NATURALIST NOTEBOOK MAY 5 TO MAY 11

Saturday, May 5 was one of those days that reminds us that we have dozens of whales virtually in our backyard. As we watched humpback whales lunge through enormous schools of sand lance, we were close enough to Race Point beach to see visitors to the Cape Cod National Seashore gazing at the spectacle from shore!

Sand lance in abundance

We were excited to find among our group of humpback whales some new friends as well as some old. Lavaliere is a whale that we’ve been watching since 1994, but until she returned this year with her first known calf, we didn’t know whether or not she was male or female. Pictured below is Patchwork, another whale spotted today, named for the patchwork quilt-like markings on its fluke.

Another identified humpback individual was the 2006 calf of Cardhu, spotted last summer in Stellwagen Bank accompanied by its mother. By studying individual animals over the past 30 years, we’ve learned a lot about humpback whales, including their tendency to display sight fidelity. This means that they tend to return to the same feeding ground that mom brought them to in their first year of life. Based on this trend, it would make sense that this young whale is back in the area!

Finbacks surface feeding

Sunday, May 6 brought on more fin whales than we had seen in the past few days. Fin whales, with their sleek and streamlined bodies, can be a little bit more challenging to watch than other species, as they are known to move in bursts of speed of up to 20 miles an hour! A little bit of patience is well worth it, however. Among the fin whales spotted, we even caught a glimpse of a mother and calf pair! While we know a lot about the migration and calving patterns of the humpbacks, those of the fin whales are not as well understood. Hopefully, the observations of fin whale calves off of Cape Cod in the past few years will provide some insight into the reproductive habits of these mysterious and beautiful creatures.

May 7 was so bright and clear that by the time we got to Race Point Light, where the waters of Cape Cod Bay merge with the waters of the Atlantic Ocean, there were so many spouts on the horizon that we had to decide where to go first. Thick, bushy spouts and large groups of raucous birds towards the northwest suggested feeding humpback whales, so we made that our initial destination.

Despite the obvious size discrepancy, large baleen whales like humpbacks and finbacks have a very similar diet to many marine birds, including gulls and shearwaters. Small, schooling fish including herring, sand lance, and mackerel feed low on the food chain and consequently are very high in energy, making them an ideal food source for whales and birds alike.

Large congregations of agitated birds are sometimes the first indication of feeding whales. Humpback whales in particular tend to use bubbles, generated by either expelled air or by the physical force of their bodies slapping the surface of the water, to scare fish into tight bunches. Once this has happened, they lunge through the fish ball with their mouths wide open, as the pleats on the undersides of their bodies expand to maximize the amount of food that gets trapped in the coarse, hair-like fringes of their baleen.

This is precisely what was occurring when we approached our first two humpbacks, one of whom was a young whale named Thread. Thread and companion were blowing bubble nets, lunging, and then dragging at the surface, meaning they were swimming with their heads above water in order to strain the water in their mouths out between the baleen plates. As they did this, herring gulls swooped down to the frothy water to scoop up any straggling sand lance. One particularly bold gull even landed on top of Thread’s knobby head!

There was no shortage of food for the whales that afternoon. From the upper deck of the Dolphin VIII it was easy to see schools comprised of thousands of sand lance swimming right below the surface, hoping to avoid becoming lunch!

A plankton tow later in the trip revealed high concentrations of copepods—shrimp-like zooplankton about the size of a grain of rice—in the water. Dense concentrations of copepods occur in Cape Cod Bay in the spring, and are the favorite food of the North Atlantic right whale. After dragging up such a dense zooplankton sample, we weren’t surprised to see the V-shaped spouts of two North Atlantic right whales as we headed back to Provincetown.

Maintaining a safe distance from these highly endangered animals, we noticed that they were staying at the surface, their dark, rough, heads just barely visible, meaning that they were probably skim feeding using their long, fine baleen. Having spent the winter months conducting aerial surveys of right whales off the coast of Georgia, I wondered if this was one of the individuals that I had observed from a thousand feet above the ocean a few months prior.

May 8 was windy enough that even the normally calm harbor was dotted with white caps. However, the southwesterly winds had brought warm weather and blue skies, so we left the bay in search of the humpbacks that had been spotted feeding earlier that morning. Any Cape Cod whale watching veteran knows that the whale sightings, as well as the weather, can change dramatically from one trip to the next, so we weren’t too surprised to find ourselves in a completely different seascape from the one experienced on the previous trip.

We stopped the boat at the approximate location of the mornings’ sightings to get a sense of our surroundings. The wind had picked up considerably and every so often a particularly large white cap would momentarily give us hope that there was a spout in the distance. Suddenly, without warning, we saw whitewater from an unmistakable source. Up ahead of us, a whale began lobtailing, or repeatedly slapping its tail and tail stock on the surface of the water. No one knows exactly why a whale would exhibit this behavior, but the thunderous noise the whale’s tail makes as it hits the water suggests that it serves a communication purpose of some kind.

After admiring our lobtailing humpback, whom we identified as Eruption, for a while, we spotted another spout which we went to investigate. As we got closer, the humpback whale dove very rapidly. “There’s the wind up!” exclaimed Captain George. Sure enough, the whale leapt out of the water doing almost a complete turn in mid-air. A full spinning head breach, and every whale watcher’s dream event!

Why would a 45 ton animal that has just spent the last few months without food expend so much energy propelling its enormous body out of the water? This is a question that scientists have yet to answer definitively. Perhaps it’s a way of grooming, aiding digestion, or knocking dead skin or parasites off its body. We seem to see more breaching in rougher seas, so maybe breaching is a way for the animal to deal with these conditions, either as an expression of anguish or a way to move more efficiently through the turbulent water. Maybe it’s a way of communicating (perhaps with the lobtailing Eruption, not too far away?), or maybe it’s just exercise or play. Most likely it is some combination of these reasons that cause this behavior.

Wednesday, May 9 brought on another slew of feeding humpback whales, including a large male named Cygnus. While most of the time, the markings on the underside of a whale’s fluke give us the best indication of the humpback’s identity, Cygnus is easily identified by his large, damaged dorsal fin, providing us with another reminder of how human actions affect our planet’s ocean life. We’ve been watching Cygnus since 1980. Although no one is sure exactly how long humpback whales live, identifying individual whales like Cygnus will give us more of an indication of average life spans as the years pass.

Thursday, May 10 did not, initially seem like an ideal day for whale watching. The fog was so thick as I arrived at the dock in the morning that I couldn’t see the top of the Pilgrim Monument towering over 200 feet above Provincetown. Early in the trip we advised passengers that we would probably be looking, as well as listening for whale spouts. On days of low visibility, we sometimes have to rely on our ears to listen for the “whooshing” sound of pressurized air leaving whale lungs to tell us where the whales are.

Luckily, we didn’t have to do this. Once we reached Race Point Light we could see all the way across the bay to Manomet Point, which is south of Plymouth on the Massachusetts mainland. At this point we could also see dozens of spouts on the horizon, so we headed up to Stellwagen Bank where another feeding frenzy was ensuing.

Friday, May 11 brought us back to the Southwest corner of Stellwagen Bank, which seems to be the place to be if you’re a hungry humpback whale. The steep walls of the submerged bank provide the perfect opportunity for upwellings, which set off a chain reaction of productivity, moving up the food web from microscopic phytoplankton up through megafauna like baleen whales. A group of four humpbacks, including Underline, Tongs and Wizard were working together to form bubble nets—concentric rings of bubble columns which trap, stun, and confuse fish, which are then gobbled up by the bubble-blowing humpbacks.

We left this group to go investigate a splash in the distance. Another extremely active humpback was breaching, lobtailing, and rolling on its back, revealing the ventral pleats on the underside of its body extending from its chin to its navel. Whether this whale was taking a break from feeding to bask on the surface or whether it was trying to communicate with the other humpbacks in close proximity, we just don’t know. Nevertheless, it was an unbelievable week of whale watching!