. National Oceanic and Atmospheric Administration. Researchers believe at least three of them were killed in collisions with ships. One of them was the mother of eight, grandmother of two and 40 years old when she was found dead from a ship strike.

The whales also die — often excruciating deaths — when they become entangled in fishing gear.

“Honestly, I don’t have the words,” Regina Asmutis-Silvia, executive director of Whale and Dolphin Conservation North America, told The Atlantic in an article published last week. “It’s devastating. There’s now more people working on right whales than there are right whales left.”

The deaths are such a significant toll on the population that researchers fear it will soon be too late to prevent extinction.