Naturalist Notebook 2 June to 8 June
Tue 12 Jun 2007 - Filed under: Main Page — admin
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June 2nd’s afternoon trip experienced a wide variety of humpback whale behaviors.  Buzzard, one of our humpbacks, was observed actively feeding, kickfeeding and blowing bubble nets.  Meanwhile, other humpbacks in the area rested at the water’s surface, only slightly moving every few minutes to take a breath.  Because whales are voluntary breathers, they’re not able to sleep in the same way other mammals would.  In becoming unconscious, they would forget to breathe!  Although dolphins in captivity have been known to sleep with half of their brains at a time to overcome this obstacle, scientists are not sure whether or not this is the case with large whales in the wild.  The resting behavior of humpbacks and other large whales is called logging, as the sedentary bodies of a large whale resembles a log floating on the surface of the water.

 

 

Humpback whales logging

 

The dense fog and limited visibility made June 3rd’s whale watch a little bit more challenging for our captain and crew.  Sometimes, just listening for the loud exhalation of a whale can be the best way to find whales in pea soup-like fog, and today, the sharp listening skills of our passengers and crew paid off.   Pressurizing the air in their lungs is one of the ways whales conserve their oxygen, so when that pressure is released during an exhalation, the resulting noise is unmistakable.  Using our ears and our limited visibility, we finally located our first humpback on the Southwest corner of Stellwagen Bank. 

 

Sometimes the most memorable whale watches occur on days with less than ideal weather, and certainly, today was one of these days.  As soon as we found Circus, a young humpback whale, it became incredibly active, displaying some of the most dramatic humpback whale surface behaviors, including flipper slapping, lobtailing, and even full spinning head breaches.  Circus was named for the marks on the underside of its fluke, which resemble the attractions of a three ring circus, including a shape that looks like someone being shot from a cannon!  Certainly with this acrobatic behavior, Circus was living up to its name. 

 

 

Circus lobtailing

 

After canceling June 4th’s trips due to high winds and rough seas, we weren’t sure what to expect for June 5th’s trip.  Our whalewatch vessels visit such dynamic ecosystems that they can drastically change over the course of a day.  The most dramatic change that we noticed was the return of the greater shearwaters.  Greater shearwaters are gull-sized birds which spend most of their lives at sea.  Like our humpback whale population, greater shearwaters summer in the North Atlantic to take advantage of the highly productive ecosystem and abundant food.  We often find them in the same locations as our humpbacks because they both especially like to feed on sand lance. 

 

Greater shearwaters, however, travel an even greater distance than our humpbacks during their migrations.  Greater shearwaters are transequatorial migrants, which mean that they traverse the equator over the course of their winter travels.  During our winter season, greater shearwaters nest and breed on the rocky islands off the coast of Argentina.  This is the only time that they spend on land.  The return of the greater shearwaters are a sign that summer is here at last. 

 

June 6th brought typical Cape Cod weather, which seemed to change every hour.  The morning trip experienced six foot swells and overcast and rainy weather.  By the evening trip, the sun had emerged and the seas had calmed to a flat, glassy plane where spouts could be heard and dorsal fins could be seen emerging from the water from many miles away. 

 

After finding three different species of baleen whale during the morning trip, Captain Steve Milliken noticed something strange in the water.  “Could that be a basking shark?” he wondered.  Basking sharks usually are not found until later in the summer when the water temperature is a bit higher, however, this particular animal was early-season surprise for us. 

 

 

Basking Shark

 

Basking sharks have a menacing appearance, reaching lengths of over thirty feet, but they are not a threat to humans.  Basking sharks have a filter-feeding apparatus in their mouths which is not unlike the baleen in a whale’s mouth, which they use to filter and consume zooplankton.  Like the right whale, the basking shark acquires most of its nutrients from copepods, and sure enough, when we performed a plankton tow near the feeding shark, the water was thick with these orange, shrimp-like crustaceans.  The similarity between the sharks’ filter feeding apparatus and the whale’s baleen is an example of convergent evolution, which refers to instances in which very unrelated species acquire similar anatomical structures to deal with similar environmental conditions.  Other examples of convergent evolution in nature include bird and bat wings, and the webbed feet of various aquatic animals.

 

 

Passengers observe a basking shark from the Dolphin VIII

 

 

 

June 7th- After several days of relatively quiet behavior, our humpbacks began the day with a feeding frenzy.  At least 27 humpbacks, including Weave, Percussion, Tracer, Grommet, Grackle, Nimbus, and Ember were blowing bubble nets to corral fish, and swallowing hundreds of sand lance with every expansive mouthful.  Humpback whales are opportunistic feeders, and are not known to favor one time of day over another for feeding.  For that reason, we are always grateful to be able to find them as they perform their dramatic feeding behaviors. 

 

 

 

Humpback whales blow bubble nets while feeding

 

By the evening’s trip, the feeding had ended, but the excitement continued as a humpback whale named Ventisca curiously approached the Dolphin VIII, even lifting its head out of the water to try to see us more clearly!  Ventisca is the Spanish word for blizzard, which describes the unusual white pigmentation on its dorsal fin. 

 

 

Ventisca's white dorsal fin

 

 

Ventisca sneaks a peek at Dolphin Fleet whale watch passengers

 

On June 8th we came across a smaller humpback whale that appeared to be a juvenile.  As adults, humpbacks can reach lengths of almost 60 feet, but it can take them 8-10 years to reach full maturity.  As they get larger and acquire more blubber, they fluke with more and more consistency; however, younger whales sometimes fail to display their flukes as they dive, making them more difficult to identify as individuals.  One activity on the Dolphin Fleet is the “Blubber Glove” experiment, where passengers can experience the insulating power of whale blubber, using cooking fat as a substitute for the real substance, of course.

 

 

The “Blubber Glove” experiment

 

Later, we came across one of our most easily-identifiable individuals.  A female humpback named Nile with her third calf.  Although they were logging, or resting at the surface without diving, we immediately knew it was Nile due to her distinct, hook-shaped dorsal fin. 

 

In the afternoon we had another encounter with a juvenile humpback, and this one seemed just as interested in us as we were of it.  As the Dolphin VIII drifted with Highland Lighthouse in Truro looming in the background, our humpback whale approached the boat, lifted its head to look at us, and swam back and forth underneath the boat, possibly investigating the sound of our generator.  Meanwhile, a harbor seal appeared next to the boat to get a closer look at us as well.  This close encounter with several of the planet’s most fascinating creatures marked an end to another fantastic week of whale watching. 

 

 

Harbor Seal

 


Naturalist Notebook 26 May to 1 June
Mon 4 Jun 2007 - Filed under: Main Page — admin
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During the weeks leading up to May 26, we had witnessed intense surface feeding behaviors from our summer population of humpback whales, and we wondered whether or not they would keep it up. Sure enough, we soon came across eight humpback whales feeding on the Southwest corner of Stellwagen Bank. Because feeding behavior often happens near the surface, we don’t always see the fluking dives that we see when whales go for deeper dives. Humpback whales are generally identified as individuals based on the black and white patterns on the underside of their tail or fluke, but when they don’t raise their tails in a fluking dive, we have to rely on other methods. The white scar running up Abrasion’s tailstock easily identifies this whale, even without the fluke pattern, but what about the others? Fortunately, the size and the shape of the dorsal fin can also be a reliable indicator of a whale’s identity. Note the difference in the size, shapes, and markings on the dorsal fins pictured below.

Ember’s Dorsal Flounder’s Dorsal Tunguska’s Dorsal

May 27 brought us more feeding humpback whales and several long, slender finbacks. At one point during the trip, passengers started to ask about the smaller dorsal fin that periodically appeared and disappeared among the feeding humpbacks, and wondered whether or not they were seeing dolphins. This creature turned out not to be a dolphin at all, but rather, a smaller type of baleen whale—the minke whale.

Smallest of the baleen whales in Cape Cod waters, this seemingly small whale is actually about 20 feet (6.1 meters) long! The Minke whale is also known as the little piked whale, because of the pointed snout visible when the whale first surfaces. In the waters off Cape Cod, Minkes are sighted year round, yet, little is known about their lives. Sightings on Stellwagen are primarily of one individual or small groups of two or three. Unlike other species in the area, it is rare to see mothers with calves. Some researchers speculate that the Minkes of Cape Cod are primarily juveniles.

Abundant in number world-wide, Minkes are the most heavily hunted baleen whale. Despite a moratorium on commercial whaling, over 1400 Minkes are killed each year in commercial hunts off Iceland, Norway, in the North pacific and the Southern Ocean Whale Sanctuary.

On May 28, as is standard, we advised our passengers to participate in the intial whale-finding mission by scanning the horizon and looking for a “spout”— the visible exhalation of a whale. This technique is often our best bet for finding whales on days with moderate to high visibility. Today, however, this became unnecessary as soon as we got to the Southern edge of Stellwagen Bank. The unmistakable body of a humpback whale leaping and spinning out of the water was visible above the waterline, and was soon followed by a lingering mound of whitewater from the whale’s impact with the water surface. A breach!

Normally, it’s unlikely to see a breach at all, which is why we could hardly believe our eyes when we saw not one, not two, but three humpback whales all breaching side-by-side! Tongs, Abrasion, and Flounder, named for the distinct markings on their flukes or tails, continued to breach synchronously as we watched, awestruck.

Why whales breach in the feeding ground is still unknown; however, the fact that these three humpbacks were doing so in such proximity to one another made us consider how little we know about the social structure of these mysterious creatures.

On May 29 we returned to the southern portion of Stellwagen Bank where we came acrossBuckshot and Trident, two humpback whales who brought calves back to Stellwagen Bank last year. Having a calf tends to be a two year commitment for a female humpback, as the gestation period and the time that the calf spends in close proximity to mom each last approximately a year. For this reason, a two year calving interval tends to be standard for a healthy, mature female humpback, although a one year calving interval is not unheard of.

Trident

To our current knowledge, there is no way to tell whether or not a female is pregnant with the naked eye—only hormonal analyses will suffice. Therefore it is possible that next year, either of these whales could come back with another calf. However, it is important to keep in mind that giving birth to a calf is an enormous energetic investment, and in doing so, the female might lose up to 1/3 of her body weight. These females, even more so than the other humpbacks, are especially concerned with acquiring the appropriate amount of calories during their summer feeding season.

Buckshot and Trident’s respective calves have since left their mothers sides and are now on their own to find food for the summer season, but as humpback whales tend to return to the same feeding ground their mothers brought them to in their first year of life, we are hoping to see them on their own this summer.

May 30 Was as an ideal day for a whale watch. The light and variable winds made for calm, glassy seas, and whale watch passengers were clearly enjoying basking in the sun on the upper deck of the Dolphin VIII. Once we got to Stellwagen Bank, the productivity of the ecosystem was immediately evident. Humpback whales and birds alike were busily feeding on sand lance, which is a small schooling fish found in the billions in Stellwagen Bank. It is frequently used as a bait fish, but it also happens to be the favorite food of certain types of birds and whales alike.

As humpback whales displayed their variety of feeding behaviors—bubble nets, kickfeeding, and bubble clouds—herring gulls flew low over the water causing the fish to leap out of the water in a cascade of miniscule, shimmering splashes. The pattering sound of the fish hitting the water as the whales loudly exhaled echoed off the stillness of the water as we watched striped bass swim under our bow. A copepod-rich plankton tow performed at that moment revealed to us yet another important component of the predator-prey ecosystem interactions of this highly productive area.

On May 31, the Southern edge of Stellwagen bank was the place to find active humpbacks, including Trident and Circus. A splash in the distance led us to a lobtailing humpback, who, on closer inspection of the fluke, turned out to be an individual named Habeñero. In general, humpback whales are named after a distinctive marking on their fluke. Indeed, the black shape on this whale’s left fluke closely resembles a habeñero pepper. However, in this case, the name is closely related to the whale’s lineage. Habeñero was born in the year 2000 to a whale named Pepper. Pepper herself was named because she was frequently seen in the presence of Salt, who was the first humpback to officially receive a name in the Gulf of Maine.

Habeñero

June 1 provided an ideal photo opportunity with a humpback whale breaching with the Pilgrim Monument of Provincetown looming the background. This was a striking reminder that these whales are experiencing their drastically different lifestyles in our very backyards!

A humpback whale breaches with the Pilgrim Monument in the background

The backdrop of Provincetown as seen from the whalewatching boat also highlighted the dramatic shift in how visitors and residents of Provincetown view the nearby whale population. Once home to a major whaling fleet, Provincetown is now a very conservation-minded community, and is home to a whalwatching industry which emphasizes the appreciation and protection of our precious marine resources.

Students keep track of the trip’s sightings