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An artist’s conception of Poebrotherium (an early camel)
Camelids are believed to have originated in North America. From there they spread down into South America (after a land bridge connected the continents) where they are represented by llamas, alpacas, vicuñas, and guanacos. Ancient camels also left North America via land bridge to Asia. The dromedary and Bactrian camels are descended from the creatures which wandered into Beringia and then into the great arid plains of Asia. Yet in their native North America, the camelids have all died out. This strikes me as a great pity because North America’s camels were amazing and diverse!
An illustration of the size of Gigantocamelus
At least seven genera of camels are known to have flourished across the continent in the era between Eocene and the early Holocene (a 40 million year history). The abstract of Jessica Harrison’s excitingly titled “Giant Camels from the Cenozoic of North America” gives a rough overview of these huge extinct beasts:
Aepycamelus was the first camel to achieve giant size and is the only one not in the subfamily Camelinae. Blancocamelus and Camelops are in the tribe Lamini, and the remaining giant camels Megatylopus, Titanotylopus, Megacamelus, Gigantocamelus, and Camelus are in the tribe Camelini.
That’s a lot of camels–and some of them were pretty crazy (and it only counts the large ones—many smaller genera proliferated across different habitats). Gigantocamelus (as one might imagine) was a behemoth weighing as much as 2,485.6 kg (5,500 lb). Aepycamelus had an elongated neck like that of a giraffe and the top of its head was 3 metres (9.8 ft) from the ground. Earlier, in the Eocene, tiny delicate camels the size of rabbits lived alongside the graceful little dawn horses. This bestiary of exotic camels received a new addition this week when paleontologists working on Ellesmere Island (in Canada’s northernmost territory, Nunavut) discovered the remains of a giant arctic camel that lived 3.5 million years ago. Based on the mummified femurs which were unearthed at the dig, the polar camel was about 30 percent larger than today’s camels. The arctic region of 3.5 million years ago was a different habitat from the icy lichen-strewn wasteland of today. The newly discovered camels probably lived in boreal forests (rather in the manner of contemporary moose) where they were surrounded by ancient horses, deer, bears and even arctic frogs! Testing of collagen in the remains has revealed that the camels are closely related to the Arabian camels of today, so these arctic camels (or camels like them) were among the invaders who left the Americas for Asia.
Aepycamelus (painting by Heinrich Harder)
The bones are a reminder of how different the fauna used to be in North America. When you look out over the empty, empty great plains, remember they are not as they should be. All sorts of camels should be running around. Unfortunately the ones that did not leave for Asia and South America were all killed by the grinding ice ages, the fell hand of man, or by unknown factors.
An artistic reconstruction of the newly discovered Arctic camels
A Crabeater Seal on an Iceberg (photo by Rob Wilson)
The crabeater seal (Lobodon carcinophagus) is a pale-colored seal which lives on the pack ice around Antarctica. Adult crabeater seals have an average length of 2.3 meters (7 and-a-half feet) and weigh around 200 kg (440 pounds) however the largest male crabeater seals can weigh up to 300 kg (660 lb). The seals’ mass alters considerably over the course of a season as they gorge themselves in preparation for lean times (or—in the case of mothers—for nursing). Like other Antarctica seals, crabeater seals have slender bodies and long snouts. They are gifted swimmers—a talent which allows them to escape their two main predators, killer whales and leopard seals. They infrequently venture beyond the continental shelves of Antarctica (although very rarely one is spotted at New Zealand, Patagonia, or South Africa). They hunt along the pack ice and travel far inland to give birth. The seals give birth to one pup annually and they can live up to 40 years.
A Crabeater Seal (Lobodon carcinophagus)
Crabeater seals can slither over land fairly well and they range farther onto continental Antarctica than any other indigenous mammal. Crabeater seal carcasses have been found up to 100 kilometers from the coast. So crabeater seals have whole swaths Antarctica to themselves (well aside from big weird penguins, lichens, and Norwegian explorers). Although they may theoretically eat a crab every now and then, the seals are misnamed. Their main prey is Antarctic krill, which they eat in huge quantities (as an aside, Antarctic krill is believed to have the greatest biomass of any single species on Earth). Although they do not have baleen like the great rorquals, crabeater seals have specialized krill-filtering cusps on their teeth which trap the krill and allow water to escape. When krill are not available, the seals can also feed on fish and squid.
Crabeater Seal Teeth
Perhaps the most remarkable thing about crabeater seals is their sheer numbers. Other than humans (and our livestock) they are the most numerous large mammals on the planet. Caribou and wildebeests exist in herds of hundreds of thousands, but the crabeater seal population numbers in the millions. The full population of crabeater seals is unknown. Estimates range from 7 million to 70 million. Since they are pale colored seals darting between the crushing pack ice of an uninhabited continent we have a population estimate which is off by a factor of ten. The fact that so few people have seen them might explain why they are still so successful.
A Crabeater Seal enjoys sunbathing on a southern beach.
Adult female Cuvier’s beaked whale (Ziphius cavirostris). Photo by Robin Baird.
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.
Small Beaked Whales (an illustration by Brett Jarrett)
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.
Sowerby’s Beaked Whale (Mesoplodon bidens)
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.
(Photo: credit Nan Hauser & Hoyt Peckham, CCRC)
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.
Wild Turkey (Meleagris gallopavo)
My posts about animals are based on personal favorites but I have also tried to choose categories of animals in a manner which reveals something larger about zoology and taxonomy. You have probably noticed that my featured creatures are not arbitrary but are arranged taxonomically according to Linnaean hierarchy in the manner which follows:
- Phlylum: Mollusca
- Class: Mammalia (mammals)
- Order: Siluriformes (catfish)
- Suborder: Serpentes (serpents)
- Genus: Meleagris (turkeys)
I have not written about a family yet because I was leaving myself some room for the future (feel free to make suggestions). Additionally, I have only written glancingly of kingdoms or domains because those overarching categories are far too large and baffling for me to deal with meaningfully (although I would probably choose the domain “bacteria” if I had limitless time, resources and a great deal more knowledge and intelligence). The missing bottom category of species is always applicable to whatever the featured species of the day is (or, in a pinch, to Homo sapiens, the dark meddlesome, magnificent species behind history, art, politics and other non-animal, non-plant topics over there in the category cloud).
Not only have I have chased the representative members of my chosen taxonomic categories through art, mythology, and anecdote, I have also tried to write as cogently as I am able about their behavior, biology, and morphology (biologists and morphologists are no doubt laughing into their hands right now, but, hey, you guys are not always the most compelling or comprehensible writers, so give me a break). Also, I understand that traditional hierarchy is coming to be re-assessed in light of new genetic evidence and the innovative ideas of cladistics: maybe my categories were already hidebound to start.
Western Coral Snake (Micruroides euryxanthus) photo by David M. Dennis
I mention all of this because I am beginning to feel pinched by some of my categories. I could write about a different obscure catfish, or dig up a new catfish recipe but is that really what people want? I still have a few more turkey stories to write and no doubt more information will come to me (probably around Thanksgiving), but I am running out of things to say about my favorite bird. Should I disloyally choose a new genus to pursue. Do you want to hear more about tiny obscure catfish? I could drop it all and move to entirely new topics, but I don’t feel right about that yet. Maybe some reorganization is needed when I launch the redesigned version of Ferrebeekeeper in the near future.
Any insight or feedback would be appreciated. I’m sorry for the informal first person tone of this post but I am traveling today and don’t have time to research an appropriate column. Also catfish and turkey fans should not give up yet, I still have a handful of ideas left about those magnificent creatures (not to mention a stirring Siluriforme overview).
Thanks.
Lima Shovelnose Catfish (Sorubim lima)
A Dugong and Diver (photograph by Duane Yates)
There are about 120 living species of marine mammals (although that total may tragically become much smaller in the very near future). Of this number, only one species is herbivorous. The mighty dugong (Dugong dugon) is the last animal of its kind, a gentle lumbering remnant of the giant herds of sirenian grazers which once graced the world’s oceans. Dugongs are distinct from the three extant species of manatees (the world’s other remaining sirenians) in that they never require fresh water at any point of their lives. Additionally dugongs possess fluked tails in the manner of dolphins and whales.
Dugong Range
Dugongs live in shallow tropical waters of the Indian Ocean and the Pacific Ocean. They range from Madagascar to the Philippines, but are only common along the north coast of Australia (where conservation efforts and a limited human population have allowed them to live in peace). Dugongs can swim in deep oceans for a limited time, but prefer to stay on continental shelves where they can feed on seagrass and marine algae. Their all-salad diet does not prevent them from growing to substantial size: some individuals have been known to reach more than 3.5 meters in length (11 feet) and weigh over 950 kilograms (nearly a ton). Although Dugongs can live more than seventy years, they reproduce extremely slowly. Females gestate for over a year and then suckle their calf for around 18 months. Calves may stay with their mothers for many years after being weaned and need almost contact with their mothers for security and affection until they are almost grown. Young dugongs swim with their short paddle-like flippers, but adults use their tail for propulsion and only steer with their flippers.
Dugong and Calf
Dugongs have a variety of vocalizations with which they communicate. Usually they live in small family units. Great herds are not unknown but seagrasses do not grow in sufficient quantity to support such numbers together for long.
Like the other sirenians, Dugongs have dense bones with almost no marrow (a feature known as pachyostosis). It has been speculated that such heavy skeletons help them stay suspended just beneath the water in the manner of ballast. The lungs of dugongs are extremely elongated, as are their large elaborate kidneys (which must cope with only saltwater). Additionally, the blood of dugongs clots extremely rapidly.
Dugongs face a number of natural threats, particularly storms, parasites, and illnesses. Because of their large size they are only preyed upon by alpha predators such as large sharks, killer whales, and salt-water crocodiles. As with other marine animals, the greatest dangers facing dugongs come from humankind. For millennia Dugongs have been hunted for meat, oil, and ivory. Traditional medicine from various portions of their range (wrongly) imputes magical properties to parts of their bodies. Worst of all, dugongs are frequent victims of boat collisions or are killed as by-catch by fishermen trying to catch something else.
Close-up of a Dugong (Julien Willem)
The Eocene (Illustration by Bob Hynes for the Smithsonian Institution)
The Eocene epoch (which lasted from 56 million ago to 34 million years ago) was hot! Temperate forests ran all the way to the poles. Steamy tropical jungles grew in the latitude where Maine is now and the equatorial regions of earth were (probably) sweltering. Tropical reefs formed in the coastal waters around a heavily forested and ice-free Antarctica. Since there was not year-round ice at each pole, the sea levels were much higher.
A Global Map of the Early Eocene (map by Dr. Ron Blakey)
The Eocene was a time when most of the contemporary mammalian orders first appeared. The earliest artiodactyls, perissodactyls, rodents, bats, probiscideans, sirenians, and primates all originated during this time. Of course mammals were not the only story: the Eocene was also a time of great diversification for birds and many familiar orders of avians developed then. Reptiles begin to put the setbacks which marked the end of the Cretaceous behind them and several giant new species emerged including an immense tropical ur-python and a host of crocodiles and turtles. It is harrowing to think that the first wee dawn horses and cute little early atiodactyls were forced to contend with a 13 meter long super snakes and giant crocodilians (which flourished in the great hot swamps of Alaska), but such is the case.
Titanboa with Ancient Crocodilian (painting by Jason Bourque)
The high temperatures of the Eocene are perplexing to scientists. By contrast, the temperatures of the Paleocene (which was the first era of the Cenezoic and had directly preceded the Eocene) were much more temperate. In fact the temperature spike of 56 million years ago seems to have ended the Paleocene and brought about the diversification of Eocene life. The rapid warming is known as the Palaeocene-Eocene thermal maximum and scientists have been vigorously debating what caused the climate change. An immense amount of carbon seems to have entered the atmosphere at this time, which in turn led to greenhouse warming. It remains controversial as to how such a large quantity of carbon got into the atmosphere. Comet/meteorite impact, massive peat fires, and volcanic activity have been suggested as triggers, however supporting evidence is lacking. The release of globally significant quantities of hydrocarbons–which had been trapped in undersea clathrates seems like a more feasible hypothesis, as does the idea that the earth’s orbit brought the planet closer to the sun for a time.
Phenacodus, a goat-sized grazer of the Eocene era (painting by Heinrich Harder)
The end of the Eocene was also linked to the carbon cycle. Reduced carbon dioxide in the atmosphere seems to have led to global cooling and newly evolved varieties of grasses began to invade large swaths of the world. Additionally two massive meteor strikes in Siberia and Maryland combined with substantial volcanic activity to finish off the long hot summer. But during the Oligocene, the era which followed the Eocene, the world was a much more familiar place inhabited by orders of animals which are still here with us today (or are us–since primates first evolved during the Eocene).
