Rare Sightings During October Aerial Survey

Our first sightings involved fishing gear. This is common in the outer track lines of the survey where human presence, although minimal, is tangible. In total, the team recorded 13 pieces of fishing gear on this track line.

As we flew over the blue ocean in search of life, the first confirmed animal sighting occurred when two Cuvier’s beaked whales (Ziphius caviorostris) broke the water’s surface to breathe. Cuvier’s beaked whales are distinguishable by a short, poorly defined beak and a sloping forehead. These were probably young or females because their dorsal fin and back had uniform grey coloration with no scars at all.

The last marine megafauna sighting at the Oceanographer Canyon involved another ocean sunfish. Sunfish spend up to half the day basking in the sun near the surface of the water, which helps warm their bodies after deep-water hunting dives. This surface behavior helps the aerial survey team spot them from the air.

The next four tracklines were relatively quiet. On the second track line, we spotted nine Risso’s dolphins (Grampus griseus) and one ocean sunfish. The third trackline involved sightings of five Risso’s dolphins, two bottlenose dolphins (Tursiops truncatus), two ocean sunfish, and three Sowerby’s beaked whales (Mesoplodon bidens). This was the third species of beaked whales for the day. Sowerby’s beaked whales are distributed throughout the North Atlantic Ocean, but prefer the deep, cold temperate and subarctic waters off the continental shelf edge of the North Atlantic Ocean. They are usually found individually or in small, closely associated groups averaging between three and 10 individuals.

The crossleg (the area between tracklines) was more active. Several small groups of Risso’s dolphins were sighted in the deep waters (more than 2,000 meters/6,560 feet). Group sizes ranged from 1 to 40 for a total of 80 Risso’s dolphins. In the fourth trackline, 10 Risso’s dolphins were sighted. The fifth trackline had two sightings of marine mammals: 40 common dolphins (Delphinus delphis) and five Risso’s dolphins, in addition to sightings of three ocean sunfish and the second Chilean devil ray we mentioned earlier.

Similar to previous surveys this year, Lydonia Canyon was a hot spot. The highest number of sightings and diversity of species occurred here. Seven species of marine megafauna were observed, including more Risso’s dolphins (42), bottlenose dolphins (45), common dolphins (15), and an ocean sunfish (1) as well as striped dolphins (15), fin whales (2), and a humpback whale.

The fin whales (Balaenoptera physalus) were observed inside the shallower waters of the canyon (about 150 to 210 meters). The species had not been spotted in the monument since 2017. The lack of fin whale sightings does not mean that fin whales were not present. Instead, it highlights the importance of continuing to conduct these surveys to ensure that we fully understand the species, numbers of animals, and age groups (e.g., mothers and calves) using this protected area. At this canyon, another first also occurred, the sighting of a humpback whale (Megaptera novaeangliae).

Their scientific name is derived from the Greek words “mega” meaning large and “pteron” meaning wing (referring to their long pectoral flippers, which are one-third of their total body length), and “novaeangliae” meaning New Englander because they were first described from the waters of New England. Their common name, humpback whale, refers to the small hump under their dorsal fin and the characteristic hunched shape that is clear when they are about to dive. This particular individual had on its body visible patches of white, which represent sloughing or areas of scuffing. Like humans, most whales, dolphins, and porpoises are thought to shed skin continuously throughout the year.

The last half hour of the survey was spent on the eastern side of the Lydonia Canyon, where seven fin whales and 10 bottlenose dolphins were sighted. As the survey ended, after approximately four hours of surveying, the plane began to climb in altitude to head back to Plymouth.

But this adventure could not end without a sighting of the largest of the toothed whales. In water depths of more than 1,040 meters (3,400-plus feet), two sperm whales (Physeter macrocephalus) were spotted as they came to breathe at the surface. It was unexpected and a great way to end the day.