Know your camel
The camel may be the pin-up of the Silk Road, but the two-humped Bactrian camel, with its scrawny legs, ungainly walk and hairy humps, is far from a sexy beast.
A fully grown adult camel can stand well over 2m tall, but chooses to mate sitting down. The male has a large, inflatable sack in its neck, an organ called a dulla. When in rut it extrudes from his mouth like a long, swollen, pink tongue in a bid to assert dominance and attract the glances of a passing female. When he finally catches her eye (possibly having pursued her at speed across the steppe: be warned if you're riding on top), they mate sitting side by side; in a single mating session, the male ejaculates three or four times in succession.
It's not only their sexual habits that make camels intriguing; they also have a number of physiological adaptations to help them live in dry climates. Camels'humps don't actually contain water, as was once commonly believed, but concentrated body fat. When this fat is metabolised, it releases more than 1g of water for every gram of fat. Unlike other mammals, a camel's red blood cells are oval rather than circular, which helps them flow when the body is dehydrated and also makes them less likely to rupture when large quantities of water are finally consumed. Consequently a camel can drink as much as 70 litres of water per minute, taking on 200 litres in total. Camels rarely sweat, even when temperatures reach 50°C, and when they do sweat they can lose up to 25% of their body weight before circulatory disturbance results in cardiac arrest. When a camel breathes out, water vapour is trapped in its nostrils and is then reabsorbed. They can, in fact, ingest sufficient moisture from eating green foliage to remain hydrated without drinking water at all.