Very Interesting – July-August 2019

Why do young children

pick their noses and

eat it?

Becca Jubber, Alberton

GETTY X5 ILLUSTRATION: PETER SUCHESKI

Why do elephants have

such wrinkly skin?

Lydia Erasmus, Cape Town

T

he African elephant’s wrinkly skin

was recently put under the

microscope by researchers in

Switzerland. They found that the wrinkles

are actually a complex web of

‘microvalleys’ formed as the outermost

skin layer (epidermis) thickens and

bends with age, causing it to crack. This

fissured skin surface retains five to 10

times more water than a smooth

surface, which helps to keep the

elephant cool as the moisture (from rain

or mud) evaporates from the cracks.

Unsurprisingly, Asian elephants have

smoother skin than their African

cousins, as they live in wetter

environments and have less trouble

keeping cool.

E

veryone – adults and children alike –

occasionally picks their nose to free up the

passages. In fact, the diameter of our nostrils has

probably evolved to match our finger size, for this

reason. Children often eat their bogies because they

are curious, and it’s a convenient method of

disposal. There’s no particular medical or dietary

advantage, but eating bogies is harmless.

I

t’s theoretically possible for dogs, but difficult in practice. Dogs have

co-existed with humans for at least 14,000 years and have evolved

some extra digestive enzymes that help them to digest plant starches,

probably as a result of sharing our food. But a 2015 study at the

University of California, Davis, found that 25% of commercial vegetarian

dog foods lacked the right balance of essential amino acids. And

homemade diets are even worse: a 1998 study found that 50% of dogs

fed homemade vegetarian or vegan food had dietary deficiencies.

For cats, it is even harder to balance. Cats are entirely carnivorous

in the wild, and there are several amino acids only found in meat,

such as taurine, that they can’t synthesise or store, so a vegan cat

diet has to be carefully tailored to their age and body weight. Too

little taurine can cause blindness and heart failure, while too much

can lead to serious urinary tract infections. Carnivorous cats absorb

all the taurine they need from meat, but synthetic taurine added to

vegan food comes in several different forms, which are absorbed by

the cat’s metabolism at different rates. This makes it extremely

difficult to give cats a balanced vegan diet.

Can I raise my dog or cat as

a vegan? Anele Biyase, Durban

Q&A

Questions & Answers

Got questions you’ve been carrying

around for years? Very Interesting

answers them! Mail your questions

to [email protected]

A The first dog

biscuits were

manufactured by Ohio

entrepreneur James

Pratt after he saw

sailors feeding their

pets ‘hard tack’

(made of flour, water

and salt) in England.

A Grapes and raisins

can promote kidney

failure in dogs.

Q

&

A

FLASH