Orcas, or killer whales as these large cetaceans are sometimes called, are found in all the world’s oceans. Though the International Union for Conservation of Nature considers the species “Data Deficient” on its conservation status list, resident populations are monitored in various regions, and some of these populations are nearing total collapse. The UK’s only known population of resident orcas is facing that threat now.
A Pod of Aging Whales
The UK’s resident orca pod, known as the Hebrides resident orca pod, ranges from the west coast of Ireland to Scotland’s northern and western coasts. It is believed to contain only nine individuals that live in complete isolation from the rest of the northeast Atlantic Ocean’s orca population. It’s not only the fact that the group is so small that has researchers feeling concern; it is also the fact that this pod of aging whales has produced no calves for nearly twenty years. The Irish Whale and Dolphin Group, along with the Hebridean Whale and Dolphin Trust (HWDT) have been studying the group for nearly two decades. There are five females and four males; however, the females are likely post-reproductive.
Besides failure to reproduce, the whales have been unable to recruit new pod members from groups of orcas traveling through waters off the UK coast.
Potential Evolutionary Loss
This group of orcas is unique. Members of the Hebrides resident orca pod are about a meter larger than other orcas. Their eye patch orientation is different, and tooth wear patterns are also distinct. In addition, genetic analysis has indicated that members of this pod are more closely related to orcas from Antarctica than to others traveling through nearby Atlantic waters.
Research focused on the northeast Atlantic orca population suggests that these orcas have completely separate ancestry and a different genetic makeup from their traveling neighbors. Unlike those passing through, which feed primarily on seals and pelagic fish, the Hebrides pod seems to feed primarily upon other marine mammals, including some seals, porpoises, and maybe even minke whales. As all these orcas are important apex predators, scientists are concerned that the loss of the Hebrides pod could cause ecological imbalance between predatory species and prey throughout the region the animals occupy.
For now, scientists are continuing to observe the orca pod from afar. These animals can live to be ninety years old, and the females of the species are known to live longer than the males do. This pod is also being studied by Earthwatch scientists and volunteers, who are focusing on conserving their habitat and learning more about the individuals in the group. Each of the pod’s members has been individually identified and photographed, so when the whales are spotted at various locations, individual orcas can be easily accounted for.
Each year, HWDT collects additional data. While no one can say for certain what happened to other orcas with the same ancestors as the Hebrides pod, it’s clear that these nine animals may be the last of their kind. Though they are treasured and protected, they will almost certainly become extinct.