Heartbreaking moment: an orca mourning the loss of her second calf carries it on her head (photo).

The orca named Tahlequah, or J35, made headlines in 2018 after embarking on what scientists referred to as a "tour of grief." In total, she traveled around 1,600 kilometers while carrying her calf on her head, until she finally let it go. The previous "tour of grief" lasted 17 days, and it seems that the female is repeating her ritual, according to Live Science.

Tahlequah is part of the southern resident orcas, a population currently on the brink of extinction. Since the loss of her first calf, Tahlequah has managed to raise two calves, but now she is once again mourning the loss of her baby. Researchers from the National Oceanic and Atmospheric Administration (NOAA) spotted her with a calf on her head in Puget Sound near Seattle on January 1.

According to NOAA public affairs officer Michael Milstein, this news marks a troubling start, especially for a population that is already vulnerable. It’s important to note that southern resident orcas (Orcinus orca) are listed under the U.S. Endangered Species Act, and for several years, scientists have been working to protect these whales from extinction.

Researchers identify three primary reasons for the decline of the pod:

• insufficient prey — primarily Chinook salmon;
• pollution;
• injuries sustained from collisions with boats.

In a 2017 study, scientists found that nearly 70% of pregnancies among southern resident orcas ended in failure between 2008 and 2014, with a third of these losses occurring late in pregnancy or immediately after birth. Scientists who documented the death of Tahlequah's last calf believe the baby lived no more than a week.

The newborn calf was first spotted by citizen scientists on December 20. They also noted that the calf was alive on December 23 and its appearance was not concerning. Tahlequah appeared to be pushing the calf — named J61 — even while it was alive, and although the calf seemed viable at that time, something was amiss. Researchers observed that when the calf surfaced, it appeared to be struggling. On December 31, researchers continued their observations and noted that the calf was missing. At the same time, they observed that the female was pushing something — it was soon confirmed to be the body of her calf.

Researchers state that while this behavior is not unusual, orcas are one of the few species of whales and dolphins known to carry deceased offspring.

NOAA researchers indicate that they will continue to monitor Tahlequah's pod. Despite the year starting with tragic events, scientists remain hopeful for the future of the pod. The good news is that this week, scientists also recorded the birth of a new calf in the pod.