Quote: Furry Logic [Chapter 3]

Furry Logic: The Physics of Animal Life - Liz Kalaugher, Matin Durrani

" Pond skaters should rejoice that water has such a high surface tension. It stops them sinking and lets them propel themselves across ponds and lakes. But pond skaters are a superficial bunch. Most animals have a much deeper relationship with water. Fish swim in it, absorbing dissolved oxygen. Hippos lead a double life, grazing on land at night but spending their days in rivers, coming up every few minutes to breathe. Crucially, mammals and birds won’t survive unless they can get water into their bodies. Even cats need to drink, despite their aversion to getting wet.


But have you ever stopped to think how you drink? For us, it’s easy. Fill a glass at the tap, grab a coffee or pour an orange juice from the fridge. Lift the vessel to your lips and pour the liquid into your mouth. Obviously without making any disgusting slurping noises; only other people do that. We’ve even got two back-up techniques. First, we’ve got a complete set of cheeks so we can make a partial vacuum in our mouths when we suck in, which is how to sup a cocktail with a straw. The pressure in your mouth is lower than outside, with the difference counteracting the force of gravity and drawing the drink up into your mouth. It’s like having your own personal vacuum cleaner. The other, rather revolting method is to put a tube in your mouth, connect a funnel to the top and ask a friend to pour the liquid in. Lean your head back and the pressure of the column of liquid forces the fluid down your gullet – ideal for students wishing to consume lots of beer as fast as possible in drunken drinking games (or so we’ve been told).


Other animals have to make do with fresh water, not beer. As it lies mostly in puddles, ponds, lakes or streams, they’ve developed a variety of strategies for supping. Pigs, sheep and horses are like us – they have complete cheeks and can drink by sucking the water up. Frogs absorb water through their skins, while the desert-dwelling Merriam’s kangaroo rat (Dipodomys merriami) extracts water entirely from the food it eats, even if fresh rainwater is about. Hummingbirds dip their tongues into nectar, with the sticky fluid flowing up grooves in the tongue like ink moving through blotting paper. As for the Namibian desert fogstand beetle (Stenocara gracilipes), it lives in one of the driest places on Earth and collects water from the fogs that drift in off the Atlantic Ocean every morning. The beetle sticks its bottom in the air so its body is at about 45° to the ground and waits for the tiny water droplets landing on its back to clump together and roll down into its mouth.


But what about cats? How they drink is a question many scientists have overlooked in pursuit of supposedly deeper quests, such as searching for the Higgs boson or designing a pen that can write in space. "