Letter from the Desk of David Challinor
 
February 1993
 
"Camels spit when annoyed," I was told on my first camel ride in 
Egypt in 1975. until then I had thought little about these 
beasts, but the warning aroused my curiosity and reminded me that 
at the time the National Zoo had two-humped Bactrian camels on 
exhibit. The one-humped dromedary, however, is more familiar, 
not only to cigarette smokers, but to circus-goers and crowds at 
Shriner parades. 
Despite the fact that both species have lived in the Old World 
for two or three million years, all camels originally evolved in 
North America and grazed on the Great Plains until ten or twelve 
thousand years ago. They disappeared from there rather abruptly 
in what is known as the Pleistocene megafauna extinction, along 
with horses, giant ground sloths, mammoths, and wooly rhinos. 
Scientists do not know exactly what caused these mammals to 
vanish, but hypotheses abound: that they were slaughtered by the 
newly arrived humans from Asia, or that there occurred a subtle 
climate change or disease, but whatever the reason for the 
camel's disappearance from North America, they still survived 
elsewhere. Two camel groups left the New World about 3 million 
years ago, travelling in different directions: one journeyed 
west across the Bering land bridge to Asia, while another group 
migrated south about the same time across the recently formed 
land bridge (the Panamanian isthmus) to South America. 
The Asian migrants survive as two species: Camelus dromedaris 
and ~. bactrianus. The dromedary has not existed in the wild 
during historic times. Remnant herds of wild Bactrians still 
live in the Gobi desert of Mongolia and nearby China, totalling 
less than 500 animals -- legally protected but dwindling. 
The dromedary is a desert animal domesticated for 6,000 years. 
Human use of them has extended the range of dromedaries across 
North Africa and east to Turkey and Afghanistan, where their 
range overlaps that of domestic Bactrians. The two species 
interbreed but their progeny are infertile. The dromedary, with 
human assistance, continued to expand its range through the 19th 
century. Jefferson Davis, Franklin Pierce's Secretary of War 
(1853-57), imported Moroccan camels to Texas to carry supplies to 
forts along the Rio Grande. Army mule skinners had difficulty 
adapting to their new charges which, when swatted by a muleteer, 
spat at him instead of responding with a kick as had the mules. 
In frustration soldiers released many camels to wander in the 
west Texas desert; there they easily adapted to eating the 
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February 1993 Page 2 
foliage of the local plants which scientists think may have been 
present when the original camels vanished twelve thousand years 
ago. The progeny of Jeff Davis's camels survived in west Texas 
until after the turn of the century when the last feral camel was 
shot. They were unpopular with the local citizens, who claimed 
they scared their horses. 
In Australia camels were introduced in large numbers starting in 
the 1840's to explore the great central desert. They, too, were 
eventually abandoned by their owners, and having evolved to 
tolerate little rain and sparse vegetation, they have thrived in 
the remote parts of the outback. An estimated 25,000 dromedaries 
now live in an area so inhospitable to other grazers that the 
feral camels do not compete with sheep, cattle or even kangaroos 
for forage. 
scientists have long studied camel physiology to learn how they 
manage to survive such long intervals (up to 9 days) without 
water. They found that a camel's body temperature can fluctuate 
several degrees F., and thus a camel's temperature rises up to 
104 degrees F. when it gets hot, thereby reducing the need to 
sweat. The animal, furthermore, even when under stress from 
dehydration, can retain the water content of its blood, allowing 
it to circulate freely to dissipate body heat. The camel has yet 
another defense against dehydration. When low in body water, 
filtration through a camel's kidneys is reduced and sodium and 
urea concentrate in its blood at levels that would be lethal to 
other mammals. When water becomes available to a thirsty camel, 
this amazing animal can rapidly replenish its internal water 
supply by drinking up to 35 gallons in ten minutes. In humans 
and many other mammals, when the water content of blood 
decreases, blood becomes so viscous that it cannot circulate 
properly to bring body heat to the surface to cool the body 
through the evaporation of sweat. Such a failure of circulation 
leads to fatal heat stroke. 
Camels, however, have some offsetting disadvantages as domestic 
animals. Although horses, cows, and sheep are bred for various 
uses and thus appear very different from their wild ancestors, 
the camel's appearance has changed very little since 
domestication because they have not been bred for disparate 
domestic uses. Their breeding is hard to manage because a female 
does not breed until she is about 4, has ~ short annual breeding 
season (normally February and March), and has a long gestation 
(12 - 14 months). Only recently have scientists tried selective 
breeding by using artificial insemination and embryo transplants 
to produce racing camels for prosperous sheiks in the Saudi 
peninsula. The success rate of such artificial techniques is 
low, at least compared to that enjoyed by cattle breeders. 
People have been breeding cattle to be hyperfertile for thousands 
of years; further, barren cows are too expensive to keep and are 
February 1993 Page 3 
eaten, thereby removing them from the breeding population. 
Camels have evidently not been sUbject to such long-term 
selective breeding pressure for the above reasons. 
Selective breeding in the past few thousand years has been more 
successful among the North American camels that migrated to South 
America. Two wild humpless camels exist today in the high ranges 
of the Andes: the guanaco (Lama guanicoe) and the vicuna (~. 
vicugna). The domestic llama, used as a pack animal, and the 
slightly smaller alpaca, raised for its wool, are both descended 
from the guanaco, which has a longer breeding season than the 
dromedary (4 months) and a shorter gestation (11 months). The 
South American camels are well adapted to the harsh conditions of 
the altiplano -- a high elevation, treeless , rocky area. Their 
coats are thick and their flexible cushioned footpads give them 
sure footing in the rocky terrain. Split upper lips are ideal 
for grazing the short grass of the area, as well as being useful 
for spitting like their larger relatives in the Old World. 
The vicuna is the smallest South American camel and appears 
almost gazelle-like. It is fawn-colored with dainty legs and big 
eyes, and its coat can be spun into remarkably soft material. It 
is hard to shear, however, and wild animals are driven into 
stone-walled traps where they are shorn and released. The 
production of vicuna wool is labor-intensive and thus accounts 
for the luxury status of a vicuna coat or scarf. 
The use of domestic members of the camel family is becoming an 
increasing luxury throughout most of their range because they can 
seldom compete with trucks for moving cargo; they are too slow 
and have a limited carrying capacity. However, there is a 
continued demand for them in circuses, parades and recently as 
racing animals. Llamas, too, are enjoying unprecedented 
popularity as pets in North America, and there is a thriving 
market for good breeding stock. 
Zoos also play an important role in perpetuating animals 
domesticated from the wild such as camels, elephants, and llamas. 
Educating the pUblic about them increases interest in these 
useful and once economically important beasts. Zoos study these 
animals' behavior and physiology to help preserve them for future 
generations. The National Zoo, I am proud to report, has long 
been a leader in this field of research. 
As a footnote in closing, and for the sake of accuracy, the sloth 
in our Amazonia exhibit is a two-toed one, not three-toed as 
reported in my last letter. The two-toed is considerably easier 
to maintain in zoos because of its less restrictive diet. 
David Challinor 
202/673-4705