In our last Winter/Spring 2013 lecture at the Orleans Yacht Club, Peter Trull spoke about “The Symbiotic Relationship between Humpback Whales and Marine Birds”. Trull has been involved in education and research for about 35 years. Some notable work includes: coordinating the Audubon Society’s Coastal Seabird Monitoring Program; conducting research trips to Guyana to study various species of terns, plovers, and sandpipers; serving as the education director at both the Cape Cod Museum of Natural History and the Provincetown Center for Coastal Studies; teaching seventh grade science at the Cape Cod Lighthouse Charter School and authoring 5 books on a variety of nature-related subjects.
Trull began his talk somewhat jokingly, with a request of all his listeners to “Go east, more than you do”. Trull’s point was that although we live on one of the easternmost points of the United States, there is much more to see and appreciate just beyond the coast of our own Cape Cod.
Before explaining the specific nature of their symbiotic relationship with marine birds, Trull helped to give us a better understanding of Humpback Whales. In their animal classification, they are of the order Cetacea, suborder Mysticeti. This suborder contains all of the baleen whales, the “-ceti” suffix in their suborder name referring to whales, and the “mysti-” prefix meaning mustache, referencing the appearance of the baleen that early fishermen saw as similar to that of a human mustache.
These whales spend summers in the cooler waters near the Cape and winters in more tropical areas. Another interesting fact Trull provided is that these whales, being mammals with lungs similar to ours, are unlike humans in that they are voluntary breathers. This means that they have to put a conscious effort into breathing, whereas humans generally breathe “automatically”. . If you’ve ever been on a whale watch trip and seen a whale breach and watched the spray erupt from the top of its head, you have seen a whale breathe. It is also interesting to note that they utilize more of their lung capacity on each breath than we do, filling their lungs up to ~80% capacity, compared to humans who typically utilize only ~15% capacity on any given breath.
Humpback Whales feed primarily on sand eels (also known as sandlances), this food source is what leads to their interesting relationship with marine birds.
To better illustrate this relationship, Trull outlined the three types of symbiosis: mutualism, commensalism, and parasitism. If you think of mutualism as mutually beneficial, and parasitism as one benefitting at the cost of the well-being of the other, commensalism falls right in between. Commensalism is a type of symbiotic relationship where one species will benefit while not affecting the other species in a positive or negative way. The relationship between Humpback Whales and marine birds is an excellent example of commensalism.
Humpback Whales will consume up to 1 ton of sand eels every day. The primary way that these whales feed is known as “bubble feeding”: the whales use their blowholes to send these massive bubbles of air up to the surface of the water, forcing any sand eels in that direct area upward.. When a large school of these fish is located near the surface of the water, the whales will then rise up with their mouths agape and take in mouthfuls of them. This method is particularly effective for the whales to consume the food they need to survive, but it also benefits other species as well.
Closer to the shore, gulls such as herring or laughing gulls will take advantage of these large schools of fish conveniently located right at the surface because of the whale’s behavior. Farther out at sea however, other birds will also get in on the feeding frenzy. The term marine bird refers to birds that we really do not see on the Cape, because they typically nest on islands very distant to us,and when they are in the waters surrounding Cape Cod, they have no reason to come to land. These birds are so perfectly adapted to the conditions of the oceans, including the ability to get all the food they need, that they spend all their time at sea. Common examples of these pelagic birds include: great shearwaters, sooty shearwaters, and Cory’s shearwaters. The great shearwaters nest far south on islands off the southern coasts of South America and Africa, and spend summers in the waters around the Cape. As Trull noted in reference to their migration, “these birds see more places in half a year than most humans see in a lifetime”.
All these birds, the gulls and the shearwaters, will often be seen whenever groups of whales are feeding, simply taking advantage of the fact that the whales’ feeding technique provides such an abundance of their favorite food. On whale watches, such as those from the Dolphin Fleet in Provincetown, it is a common occurrence to see large flocks of these birds at the same time, in the same area, as the whales that are the targets of the excursions.
Trull ended his talk with some cautious words but also encouragement, on the topic of whale watching. With so many people having boats here on Cape Cod, it’s not uncommon for people to try to get in on the action that whale watchers are seeing, but these smaller boats can cause serious harm to the whales. Upon showing graphic photos of injured whales, he stressed that if individuals are attempting to see whales from their own boats, once within half a mile of a whale watch boat or upon seeing whales, they should shut off their engines. With whales often feeding at the surface, the propellers on engines can pose a threat to the well-being of the whales.
On that note though, he encouraged people to come to the Dolphin Fleet whale watches, to get the most out of an excursion with a properly trained crew and educated guides in order to make it a safe, educational trip. He suggested calling ahead, to see if it’s a good day for sightings, and even to determine the types of whales being sighted as well. If the fleet tells you that they’re seeing Minke and Finback whales, the sighting of a Humpback is unlikely.
As Trull suggested, “Go east!”