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Blainville's Beaked Whale

(Mesoplodon densirostris)

The Blainville's beaked whale is sometimes called the dense-beaked whale. Many of the beaked whales or "ziphiids" are so difficult to observe that some of the 20 species have never been seen alive, and everyone expects that more species will be identified. They all have two grooves on their throats, assumed to help them suck in prey like squid. They also have shallow "pockets" or depressions to tuck in their pectoral fins, probably to reduce drag as they dive. Many species used to be known visually only by the size, shape and location of the teeth in adult males, and many records were uncertain unless an expert measured their bones. Today size, coloration, habits, location, and genetics all help to tell species apart. Only an expert can tell that this is an immature male from the shape of his lower jaw. If he was mature you would see a much more dramatic arch, with a single tooth at the forward point of each jaw. These teeth are also called tusks, because they are used in conflicts, creating the line scars most of these whales show. (Photo courtesy Colin D. MacLeod, UK.)
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This baby Blainville's beaked whale surfacing alongside her mother is not even a day old, with visible fetal folds and the floppy dorsal fin typical of newborn cetaceans. She looks far smaller than the 2 m length at birth quoted in books. She seems to be lunging up; learning how to surface to breath efficiently must be a struggle, even in these calm waters. If her mother dives for the normal 20-45 minutes to find food, is the calf left at the surface alone or watched over by another whale? How do the mother and calf find each other later? So much to learn, for her and for us. We don't even know how long these whales live. (Photo courtesy Colin D. MacLeod, UK.)
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The typical dorsal fin of the Blainville's beaked whale looks likes so many other species that it's no wonder they can be nearly impossible to identify at sea. One view of his jaw would tell an expert this was an adult male, by the shape and location of his two tusks. Most of these whales show small oval scars from small cookie-cutter sharks that attack many deep diving cetaceans, attaching themselves by suction just long enough to bite and spin, tearing out a small piece of flesh. (Photo courtesy Colin D. MacLeod, UK.)
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Seeing a small whale surface sharply, with jaw pointed out of the water at an angle, usually means a beaked whale, but which one? This Blainville's beaked whale shows the characteristic slightly arched jaw of an adult female. Although most often light bluish gray above, with light gray beneath, some of their heads are brownish. Notice the hump behind her head from bending her neck up to breathe. Even an expert would have trouble identifying her, as females of many species look alike. She doesn't need teeth to catch her prey, such as squid, that migrate daily up and down deep ocean slopes. But she must dive very deep and often, in calm or stormy waters, and be able to find her prey in absolute darkness. Some day scientists will show us how this whale can echolocate efficiently, even if she doesn't have the huge melon we would expect. And why are beaked whale skulls so asymmetrical? (Photo courtesy Colin D. MacLeod, UK.)
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Other identification clues would be the whale's length, about 15 feet (5 m) long, and location. But since Blainville's beaked whales are found in tropical and warm temperate regions of all oceans, usually in waters with slopes from 1,600-3,300 feet (500-1000 m), they must share habitats with other beaked whales. Blainville's beaked whales may be the most widespread and easily approached of the 14 known Mesoplodon species. Most beaked whales seem to prefer steep, deep slopes for feeding, but has this isolated different populations? Future genetic testing may confirm this, but isolation means some populations are more vulnerable to humans than others, and once gone may be lost forever. Blainville's beaked whales were killed by navy sonar in the Bahamas in 2000, and may have been sonar victims many times before. The chances of finding these dead or dying whales is very slim, so how do we know how many have died, and how to prevent such tragedies in the future? We hope someone sees Blainville's beaked whales in that part of the Bahamas again, which would mean that some survived. (Photo courtesy Colin D. MacLeod, UK.)
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