The calf was seen in Puget Sound off the coast of Washington this week, adding to the spate of new baby orca arrivals in the area over the past few months. Spotted by scientists from the National Oceanic and Atmospheric Administration, the calf still had body markings called fetal folds and a bent dorsal fin, suggesting he or she had just been born.

This year has seen a great one for an endangered population of whales who live in the area - four new calves were spotted over just three months. The births are huge signs of a hope for a population many feared was headed for extinction.

But the calf spotted this week is part of another, lesser-known population of wild whales: "transient" orcas - a genetically distinct group that hasn't bred with resident whales for some 10,000 years. These whales, also known as Bigg's orcas, roam over large areas of coastal ocean and, unlike the fish-eating resident orcas, they hunt marine mammals like seals and sea lions.

They have slightly distinct looks from other orca populations: transient orcas generally have pointed dorsal fins, and their saddle patches (the gray marks on their sides and behind their fins) are generally farther forward. The transient orcas of the Pacific northwest swim in small, female-led pods off the coast Washington State, British Columbia and Alaska. Like tourists, they pop into areas like Puget Sound for a short stay every once in a while.