In a heartbreaking display of maternal grief, an endangered killer whale swam off the coast of the Pacific Northwest with her dead calf for more than three days.

The mama whale, dubbed J35, is one of a dwindling number of Southern Resident killer whales that live near Washington and British Columbia, Canada.

J35 gave birth to the 400-pound female calf on Tuesday. Less than an hour later, researchers saw her pushing her baby’s carcass up with her nose. She kept the body afloat with her head as she swam 60 to 70 miles each day in strong currents.

It’s not unusual for whales to carry a dead newborn around for a short time, but one researcher said this was the longest display of grief he had seen.

It was the first calf born in three years to the pod, which is at a record-low 76 members, down from 98 in 1995. Researchers fear it may be too late to save the population, which has suffered due to toxins, ship traffic and a lack of food, specifically Chinook salmon, according to the Center for Whale Research.