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Naturalist Notebook 23 June to 29 June

June 23rd  was bright and clear and we headed east of Stellwagen Bank to an area known as “The Triangle.”  This area is a frequent hotspot for humpback whale activity, and sure enough, we encountered several of them, including Thread, Sirius, and Garland. 





This week, our interns began their summer stint on the Dolphin Fleet.  Two of our interns, Daniel Alberto Veras Mena, and Peter Sanchez Calderon are visiting from the Dominican Republic, where they are studying ecology related to Santuario de Mamíferos Marinos de la República Dominicana (SMMRD—Marine Mammal Sanctuary of the Dominican Republic).  This is an area significant to our study of humpbacks in the North Atlantic because this sanctuary, located about 50 miles north of the Dominican coast, includes an area known as the Silver Bank, or Banco de la Plata, where our humpbacks reside during the winter months.  The Silver Bank represents the largest breeding ground for humpback whales in the world, with up to 3,000 individuals present each year to participate in courtship behaviors, mate, and give birth to their calves!




Interns Peter and Daniellearn data collection techniques from Dolphin Fleet naturalist, Mike


The Marine Mammals Sanctuary of the Dominican Republic is the largest marine mammal sanctuary in the northern hemisphere and was also the first established marine sanctuary in the Caribbean region.  It is considered a “sister sanctuary” to Stellwagen Bank National Marine Sanctuary, which is more often than not the destination of Dolphin Fleet Whale Watch excursions.  This is significant because these sanctuaries mark the endpoints of a 1,500 mile migration. This partnership is, in fact, the first partnership between sanctuaries in different countries to protect a migratory marine mammal on either end of its range.


East of Stellwagen Bank, on June 24th, dozens of whales congregated to take advantage of the schools of sand lance that had converged on the area.  Humpbacks like Anvil, Tear, Tongs, and Apostrophe were kickfeeding, using their strong, muscular tails to stun schools of fish before lunging through them.  Meanwhile, Sloop, another humpback, used another feeding strategy to corral fish.  Using her chin, she would slap the front, ventral side of her body on the water and then lunge through the resulting bubble cloud. 


Though humpback whale feeding behaviors tend to be obvious, occurring at the surface, it is less common to see obvious finback whale feeding behaviors.  Today was an exception.  On our afternoon trip, passengers on the Dolphin VIII encountered finback whales feeding with such force that they created a wall of sea foam and spray as they lunged through schools of sand lance. Look closely at the photos below and see if you can spot the sand lance leaping as the finback whales lunge through the school of fish.




Lunging finback whales


Unlike humpback whales, finback whales will roll 90 degrees to either side as they lunge through pockets of prey.  The suggested reason for this feeding behavior has to do with the shape and the size of the whale’s mouth as well as the distribution of the prey in the water column.  As the finback whale rolls to its side, it is able to maximize the amount of fish engulfed with each mouthful, as it is able to capture the fish that may be slightly lower in the water column. 


The morning of June 25th  was an unusual one, in that Dolphin Fleet whale watchers were treated to a high number of tail breaches from some of our humpback whales.  During a single trip, we observed Whisk, Eden, Milkweed, and one of our unidentified humpbacks throwing their huge, muscular tails and tail stalks out of the water, and hurling them back down.  Some passengers wondered whether it was a beacon of bad weather, as sure enough, the wind picked up considerably during the afternoon’s trip.




Eden tail breaches


For unknown reasons, we sometimes tend to see more breaching during windy weather and rougher seas.  Perseid’s calf was observed breaching, or completely jumping out of the water, repeatedly.  Some scientists have suggested that perhaps the increased incidence of breaching during stormy seas has to do with the whales having to expend more energy to move through the water or to come out of the water to breathe.  In the photo below, notice how Perseid’s calf lunges speedily through the water.  This is what we call a “wind-up”, or an accelerated dive which precedes a breach.  




Perseid's calf prepares for a breach


June 26th was an exciting day as we were able to visit some of the longest-returning humpbacks to Stellwagen Bank.  Most exciting of all was a sighting of a female humpback named Salt, who was traveling with another female named Cardhu.  Salt was the first Gulf of Maine humpback to officially receive a name.  Because of the white markings on top of her dorsal fin, a Dolphin Fleet Whale Watch captain, Aaron Avellar, named her Salt in 1975.  Salt has been returning to Stellwagen since then, and last year she returned with her tenth calf, a whale named Soya.  All of Salt’s calves have names related to Salt in some way, such as Crystal, Thalassa, and Mostaza, which is Spanish for Mustard.  In 1976, a whale was observed traveling with Salt, and Captain Avellar named this whale Pepper.  Pepper has also been seen this year with her ninth calf.  


The evening trip ended on a high note with as a whale named Banyon repeatedly breached for passengers aboard the Dolphin VII.





The next morning, on June 27th, Banyon, apparently worn-out from the exciting behavior of the previous night, remained nearly motionless at the surface with another unidentified humpback.  Because whales are voluntary breathers, they don’t sleep the way other mammals do.  Because dolphins in captivity are known to sleep with half of their brains at a time, resting one hemisphere while using the other to regulate respiratory activity, scientists have suggested that perhaps this translates to whales in the wild.  Humpback whales are sometimes, particularly after large bouts of feeding or other high-energy activities, observed in a behavior called logging, where they rest nearly motionless at the surface, only moving slightly to breathe every so often. 


After heading north to find more active whales, we came across Trident, a female whale born in 1993, feeding at the surface.  Look closely in the picture below and it is possible to see the baleen plates hanging down from Trident’s upper jaw.  Baleen is made of plates of keratin, which is the same protein in your hair and fingernails.  Baleen plates are embedded in the upper jaw of thirteen species of whale, situated in their mouths instead of their upper teeth.  Baleen whales lack teeth entirely.  Instead, as these 600 to 800 plates of baleen hang parallel to one another in a whale’s mouth, they help the whale separate food from seawater.  Humpback whales, for instance, engulf enormous volumes of food and water, the latter of which they push back out into the ocean by way of the narrow gaps between each pair of baleen plates.  Meanwhile, their prey becomes trapped in the bristly surface of the baleen, which forms a thick mat.  



Trident feeding


Later in the day, we were surprised to see Banyon at it again, breaching again and again. After a morning of rest, Banyon was ready to resume the activities of the previous evening!


On June 28th whale watchers had several fascinating experiences involving humpback whale calves.  First, as we encountered Nile, a humpback born in 1987, and her calf, we noticed that the calf was traveling along side its mothers, but alternating the side on which she surfaced.  This surfacing pattern indicates that the calf is probably nursing.  As mammals, all species of cetaceans nurse their young.  In the case of the humpback whale, that calf is going to be feeding on its mother’s milk for approximately the first 6-8 months of its life, as it gradually weans and learns to feed.  Feeding on its mother’s rich milk, a calf might gain up to 100 pounds per day!


Later, passengers on the Dolphin VII were treated to a close boat approach from Rune’s calf.  Having spent much of their lives in the proximity of whale watch boats, humpback whales do not seem to be concerned about our presence, and often, they will bring their curious calves over to the side of stationary whale watch boats.  While around whales, we turn off our propellers, but keep our generator running.  This allows the whales, who are very acoustically oriented, to know exactly where we are when we are near them, and often they will want to investigate the source of the sound.


On June 29th, we were especially excited to see three humpbacks, Barb, Pipette, and Division, all breaching together.  The groups that humpback whales form tend to be small and unstable, meaning that associations between humpback whales don’t tend to last more than a few hours or so, though exceptions have been observed.  As expected, however, Pipette was sighted later in the day in the absence of Barb and Division. 








One notable change to our environment this week has been the shifting of the Boston Shipping Lanes.  As Stellwagen Bank is a multi-use sanctuary, it is not uncommon to see merchant ships, tankers, and other large vessels traversing the sanctuary.  However, in response to data on whale population densities, this shipping lane was shifted to the north in hopes of reducing whale mortalities as a result of ship strikes.  Complete article



Additional photos of whales mentioned in this week's Naturalist Notebook