Rob-servations #3: Blue whale identification
by Rob Nawojchik During our 12-day trips to Baja, we are very fortunate to see blue whales on most trips. Blue whales are the largest animals to ever live on Earth, and even veteran whale watchers are stunned by their presence. Unfortunately, blue whale populations were severely decimated by industrial whaling. The good news is that, now that they are protected worldwide, their numbers are starting to trend upwards. The eastern North Pacific population of blue whales (the group which includes the Baja blue whales) is among the healthier populations and seems to be increasing. In contrast, the North Atlantic population (a group with which I’m familiar from my marine mammal stranding days) remains at low levels. Today we’ll focus on the identification (ID) characteristics of blue whales, using the ID categories I mentioned in the last blog. One caveat before we begin: many of the ID descriptions I’ll be using are relative terms, terms such as larger vs. smaller, taller vs. bushier, pronounced vs. modest, etc. When first starting out on your inaugural whale watch, it probably doesn’t help you when you say, “How do you know it’s a blue whale?” and the naturalist says, “Well, for one thing, it’s a lot bigger than a humpback.” When seeing your first whale, how big is “big”? What does “big” look like on the ocean when you’re seeing a tiny fraction of the whale? What does “big” look like from three miles away? The best remedy for this dilemma is repetition. By observing many whales every day, you too will soon appreciate the subtle (at times) differences that allow us to identify whales at sea. A reminder: we are focusing only on species found in Baja. By eliminating non-Baja species from our identification algorithm, we can more quickly hone in on the ID. Size and shape of spout/blow: Befitting the largest whale in the world, the blue whale has the tallest spout. The blow can be seen from miles away. Also, the blow is roughly columnar in shape, as opposed to the more-bushy blow of a humpback, the heart-shaped blow of a gray whale, or the angular blow of a sperm whale. The spout of a whale is heavily affected by wind, so on windy days the blow tends to get “knocked-down” and is not as obvious, or at least not as stereotypical in size and shape. Size of animal: As mentioned, this is the largest species of whale. Adults in the Northern Hemisphere typically range from 75 to 90 feet long (~23-27m). There is some size overlap with the fin whale, but a large blue whale is larger than a large fin whale. A good rule of thumb: if the whale is over 50 feet, then it will be either a blue whale or a fin whale (note: male sperm whales can get over 50 feet, but we’ll account for them in a different blog). Color: The color of a whale, although often diagnostic, will vary dramatically depending on light conditions. The relative position of you, the whale, and the sun will affect your perception of the color. Also, the whale’s color will appear different on sunny vs. overcast days. The color of the blue whale is best described as a mottled blue-gray. The mottled nature of the pigmentation pattern will probably best help you in separating the blue whale from the color pattern of other large whales. Dorsal fin: The placement of the dorsal fin on the blue whale is far back on body. Typically, during a surfacing, you will first see the head and blowhole, then the back, eventually the dorsal fin, and finally (sometimes) the tail flukes. Usually the head has already re-submerged by the time the dorsal fin is seen. This is in contrast to some other species in which you may see the head and dorsal fin at the same time. The shape of the dorsal fin in the blue whale is variable, but ranges from triangular to “falcate” (curved, in a similar fashion to a dolphin’s dorsal fin). Perhaps the most distinguishing feature of the blue whale dorsal fin is its comically small size. For such a large whale, the fin is disproportionately modest. Tail flukes: When discussing the flukes, the first consideration is behavior. Some species sometimes (but not always) show their flukes when they dive. Other species (almost) never do. Thus, when you see a whale’s flukes, even from a distance, you can narrow down the identification. Blue whales are among those species that sometimes show their flukes. The second consideration is size and color pattern. Blue whales have broad tapered flukes with a smooth trailing edge. They tend to have a uniform gray color, with maybe some lighter streaking. In subsequent blogs, we’ll see how the flukes of other species differ from the blue whale. Species-specific traits: For the blue whale, I think the two unique characters that stand out are the extreme size and the mottled color pattern. Behavior: Many of the blue whales we see in Baja display the “typical” baleen whale dive pattern: about three to five blows while swimming near the surface, then a dive of about 10-15 minutes. As mentioned, they sometimes show their flukes when diving. We have encountered some blue whales whose dive times were much longer than 15 minutes. In general, we do not see blue whales exhibit some of the behaviors that we’ll discuss with other species, behaviors such as spy-hopping, lob-tailing, breaching, or pectoral-flipper slapping.
