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The National Zoo in Washington D.C. has a duck pond over by the parking lot entrance. There are numerous pretty North American ducks in the pond as well as mute swans from Europe, black swans from Australia, and various fancy ducks from around the globe–but these beautiful waterfowl pale in comparison to lions, pandas, and elephants–so visitors are inclined to rapidly push by the little lake. One day (when I too was rushing by) I noticed a ghostly white presence flitting around the bottom of the pond. At first I thought I was hallucinating and then I thought that a penguin or puffin had escaped the Arctic area. It was an amazingly dexterous aquatic hunter swimming underwater hunting for small fish. I watched for some time before it popped to the surface and revealed itself to be…a male smew!
Smews (Mergellus albellus) are the world’s smallest merganser ducks. They may seem alien because, for modern birds, they are ancient. Fossils of smews have been found in England which date back to 2 million years ago. The smew is last surviving member of the genus Mergellus—which includes fossil seaducks from the middle Miocene (approximately 13 million years ago). Smews breed along the northern edge of the great Boreal forests of Europe and Asia. During winter they fly south to England, Holland, Germany, the Baltic Sea, & the Black Sea. Like other Mersangers, smews are hunters: they dive underwater and deftly swim down fish (showing ballet-like grace during the process). Like many other sorts of piscivorous hunters, smews have heavily serrated beaks (which are further specialized with a wicked hooked tip).
The drake smew has been poetically described as having the combined appearance of cracked ice and a panda. Female smew ducks are plainer—they have gray bodies, chestnut crowns and faces, and a white neck. Although smews are from an ancient lineage and live in a difficult part of the world, they are still not doing badly. Their numbers have declined somewhat, but they are not endangered (which is good news because they are very lovely and captivating).
There are entire species of large mammals living today on Earth which have never been seen alive by humans. Even though they can grow larger than elephants, their numbers and habits are unknown. We might not even know all extant species in the family. These mystery mammals are the beaked whales (family Ziphiidae) masters of deep ocean diving. The family is comprised of at least 21 different species, only 3 of which are well known (thanks to whale hunting in previous centuries). Beaked whales are poorly understood because they are rarely on the surface of the ocean where we can observe them. They are capable of diving more than 1,899 meters (6,230 feet) and can stay underwater for almost an hour and a half. Beaked whales live in the black–down among the underwater seamounts, canyons, and abyssal plains. We only know them from the examination of dead specimens: indeed, for some species of beaked whales that is quite literally true and they have only been seen when dead.
Beaked whales grow to sizes of 4 to 13 metres (13 to 43 ft) depending on the species. They are sexually dimorphic—the males are a different size than the females. Additionally male whales have prominent domed foreheads and a pair of fighting teeth for dueling and sexual display (these teeth do not fully develop in females). Beaked whales feed on squid, and, to a lesser extent, fishes and invertebrates which they capture from the ocean bottom by means of suction. In order to produce this suction effect, the whales have highly nimble tongues and throat grooves.
The most distinctive features of beaked whales (save perhaps from their rostral “beaks”) are the body features which allow them to dive so deeply and then hunt in the dark crushing waters. The lungs of beaked whales collapse at a certain pressure—most likely as a way to minimize the dangers of nitrogen transfer. Their livers and spleens are huge in order to deal with the dangerous metabolic bi-products of prolonged periods when they are unable to breathe. Additionally, their blood and muscle tissue is capable of capturing and storing substantially greater quantities of oxygen than the tissue of other mammals. Beaked whales can pull their pectoral flippers into grooves which run along the sides of their bodies and thus become more streamlined.
In order to find their way in the deep ocean, the whales rely on sophisticated acoustic echo-location organs. Lips behind the blowhole produce high pitched vibrations which bounce off of prey and obstacles. Echoes from these vibrations are then picked up and focused into the whales’ sensory organs by special fat deposits and bone structures. Unfortunately this method of echolocation seems to make beaked whales extremely sensitive to sonar. Resurfacing whales are unable to avoid the amplified sound waves and can suffer injuries to their sensory organs (or even to their large delicate livers). Additionally, it is theorized that Beaked whales may try to resurface too quickly to avoid sonar and therefore risk decompression sickness.
Humankind has also been fishing ever deeper waters as fish stocks crash—which involves the whales in by-catch issues. Hopefully we will learn more about this family of enigmatic divers (and become more responsible stewards of the ocean) so that the beaked whales do not vanish before we even get to know them.
The great Southern Ocean which swirls in a clockwise circle around Antarctica is home to many of the Earth’s largest animals. Blue whales come here to gorge on vast schools of krill. Among the icebergs and the towering waves, southern elephant seals (the largest member of the order Carnivora) fight duels to build their harems, and highly intelligent killer whales hunt together in pods. There are populations of sperm whales living in the Southern ocean as well and these leviathans dive to the cold floor of the world hunting for the world’s largest mollusk, a huge cephalopod which can only be found in the Southern Ocean. In fact this bizarre creature, the colossal squid (Mesonychoteuthis hamiltoni) is also the world’s largest invertebrate. Also known as the Antarctic squid or the giant cranch squid, the colossal squid lives in the abyssal depths. Unlike other squid, the colossal squid does not have tentacles–its powerful arms are studded with sharp hooks (much like the long-extinct belemnites). Some of these hooks swivel while others have three barbs in the manner of a fish spear.
The measurements of the colossal squid are staggering. Its eye alone (the largest of any known creature) measures 27 centimetres (11 in). A fully grown adult squid is estimated to be 12–15 metres (39–49ft) long. Although giant squid have longer tentacles, the colossal squid a long stout mantles and are thus much more massive. Their upper weight limits are unknown but are well over 500 kg (+1000 lbs).
The colossal squid is believed to be an ambush predator, which lurks in the depths waiting for chaetognatha, other squid, and benthic fish (such as the Patagonian toothfish) to pounce upon. It is hypothesized that they have a slow metabolism and do no need great reserves of food (unlike the energetic endothermic sperm whales which prey on them). The colossal squid are believed to be sexually dimorphic—the females become much larger than the males.
There is a reason that so much of this article is couched in ambivalent language such as “estimated”, “believed” and “probably”: colossal squid live in an environment where humankind can barely venture. The colossal squid are fast enough and clever enough to usually evade our nets, lines, and traps (although fishermen trying to catch Patagonian toothfish hooked a 450 kg (990 lb) specimen which was about 39 feet (13 m) long). Additionally our submarines and submersible robots are too slow and noticeable too stalk the squid in the abyssal depths. Other ocean creatures do not suffer from the same problem. Juvenile colossal squid are eaten by beaked whales, elephant seals, sharks, toothfish, and even albatrosses, however the adult squid are so large that only massive sleeper sharks and giant sperm whales can threaten them. Sperm whales are often covered with scars from their battles with the giants but the whales easily have the upper hand. Sperm whale stomachs have been found filled with hooks and beaks (which coincidentally were much larger than those found on the largest squid specimens recovered by humans to date).