On May 2nd we sailed out to Cape Cod Bay excited to see what the day had in store. Our first sighting was 6 harbor seals that were hauled out on Long Point. Shortly after leaving the harbor seals, we came across various cetaceans, including 13 humpbacks, 5 fin whales, 5-6 North Atlantic right whales and 115-230 Atlantic white-sided dolphins! Unlike mysticetes (baleen whales) that are solitary animals, odontocetes (toothed whales) such as Atlantic white-sided dolphins, are highly social and are commonly found in pods, which are groups of related individuals. White-sided dolphins are frequently observed in group sizes of a few individuals to several hundred. It is always exciting to see dolphins in Cape Cod Bay, as sightings are often not too common. The Atlantic white-sided dolphins were probably feeding on small schooling fish such as herring, small mackerel, gadid fishes (codfish and their relatives), smelts, hake or sand lance. The dolphins locate their prey by using echolocation, which is the production of high-frequency sound waves and reception of echoes to locate objects as well as to investigate adjacent habitats. Current abundance estimates for Atlantic white-sided dolphins yield 40,000 individuals in the western Atlantic and a few hundred thousand in the entire Atlantic.
Humpback sightings included; Ganesh & calf, Klondike, Ventisca, Terrace, Reflection & calf, Rune and Shoreline!
Atlantic white-sided dolphin, leaping
The Portuguese Princess left Provincetown harbor with bright skies and glassy-calm seas on May 3rd. Cape Cod Bay was alive with various forms of marine life and so we only traveled as far as Wood End. Marine mammal sightings included 1 North Atlantic right whale, 7 humpback whales, 6 fin whales and 350-450 Atlantic white-sided dolphins! One of our humpbacks was a whale named Monarch, the offspring of Dome (born 1998). Humpback whales are gendered in several different ways. Female humpbacks can be identified in the field first by their size, as adult female humpbacks are often larger than adult males. Second, reproductively mature females are often seen with a calf and third females have a hemispherical lobe that can be identified through opportunistic photographic documentation. Monarch is one of the many Gulf of Maine humpbacks that have yet to be gendered. After leaving Monarch we found several humpbacks that were engaging in active behaviors such as flipper-slapping and rolling. We identified Eraser, Deneb, Shoreline and Reflection & Calf.
On May 4th we had a wonderfully diverse trip, with 5-6 North Atlantic right whales, 14-15 humpback whales, 11-15 fin whales and 100-200 Atlantic white-sided dolphins! It appears as though the fin whales were in foraging mode as several of the whales sighted were traveling randomly. Once fin whales locate their prey they often will break from their random travel pattern and begin circling. Its thought that circling may confuse or coral fin whale prey (sand lance). Later in the day we came across a group of active North Atlantic right whales that appeared to be in a surface-active group. Flipper slapping, spy-hopping and rolling are behaviors that are characteristic of surface-active groups. Sometimes this social behavior results in mating, whereby a female right whale will call out to males in the surrounding area and allow the most fit male to mate with her—a process that can go on for quite some time! Towards the end of our trip we encountered several curious humpbacks and were able to get close looks at a female named Ventisca (blizzard).
Ventisca, dorsal fin
We left Provincetown aboard the Dolphin VIII with light rain and fog. Despite our less than ideal sighting conditions we had an exceptional trip with 9-12 humpback whales, 10 fin whales and 75-150 Atlantic white-sided dolphins! As a general trend, the whales appeared to be in search of prey as the fin and humpback whales were all traveling randomly. The whales were most likely in search of sand lace (Ammodytes americanus), which are small schooling fish. Female sand lance spawn only once a year, leaving 23,000 eggs in Cape Cod Bay during December and January. The fish hatch once the water drops to a frigid 48 degrees or lower. The fish larvae will remain in the plankton stage for approximately 1-3 months and will grow around a half inch per month. Sand lance can reach 6 inches (five years old), however, the majority of the population consists of younger fish. Sand lance get there name because they burrow into the sand to prevent predation. The fish are thought to rest at night and hibernate in the winter months. Finally, when spring comes the sand lance will leave the sea bottom to feed on zooplankton, preferably calanoid copepods which are almost microscopic crustaceans. Sand lance populations fluctuate over time, as changes in water temperature and circulation are known to adversely affect the population. Fluctuations in the number of predators also affects the sand lance population, as increases in herring and mackerel in 1986 and 1987 limited the number of sand lance in Cape Cod Bay and Stellwagen Bank.
On May 6th we sailed out to Cape Cod Bay with bright skies and fair seas. We had incredible whale sightings, with 23 humpbacks and 8 fin whales! Several of our humpbacks appeared to be very curious of our vessel. Backgammon was particularly intrigued by our presence and swam around our boat for over 10 minutes! As Backgammon swam around our boat we were able to get great looks at the whale’s blowholes and tubercles. Tubercles are hair follicles located on the top of humpback whale’s heads. Some researchers believe that humpbacks may be able to use this hair to assist in prey detection, similarly to how a cat uses its whiskers to detect close objects. Shortly after leaving Backgammon, three juvenile humpbacks became interested in our boat. One of the curious juveniles even started to flipper-slap!
Curious humpback whale