Comparison of North American Camelids with Extant Asian and South American Camelids

Part 1: Camelus vs Camelops 

Recent genetic evidence has shown that, contrary to previous belief, the extinct western camel (Camelops hesternus) of North America was much more closely related to extant camels than to llamas and alpacas. While Camelus and Llama had a common ancestor roughly twenty five million years ago, Camelus and Camelops had a common ancestor as recently as ten million years ago, placing the western camel firmly in the Camelini tribe rather than the Lamini tribe.  

The western camel was about twenty percent larger than modern Dromedary and Bactrian camels. It would have weighed as much as eight hundred kilograms and measured two point two metres at the shoulders. It is not known exactly whether or not Camelops had any humps, but if they did they may have had as many as two. The modern one-humped camel (Camelus dromedarius) has shown to have two humps as an embryo, one of which it loses before birth. Adult male dromedaries will sometimes grow a vestigial front hump as well. This suggest that having two humps (like the Bactrian camel, Camelus ferus and Camelus bactrianus) is the ancestral condition and may possibly have been shared with several ancestors and cousins of modern camels. The western camel has also been shown to have very Camelus-like feet with toes much more spayed than those of a llama. These would give good amounts of traction and support and allowed western camels to be able to travel very long distances efficiently and ergonomically, much like living camels. Their legs were similarly adapted for a long pacing gait. 

Camelops had a diet very similar to that eaten by modern camels. They ate large amounts of shrub and leaf plants, especially brush plants. Similar tooth structure to modern camels, as well as isotopic analyses, show that they were predominantly browsing herbivores, eating tough, abrasive plants avoided by horses, deer, and bison. 

Not much is known about their behaviour, but it is supposed that, like modern camels and llamas, they travelled in herds of between two and twenty animals. They would have been found in grassland, steppe, and even tundra ecosystems and shared habitat with many other herbivore species such as bison, horses, elk, and pronghorn. They would have been preyed upon by wolves, lions, cougars, and several other predators. Modern wild camels (Camelus ferus) are also sympatric with other herbivores and have been historically preyed upon by similar animals. 

All of these similarities suggest that the modern wild Bactrian camel (Camelus ferus) should be a more than adequate ecological surrogate for the extinct western camel. They share the same dietary habits, locomotive adaptations, and may have had similar behaviour. I maintain my stance that wild camels would be an excellent way to enrich Canadian biodiversity and an equally beneficial decision for wild camel conservation. 

Part 2: Lama vs Hemiauchenia 

Not much is known genetically about the large-headed llama (Hemiauchenia macrocephala), but it has been placed in camelidae family as a very close relative of modern guanacos and vicunas. In fact these modern lamine species are thought to be descended from more ancient members of Hemiauchenia.  

The large-headed llama weighed about three hundred kilograms, making it about twice as heavy as the extant guanaco (Lama guanicoe), but still less than half the size of Camelops. It had large legs that would have allowed it to reach leaves and twigs, much like guanacos and gerenuks. It also had a large, striding gait and wide-spread toes that allowed it to cover large distances over open grasslands. It is presumed that, like modern llamas, it did not have a hump or circular foot pads found in camels.  

Like modern wild guanacos and vicunas, it would have been predominantly a browser with occasional grazing habits. Like camels it would have eaten lots of brush plants but would have had more of a focus on leaves and sedge. They had very similar tooth structure to modern lamines. 

Although presumably interfertile with the sympatric western camel (much like modern camels and llamas), the species had size differences that would have prevented them from interbreeding. North American llamas would also have shared territory with many other herbivorous species such as horses, bison, and deer. Fossil evidence shows that they were preyed upon by wolves, lions, and cougars. Modern guanacos are sympatric with other camelids and deer, and are preyed upon mostly by cougars. 

I am still considering guanacos as the best possible proxy for Hemiauchenia, their smaller size being the only truly significant difference. To help alleviate this I believe guanacos from populations with the largest animals should be used. Vicunas are still a possible option due to their superior temperature adaptability, but are not favoured because of their smaller size and more mountainous habits.  

Sources 

A complete mitochondrial genome sequence of the wild two-humped camel (Camelus bactrianus ferus): an evolutionary history of camelidae 

Genomic Data from Extinct North American Camelops Revise Camel Evolutionary History 

Stable isotopes, hypsodonty, and the paleodiet of Hemiauchenia (Mammalia: Camelidae): a morphological specialization creating ecological generalization 

Last interglacial western camel (Camelops hesternus) from eastern Beringia 

http://library.sandiegozoo.org/factsheets/_extinct/camel_extinct_western/extinctcamel.htm 

http://library.sandiegozoo.org/factsheets/_extinct/llama_extinct/llama.htm 

http://library.sandiegozoo.org/factsheets/guanaco/guanaco.htm